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Copyright © 2011 Red Hat Inc.
Abstract
The User manual is an in depth manual on all aspects of HornetQ
Copyright © 2010 Red Hat, Inc. and others.
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What is HornetQ?
HornetQ is an open source project to build a multi-protocol, embeddable, very high performance, clustered, asynchronous messaging system.
HornetQ is an example of Message Oriented Middleware (MoM) For a description of MoMs and other messaging concepts please see the Chapter 4, Messaging Concepts.
For answers to more questions about what HornetQ is and what it isn't please visit the FAQs wiki page.
Why use HornetQ? Here are just a few of the reasons:
100% open source software. HornetQ is licenced using the Apache Software License v 2.0 to minimise barriers to adoption.
HornetQ is designed with usability in mind.
Written in Java. Runs on any platform with a Java 6+ runtime, that's everything from Windows desktops to IBM mainframes.
Amazing performance. Our ground-breaking high performance journal provides persistent messaging performance at rates normally seen for non-persistent messaging, our non-persistent messaging performance rocks the boat too.
Full feature set. All the features you'd expect in any serious messaging system, and others you won't find anywhere else.
Elegant, clean-cut design with minimal third party dependencies. Run HornetQ stand-alone, run it in integrated in your favourite JEE application server, or run it embedded inside your own product. It's up to you.
Seamless high availability. We provide a HA solution with automatic client failover so you can guarantee zero message loss or duplication in event of server failure.
Hugely flexible clustering. Create clusters of servers that know how to load balance messages. Link geographically distributed clusters over unreliable connections to form a global network. Configure routing of messages in a highly flexible way.
For a full list of features, please see the features wiki page .
The official HornetQ project page is http://hornetq.org/.
The software can be download from the Download page:http://hornetq.org/downloads.html
Please take a look at our project wiki
If you have any user questions please use our user forum
If you have development related questions, please use our developer forum
Pop in and chat to us in our IRC channel
Our project blog
Follow us on twitter
HornetQ Git repository is https://github.com/hornetq/hornetq
All release tags are availble from https://github.com/hornetq/hornetq/tags
Red Hat kindly employs developers to work full time on HornetQ, they are:
Clebert Suconic (project lead)
Andy Taylor
Howard Gao
Francisco Borges
And many thanks to all our contributors, both old and new who helped create HornetQ, for a full list of the people who made it happen, take a look at our team page.
HornetQ is an asynchronous messaging system, an example of Message Oriented Middleware , we'll just call them messaging systems in the remainder of this book.
We'll first present a brief overview of what kind of things messaging systems do, where they're useful and the kind of concepts you'll hear about in the messaging world.
If you're already familiar with what a messaging system is and what it's capable of, then you can skip this chapter.
Messaging systems allow you to loosely couple heteregenous systems together, whilst typically providing reliability, transactions and many other features.
Unlike systems based on a Remote Procedure Call (RPC) pattern, messaging systems primarily use an asynchronous message passing pattern with no tight relationship between requests and responses. Most messaging systems also support a request-response mode but this is not a primary feature of messaging systems.
Designing systems to be asynchronous from end-to-end allows you to really take advantage of your hardware resources, minimizing the amount of threads blocking on IO operations, and to use your network bandwidth to its full capacity. With an RPC approach you have to wait for a response for each request you make so are limited by the network round trip time, or latency of your network. With an asynchronous system you can pipeline flows of messages in different directions, so are limited by the network bandwidth not the latency. This typically allows you to create much higher performance applications.
Messaging systems decouple the senders of messages from the consumers of messages. The senders and consumers of messages are completely independent and know nothing of each other. This allows you to create flexible, loosely coupled systems.
Often, large enterprises use a messaging system to implement a message bus which loosely couples heterogeneous systems together. Message buses often form the core of an Enterprise Service Bus. (ESB). Using a message bus to de-couple disparate systems can allow the system to grow and adapt more easily. It also allows more flexibility to add new systems or retire old ones since they don't have brittle dependencies on each other.
Messaging systems normally support two main styles of asynchronous messaging: message queue messaging (also known as point-to-point messaging) and publish subscribe messaging. We'll summarise them briefly here:
With this type of messaging you send a message to a queue. The message is then typically persisted to provide a guarantee of delivery, then some time later the messaging system delivers the message to a consumer. The consumer then processes the message and when it is done, it acknowledges the message. Once the message is acknowledged it disappears from the queue and is not available to be delivered again. If the system crashes before the messaging server receives an acknowledgement from the consumer, then on recovery, the message will be available to be delivered to a consumer again.
With point-to-point messaging, there can be many consumers on the queue but a particular message will only ever be consumed by a maximum of one of them. Senders (also known as producers) to the queue are completely decoupled from receivers (also known as consumers) of the queue - they do not know of each others existence.
A classic example of point to point messaging would be an order queue in a company's book ordering system. Each order is represented as a message which is sent to the order queue. Let's imagine there are many front end ordering systems which send orders to the order queue. When a message arrives on the queue it is persisted - this ensures that if the server crashes the order is not lost. Let's also imagine there are many consumers on the order queue - each representing an instance of an order processing component - these can be on different physical machines but consuming from the same queue. The messaging system delivers each message to one and only one of the ordering processing components. Different messages can be processed by different order processors, but a single order is only processed by one order processor - this ensures orders aren't processed twice.
As an order processor receives a message, it fulfills the order, sends order information to the warehouse system and then updates the order database with the order details. Once it's done that it acknowledges the message to tell the server that the order has been processed and can be forgotten about. Often the send to the warehouse system, update in database and acknowledgement will be completed in a single transaction to ensure ACID properties.
With publish-subscribe messaging many senders can send messages to an entity on the server, often called a topic (e.g. in the JMS world).
There can be many subscriptions on a topic, a subscription is just another word for a consumer of a topic. Each subscription receives a copy of each message sent to the topic. This differs from the message queue pattern where each message is only consumed by a single consumer.
Subscriptions can optionally be durable which means they retain a copy of each message sent to the topic until the subscriber consumes them - even if the server crashes or is restarted in between. Non-durable subscriptions only last a maximum of the lifetime of the connection that created them.
An example of publish-subscribe messaging would be a news feed. As news articles are created by different editors around the world they are sent to a news feed topic. There are many subscribers around the world who are interested in receiving news items - each one creates a subscription and the messaging system ensures that a copy of each news message is delivered to each subscription.
A key feature of most messaging systems is reliable messaging. With reliable messaging the server gives a guarantee that the message will be delivered once and only once to each consumer of a queue or each durable subscription of a topic, even in the event of system failure. This is crucial for many businesses; e.g. you don't want your orders fulfilled more than once or any of your orders to be lost.
In other cases you may not care about a once and only once delivery guarantee and are happy to cope with duplicate deliveries or lost messages - an example of this might be transient stock price updates - which are quickly superseded by the next update on the same stock. The messaging system allows you to configure which delivery guarantees you require.
Messaging systems typically support the sending and acknowledgement of multiple messages in a single local transaction. HornetQ also supports the sending and acknowledgement of message as part of a large global transaction - using the Java mapping of XA; JTA.
Messages are either durable or non durable. Durable messages will be persisted in permanent storage and will survive server failure or restart. Non durable messages will not survive server failure or restart. Examples of durable messages might be orders or trades, where they cannot be lost. An example of a non durable message might be a stock price update which is transitory and doesn't need to survive a restart.
How do client applications interact with messaging systems in order to send and consume messages?
Several messaging systems provide their own proprietary APIs with which the client communicates with the messaging system.
There are also some standard ways of operating with messaging systems and some emerging standards in this space.
Let's take a brief look at these:
JMS is part of Sun's JEE specification. It's a Java API that encapsulates both message queue and publish-subscribe messaging patterns. JMS is a lowest common denominator specification - i.e. it was created to encapsulate common functionality of the already existing messaging systems that were available at the time of its creation.
JMS is a very popular API and is implemented by most, messaging systems. JMS is only available to clients running Java.
JMS does not define a standard wire format - it only defines a programmatic API so JMS clients and servers from different vendors cannot directly interoperate since each will use the vendor's own internal wire protocol.
HornetQ provides a fully compliant JMS 1.1 API.
Many systems provide their own programmatic API for which to interact with the messaging system. The advantage of this it allows the full set of system functionality to be exposed to the client application. API's like JMS are not normally rich enough to expose all the extra features that most messaging systems provide.
HornetQ provides its own core client API for clients to use if they wish to have access to functionality over and above that accessible via the JMS API.
REST approaches to messaging are showing a lot interest recently.
It seems plausible that API standards for cloud computing may converge on a REST style set of interfaces and consequently a REST messaging approach is a very strong contender for becoming the defacto method for messaging interoperability.
With a REST approach messaging resources are manipulated as resources defined by a URI and typically using a simple set of operations on those resources, e.g. PUT, POST, GET etc. REST approaches to messaging often use HTTP as their underlying protocol.
The advantage of a REST approach with HTTP is in its simplicity and the fact the internet is already tuned to deal with HTTP optimally.
Please see Chapter 43, REST Interface for using HornetQ's RESTful interface.
Stomp is a very simple text protocol for interoperating with messaging systems. It defines a wire format, so theoretically any Stomp client can work with any messaging system that supports Stomp. Stomp clients are available in many different programming languages.
Please see Section 47.1, “Stomp” for using STOMP with HornetQ.
AMQP is a specification for interoperable messaging. It also defines a wire format, so any AMQP client can work with any messaging system that supports AMQP. AMQP clients are available in many different programming languages.
HornetQ will shortly be implementing AMQP.
High Availability (HA) means that the system should remain operational after failure of one or more of the servers. The degree of support for HA varies between various messaging systems.
HornetQ provides automatic failover where your sessions are automatically reconnected to the backup server on event of live server failure.
For more information on HA, please see Chapter 39, High Availability and Failover.
Many messaging systems allow you to create groups of messaging servers called clusters. Clusters allow the load of sending and consuming messages to be spread over many servers. This allows your system to scale horizontally by adding new servers to the cluster.
Degrees of support for clusters varies between messaging systems, with some systems having fairly basic clusters with the cluster members being hardly aware of each other.
HornetQ provides very configurable state-of-the-art clustering model where messages can be intelligently load balanced between the servers in the cluster, according to the number of consumers on each node, and whether they are ready for messages.
HornetQ also has the ability to automatically redistribute messages between nodes of a cluster to prevent starvation on any particular node.
For full details on clustering, please see Chapter 38, Clusters.
Some messaging systems allow isolated clusters or single nodes to be bridged together, typically over unreliable connections like a wide area network (WAN), or the internet.
A bridge normally consumes from a queue on one server and forwards messages to another queue on a different server. Bridges cope with unreliable connections, automatically reconnecting when the connections becomes available again.
HornetQ bridges can be configured with filter expressions to only forward certain messages, and transformation can also be hooked in.
HornetQ also allows routing between queues to be configured in server side configuration. This allows complex routing networks to be set up forwarding or copying messages from one destination to another, forming a global network of interconnected brokers.
For more information please see Chapter 36, Core Bridges and Chapter 35, Diverting and Splitting Message Flows.
In this section we will give an overview of the HornetQ high level architecture.
HornetQ core is designed simply as set of Plain Old Java Objects (POJOs) - we hope you like it's clean-cut design.
We've also designed it to have as few dependencies on external jars as possible. In fact, HornetQ core has only one jar dependency, netty.jar, other than the standard JDK classes! This is because we use some of the netty buffer classes internally.
This allows HornetQ to be easily embedded in your own project, or instantiated in any dependency injection framework such as JBoss Microcontainer, Spring or Google Guice.
Each HornetQ server has its own ultra high performance persistent journal, which it uses for message and other persistence.
Using a high performance journal allows outrageous persistence message performance, something not achievable when using a relational database for persistence.
HornetQ clients, potentially on different physical machines interact with the HornetQ server. HornetQ currently provides two APIs for messaging at the client side:
Core client API. This is a simple intuitive Java API that allows the full set of messaging functionality without some of the complexities of JMS.
JMS client API. The standard JMS API is available at the client side.
JMS semantics are implemented by a thin JMS facade layer on the client side.
The HornetQ server does not speak JMS and in fact does not know anything about JMS, it's a protocol agnostic messaging server designed to be used with multiple different protocols.
When a user uses the JMS API on the client side, all JMS interactions are translated into operations on the HornetQ core client API before being transferred over the wire using the HornetQ wire format.
The server always just deals with core API interactions.
A schematic illustrating this relationship is shown in figure 3.1 below:
Figure 3.1 shows two user applications interacting with a HornetQ server. User Application 1 is using the JMS API, while User Application 2 is using the core client API directly.
You can see from the diagram that the JMS API is implemented by a thin facade layer on the client side.
HornetQ core is designed as a set of simple POJOs so if you have an application that requires messaging functionality internally but you don't want to expose that as a HornetQ server you can directly instantiate and embed HornetQ servers in your own application.
For more information on embedding HornetQ, see Chapter 44, Embedding HornetQ.
HornetQ provides its own fully functional Java Connector Architecture (JCA) adaptor which enables it to be integrated easily into any JEE compliant application server or servlet engine.
JEE application servers provide Message Driven Beans (MDBs), which are a special type of Enterprise Java Beans (EJBs) that can process messages from sources such as JMS systems or mail systems.
Probably the most common use of an MDB is to consume messages from a JMS messaging system.
According to the JEE specification, a JEE application server uses a JCA adapter to integrate with a JMS messaging system so it can consume messages for MDBs.
However, the JCA adapter is not only used by the JEE application server for consuming messages via MDBs, it is also used when sending message to the JMS messaging system e.g. from inside an EJB or servlet.
When integrating with a JMS messaging system from inside a JEE application server it is always recommended that this is done via a JCA adaptor. In fact, communicating with a JMS messaging system directly, without using JCA would be illegal according to the JEE specification.
The application server's JCA service provides extra functionality such as connection pooling and automatic transaction enlistment, which are desirable when using messaging, say, from inside an EJB. It is possible to talk to a JMS messaging system directly from an EJB, MDB or servlet without going through a JCA adapter, but this is not recommended since you will not be able to take advantage of the JCA features, such as caching of JMS sessions, which can result in poor performance.
Figure 3.2 below shows a JEE application server integrating with a HornetQ server via the HornetQ JCA adaptor. Note that all communication between EJB sessions or entity beans and Message Driven beans go through the adaptor and not directly to HornetQ.
The large arrow with the prohibited sign shows an EJB session bean talking directly to the HornetQ server. This is not recommended as you'll most likely end up creating a new connection and session every time you want to interact from the EJB, which is an anti-pattern.
For more information on using the JCA adaptor, please see Chapter 32, Application Server Integration and Java EE.
HornetQ can also be deployed as a stand-alone server. This means a fully independent messaging server not dependent on a JEE application server.
The standard stand-alone messaging server configuration comprises a core messaging server, a JMS service and a JNDI service.
The role of the JMS Service is to deploy any JMS Queue, Topic and ConnectionFactory
instances from any server side hornetq-jms.xml
configuration files.
It also provides a simple management API for creating and destroying Queues, Topics and
ConnectionFactory instances which can be accessed via JMX or the connection. It is a
separate service to the HornetQ core server, since the core server is JMS agnostic. If
you don't want to deploy any JMS Queue, Topic or ConnectionFactory instances via server
side XML configuration and don't require a JMS management API on the server side then
you can disable this service.
We also include a JNDI server since JNDI is a common requirement when using JMS to lookup Queues, Topics and ConnectionFactory instances. If you do not require JNDI then this service can also be disabled. HornetQ allows you to programmatically create JMS and core objects directly on the client side as opposed to looking them up from JNDI, so a JNDI server is not always a requirement.
The stand-alone server configuration uses JBoss Microcontainer to instantiate and enforce dependencies between the components. JBoss Microcontainer is a very lightweight POJO bootstrapper.
The stand-alone server architecture is shown in figure 3.3 below:
For more information on server configuration files see Section 49.1, “Server Configuration”. $
This chapter will familiarise you with how to use the HornetQ server.
We'll show where it is, how to start and stop it, and we'll describe the directory layout and what all the files are and what they do.
For the remainder of this chapter when we talk about the HornetQ server we mean the HornetQ standalone server, in its default configuration with a JMS Service and JNDI service enabled.
When running embedded in JBoss Application Server the layout may be slightly different but by-and-large will be the same.
In the distribution you will find a directory called bin
.
cd
into that directory and you'll find a unix/linux script called
run.sh
and a windows batch file called run.bat
To run on Unix/Linux type ./run.sh
To run on Windows type run.bat
These scripts are very simple and basically just set-up the classpath and some JVM parameters and start the JBoss Microcontainer. The Microcontainer is a light weight container used to deploy the HornetQ POJO's
To stop the server you'll also find a unix/linux script stop.sh
and
a windows batch file stop.bat
To run on Unix/Linux type ./stop.sh
To run on Windows type stop.bat
Please note that HornetQ requires a Java 6 or later runtime to run.
Both the run and the stop scripts use the config under config/stand-alone/non-clustered
by default. The configuration can be
changed by running ./run.sh ../config/stand-alone/clustered
or
another config of your choosing. This is the same for the stop script and the windows
bat files.
The run scripts run.sh
and run.bat
set some JVM
settings for tuning running on Java 6 and choosing the garbage collection policy. We
recommend using a parallel garbage collection algorithm to smooth out latency and
minimise large GC pauses.
By default HornetQ runs in a maximum of 1GiB of RAM. To increase the memory settings
change the -Xms
and -Xmx
memory settings as you
would for any Java program.
If you wish to add any more JVM arguments or tune the existing ones, the run scripts are the place to do it.
HornetQ looks for its configuration files on the Java classpath.
The scripts run.sh
and run.bat
specify the
classpath when calling Java to run the server.
In the distribution, the run scripts will add the non clustered configuration
directory to the classpath. This is a directory which contains a set of configuration
files for running the HornetQ server in a basic non-clustered configuration. In the
distribution this directory is config/stand-alone/non-clustered/
from
the root of the distribution.
The distribution contains several standard configuration sets for running:
Non clustered stand-alone.
Clustered stand-alone
Non clustered in JBoss Application Server
Clustered in JBoss Application Server
You can of course create your own configuration and specify any configuration directory when running the run script.
Just make sure the directory is on the classpath and HornetQ will search there when starting up.
If you're using the Asynchronous IO Journal on
Linux, you need to specify java.library.path
as a property on your
Java options. This is done automatically in the run.sh
script.
If you don't specify java.library.path
at your Java options then
the JVM will use the environment variable LD_LIBRARY_PATH
.
HornetQ can take a system property on the command line for configuring logging.
For more information on configuring logging, please see Chapter 42, Logging.
The configuration directory is specified on the classpath in the run scripts run.sh
and run.bat
This directory can contain the
following files.
hornetq-beans.xml
(or hornetq-jboss-beans.xml
if you're running inside JBoss
Application Server). This is the JBoss Microcontainer beans file which defines
what beans the Microcontainer should create and what dependencies to enforce
between them. Remember that HornetQ is just a set of POJOs. In the stand-alone
server, it's the JBoss Microcontainer which instantiates these POJOs and
enforces dependencies between them and other beans.
hornetq-configuration.xml
. This is the main HornetQ
configuration file. All the parameters in this file are described in Chapter 49, Configuration Reference. Please see Section 6.9, “The main configuration file.” for more information on this file.
hornetq-queues.xml
. This file contains predefined queues,
queue settings and security settings. The file is optional - all this
configuration can also live in hornetq-configuration.xml
. In
fact, the default configuration sets do not have a hornetq-queues.xml
file. The purpose of allowing queues to be
configured in these files is to allow you to manage your queue configuration
over many files instead of being forced to maintain it in a single file. There
can be many hornetq-queues.xml
files on the classpath. All
will be loaded if found.
hornetq-users.xml
HornetQ ships with a basic security
manager implementation which obtains user credentials from the hornetq-users.xml
file. This file contains user, password and
role information. For more information on security, please see Chapter 31, Security.
hornetq-jms.xml
The distro configuration by default
includes a server side JMS service which mainly deploys JMS Queues, Topics and
ConnectionFactorys from this file into JNDI. If you're not using JMS, or you
don't need to deploy JMS objects on the server side, then you don't need this
file. For more information on using JMS, please see Chapter 7, Using JMS.
logging.properties
This is used to configure the logging
handlers used by the Java logger. For more information on configuring logging,
please see Chapter 42, Logging.
log4j.xml
This is the Log4j configuration if the Log4j
handler is configured.
The property file-deployment-enabled
in the hornetq-configuration.xml
configuration when set to false means that
the other configuration files are not loaded. This is true by default.
It is also possible to use system property substitution in all the configuration files. by replacing a value with the name of a system property. Here is an example of this with a connector configuration:
<connector name="netty"> <factory-class>org.hornetq.core.remoting.impl.netty.NettyConnectorFactory</factory-class> <param key="host" value="${hornetq.remoting.netty.host:localhost}" type="String"/> <param key="port" value="${hornetq.remoting.netty.port:5445}" type="Integer"/> </connector>
Here you can see we have replaced 2 values with system properties hornetq.remoting.netty.host
and hornetq.remoting.netty.port
. These values will be replaced by the value
found in the system property if there is one, if not they default back to localhost or
5445 respectively. It is also possible to not supply a default. i.e. ${hornetq.remoting.netty.host}
, however the system property
must be supplied in that case.
The stand-alone server is basically a set of POJOs which are instantiated by the light weight JBoss Microcontainer engine.
A beans file is also needed when the server is deployed in the JBoss Application Server but this will deploy a slightly different set of objects since the Application Server will already have things like security etc deployed.
Let's take a look at an example beans file from the stand-alone server:
<?xml version="1.0" encoding="UTF-8"?> <deployment xmlns="urn:jboss:bean-deployer:2.0"> <bean name="Naming" class="org.jnp.server.NamingBeanImpl"/> <!-- JNDI server. Disable this if you don't want JNDI --> <bean name="JNDIServer" class="org.jnp.server.Main"> <property name="namingInfo"> <inject bean="Naming"/> </property> <property name="port">1099</property> <property name="bindAddress">localhost</property> <property name="rmiPort">1098</property> <property name="rmiBindAddress">localhost</property> </bean> <!-- MBean server --> <bean name="MBeanServer" class="javax.management.MBeanServer"> <constructor factoryClass="java.lang.management.ManagementFactory" factoryMethod="getPlatformMBeanServer"/> </bean> <!-- The core configuration --> <bean name="Configuration" class="org.hornetq.core.config.impl.FileConfiguration"> </bean> <!-- The security manager --> <bean name="HornetQSecurityManager" class="org.hornetq.spi.core.security.HornetQSecurityManagerImpl"> <start ignored="true"/> <stop ignored="true"/> </bean> <!-- The core server --> <bean name="HornetQServer" class="org.hornetq.core.server.impl.HornetQServerImpl"> <start ignored="true"/> <stop ignored="true"/> <constructor> <parameter> <inject bean="Configuration"/> </parameter> <parameter> <inject bean="MBeanServer"/> </parameter> <parameter> <inject bean="HornetQSecurityManager"/> </parameter> </constructor> </bean> <!-- The JMS server --> <bean name="JMSServerManager" class="org.hornetq.jms.server.impl.JMSServerManagerImpl"> <constructor> <parameter> <inject bean="HornetQServer"/> </parameter> </constructor> </bean> </deployment>
We can see that, as well as the core HornetQ server, the stand-alone server instantiates various different POJOs, lets look at them in turn:
JNDIServer
Many clients like to look up JMS Objects from JNDI so we provide a JNDI server for them to do that. If you don't need JNDI this can be commented out or removed.
MBeanServer
In order to provide a JMX management interface a JMS MBean server is necessary in which to register the management objects. Normally this is just the default platform MBean server available in the JVM instance. If you don't want to provide a JMX management interface this can be commented out or removed.
Configuration
The HornetQ server is configured with a Configuration object. In the default stand-alone set-up it uses a FileConfiguration object which knows to read configuration information from the file system. In different configurations such as embedded you might want to provide configuration information from somewhere else.
Security Manager. The security manager used by the messaging server is
pluggable. The default one used just reads user-role information from the
hornetq-users.xml
file on disk. However it can be
replaced by a JAAS security manager, or when running inside JBoss Application
Server it can be configured to use the JBoss AS security manager for tight
integration with JBoss AS security. If you've disabled security altogether you
can remove this too.
HornetQServer
This is the core server. It's where 99% of the magic happens
This deploys any JMS Objects such as JMS Queues, Topics and ConnectionFactory
instances from hornetq-jms.xml
files on the disk. It also
provides a simple management API for manipulating JMS Objects. On the whole it
just translates and delegates its work to the core server. If you don't need to
deploy JMS Queues, Topics and ConnectionFactorys from server side configuration
and don't require the JMS management interface this can be disabled.
The section is only to configure HornetQ on JBoss AS4. The service funtionality is similar to Microcontainer Beans
<?xml version="1.0" encoding="UTF-8"?> <server> <mbean code="org.hornetq.service.HornetQFileConfigurationService" name="org.hornetq:service=HornetQFileConfigurationService"> </mbean> <mbean code="org.hornetq.service.JBossASSecurityManagerService" name="org.hornetq:service=JBossASSecurityManagerService"> </mbean> <mbean code="org.hornetq.service.HornetQStarterService" name="org.hornetq:service=HornetQStarterService"> <!--lets let the JMS Server start us--> <attribute name="Start">false</attribute> <depends optional-attribute-name="SecurityManagerService" proxy-type="attribute">org.hornetq:service=JBossASSecurityManagerService</depends> <depends optional-attribute-name="ConfigurationService" proxy-type="attribute">org.hornetq:service=HornetQFileConfigurationService</depends> </mbean> <mbean code="org.hornetq.service.HornetQJMSStarterService" name="org.hornetq:service=HornetQJMSStarterService"> <depends optional-attribute-name="HornetQServer" proxy-type="attribute">org.hornetq:service=HornetQStarterService</depends> </mbean> </server>
This jboss-service.xml configuration file is included inside the hornetq-service.sar on AS4 with embebbed HornetQ. As you can see, on this configuration file we are starting various services:
HornetQFileConfigurationService
This is an MBean Service that takes care of the life cycle of the FileConfiguration POJO
JBossASSecurityManagerService
This is an MBean Service that takes care of the lifecycle of the JBossASSecurityManager
POJO
HornetQStarterService
This is an MBean Service that controls the main HornetQServer
POJO.
this has a dependency on JBossASSecurityManagerService and HornetQFileConfigurationService MBeans
HornetQJMSStarterService
This is an MBean Service that controls the JMSServerManagerImpl
POJO.
If you aren't using jms this can be removed.
JMSServerManager
Has the responsibility to start the JMSServerManager and the same behaviour that JMSServerManager Bean
The configuration for the HornetQ core server is contained in hornetq-configuration.xml
. This is what the FileConfiguration bean uses
to configure the messaging server.
There are many attributes which you can configure HornetQ. In most cases the defaults
will do fine, in fact every attribute can be defaulted which means a file with a single
empty configuration
element is a valid configuration file. The
different configuration will be explained throughout the manual or you can refer to the
configuration reference here.
Although HornetQ provides a JMS agnostic messaging API, many users will be more comfortable using JMS.
JMS is a very popular API standard for messaging, and most messaging systems provide a JMS API. If you are completely new to JMS we suggest you follow the Sun JMS tutorial - a full JMS tutorial is out of scope for this guide.
HornetQ also ships with a wide range of examples, many of which demonstrate JMS API usage. A good place to start would be to play around with the simple JMS Queue and Topic example, but we also provide examples for many other parts of the JMS API. A full description of the examples is available in Chapter 11, Examples.
In this section we'll go through the main steps in configuring the server for JMS and creating a simple JMS program. We'll also show how to configure and use JNDI, and also how to use JMS with HornetQ without using any JNDI.
For this chapter we're going to use a very simple ordering system as our example. It's a somewhat contrived example because of its extreme simplicity, but it serves to demonstrate the very basics of setting up and using JMS.
We will have a single JMS Queue called OrderQueue
, and we will have
a single MessageProducer
sending an order message to the queue and a
single MessageConsumer
consuming the order message from the
queue.
The queue will be a durable
queue, i.e. it will survive a server
restart or crash. We also want to predeploy the queue, i.e. specify the queue in the
server JMS configuration so it's created automatically without us having to explicitly
create it from the client.
The file hornetq-jms.xml
on the server classpath contains any JMS
Queue, Topic and ConnectionFactory instances that we wish to create and make available
to lookup via the JNDI.
A JMS ConnectionFactory object is used by the client to make connections to the server. It knows the location of the server it is connecting to, as well as many other configuration parameters. In most cases the defaults will be acceptable.
We'll deploy a single JMS Queue and a single JMS Connection Factory instance on the server for this example but there are no limits to the number of Queues, Topics and Connection Factory instances you can deploy from the file. Here's our configuration:
<configuration xmlns="urn:hornetq" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="urn:hornetq ../schemas/hornetq-jms.xsd "> <connection-factory name="ConnectionFactory"> <connectors> <connector-ref connector-name="netty"/> </connectors> <entries> <entry name="ConnectionFactory"/> </entries> </connection-factory> <queue name="OrderQueue"> <entry name="queues/OrderQueue"/> </queue> </configuration>
We deploy one ConnectionFactory called ConnectionFactory
and bind
it in just one place in JNDI as given by the entry
element.
ConnectionFactory instances can be bound in many places in JNDI if you require.
The JMS connection factory references a connector
called
netty
. This is a reference to a connector object deployed in
the main core configuration file hornetq-configuration.xml
which
defines the transport and parameters used to actually connect to the server.
The JMS API doc provides several connection factories for applications. HornetQ JMS users
can choose to configure the types for their connection factories. Each connection factory
has a signature
attribute and a xa
parameter, the
combination of which determines the type of the factory. Attribute signature
has three possible string values, i.e. generic,
queue and topic; xa
is a boolean
type parameter. The following table gives their configuration values for different
connection factory interfaces.
Table 7.1. Configuration for Connection Factory Types
signature | xa | Connection Factory Type |
---|---|---|
generic (default) | false (default) | javax.jms.ConnectionFactory |
generic | true | javax.jms.XAConnectionFactory |
queue | false | javax.jms.QueueConnectionFactory |
queue | true | javax.jms.XAQueueConnectionFactory |
topic | false | javax.jms.TopicConnectionFactory |
topic | true | javax.jms.XATopicConnectionFactory |
As an example, the following configures an XAQueueConnectionFactory:
<configuration xmlns="urn:hornetq" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="urn:hornetq ../schemas/hornetq-jms.xsd "> <connection-factory name="ConnectionFactory" signature="queue"> <xa>true</xa> <connectors> <connector-ref connector-name="netty"/> </connectors> <entries> <entry name="ConnectionFactory"/> </entries> </connection-factory> </configuration>
When using JNDI from the client side you need to specify a set of JNDI properties
which tell the JNDI client where to locate the JNDI server, amongst other things. These
are often specified in a file called jndi.properties
on the client
classpath, or you can specify them directly when creating the JNDI initial context. A
full JNDI tutorial is outside the scope of this document, please see the Sun JNDI tutorial
for more information on how to use JNDI.
For talking to the JBoss JNDI Server, the jndi properties will look something like this:
java.naming.factory.initial=org.jnp.interfaces.NamingContextFactory java.naming.provider.url=jnp://myhost:1099 java.naming.factory.url.pkgs=org.jboss.naming:org.jnp.interfaces
Where myhost
is the hostname or IP address of the JNDI server. 1099
is the port used by the JNDI server and may vary depending on how you have configured
your JNDI server.
In the default standalone configuration, JNDI server ports are configured in the file
hornetq-beans.xml
by setting properties on the JNDIServer
bean:
<bean name="JNDIServer" class="org.jnp.server.Main"> <property name="namingInfo"> <inject bean="Naming"/> </property> <property name="port">1099</property> <property name="bindAddress">localhost</property> <property name="rmiPort">1098</property> <property name="rmiBindAddress">localhost</property> </bean>
If you want your JNDI server to be available to non local clients make sure you
change it's bind address to something other than localhost
!
The JNDIServer bean must be defined only when HornetQ is running in stand-alone mode. When HornetQ is integrated to JBoss Application Server, JBoss AS will provide a ready-to-use JNDI server without any additional configuration.
Here's the code for the example:
First we'll create a JNDI initial context from which to lookup our JMS objects:
InitialContect ic = new InitialContext();
Now we'll look up the connection factory:
ConnectionFactory cf = (ConnectionFactory)ic.lookup("/ConnectionFactory");
And look up the Queue:
Queue orderQueue = (Queue)ic.lookup("/queues/OrderQueue");
Next we create a JMS connection using the connection factory:
Connection connection = cf.createConnection();
And we create a non transacted JMS Session, with AUTO_ACKNOWLEDGE acknowledge mode:
Session session = connection.createSession(false, Session.AUTO_ACKNOWLEDGE);
We create a MessageProducer that will send orders to the queue:
MessageProducer producer = session.createProducer(orderQueue);
And we create a MessageConsumer which will consume orders from the queue:
MessageConsumer consumer = session.createConsumer(orderQueue);
We make sure we start the connection, or delivery won't occur on it:
connection.start();
We create a simple TextMessage and send it:
TextMessage message = session.createTextMessage("This is an order"); producer.send(message);
And we consume the message:
TextMessage receivedMessage = (TextMessage)consumer.receive(); System.out.println("Got order: " + receivedMessage.getText());
It's as simple as that. For a wide range of working JMS examples please see the examples directory in the distribution.
Please note that JMS connections, sessions, producers and consumers are designed to be re-used.
It's an anti-pattern to create new connections, sessions, producers and consumers for each message you produce or consume. If you do this, your application will perform very poorly. This is discussed further in the section on performance tuning Chapter 48, Performance Tuning.
Although it's a very common JMS usage pattern to lookup JMS Administered Objects (that's JMS Queue, Topic and ConnectionFactory instances) from JNDI, in some cases a JNDI server is not available and you still want to use JMS, or you just think "Why do I need JNDI? Why can't I just instantiate these objects directly?"
With HornetQ you can do exactly that. HornetQ supports the direct instantiation of JMS Queue, Topic and ConnectionFactory instances, so you don't have to use JNDI at all.
For a full working example of direct instantiation please see the JMS examples in Chapter 11, Examples.
Here's our simple example, rewritten to not use JNDI at all:
We create the JMS ConnectionFactory object via the HornetQJMSClient Utility class, note we need to provide connection parameters and specify which transport we are using, for more information on connectors please see Chapter 16, Configuring the Transport.
TransportConfiguration transportConfiguration = new TransportConfiguration(NettyConnectorFactory.class.getName()); ConnectionFactory cf = HornetQJMSClient.createConnectionFactoryWithoutHA(JMSFactoryType.CF,transportConfiguration);
We also create the JMS Queue object via the HornetQJMSClient Utility class:
Queue orderQueue = HornetQJMSClient.createQueue("OrderQueue");
Next we create a JMS connection using the connection factory:
Connection connection = cf.createConnection();
And we create a non transacted JMS Session, with AUTO_ACKNOWLEDGE acknowledge mode:
Session session = connection.createSession(false, Session.AUTO_ACKNOWLEDGE);
We create a MessageProducer that will send orders to the queue:
MessageProducer producer = session.createProducer(orderQueue);
And we create a MessageConsumer which will consume orders from the queue:
MessageConsumer consumer = session.createConsumer(orderQueue);
We make sure we start the connection, or delivery won't occur on it:
connection.start();
We create a simple TextMessage and send it:
TextMessage message = session.createTextMessage("This is an order"); producer.send(message);
And we consume the message:
TextMessage receivedMessage = (TextMessage)consumer.receive(); System.out.println("Got order: " + receivedMessage.getText());
This represents the client id for a JMS client and is needed for creating durable
subscriptions. It is possible to configure this on the connection factory and can be set
via the client-id
element. Any connection created by this connection
factory will have this set as its client id.
When the JMS acknowledge mode is set to DUPS_OK
it is possible to
configure the consumer so that it sends acknowledgements in batches rather that one at a
time, saving valuable bandwidth. This can be configured via the connection factory via
the dups-ok-batch-size
element and is set in bytes. The default is
1024 * 1024 bytes = 1 MiB.
When receiving messages in a transaction it is possible to configure the consumer to
send acknowledgements in batches rather than individually saving valuable bandwidth.
This can be configured on the connection factory via the transaction-batch-size
element and is set in bytes. The default is 1024 *
1024.
HornetQ core is a completely JMS-agnostic messaging system with its own non-JMS API. We call this the core API.
If you don't want to use JMS you can use the core API directly. The core API provides all the functionality of JMS but without much of the complexity. It also provides features that are not available using JMS.
Some of the core messaging concepts are similar to JMS concepts, but core messaging concepts differ in some ways. In general the core messaging API is simpler than the JMS API, since we remove distinctions between queues, topics and subscriptions. We'll discuss each of the major core messaging concepts in turn, but to see the API in detail, please consult the Javadoc.
A message is the unit of data which is sent between clients and servers.
A message has a body which is a buffer containing convenient methods for reading and writing data into it.
A message has a set of properties which are key-value pairs. Each property key is a string and property values can be of type integer, long, short, byte, byte[], String, double, float or boolean.
A message has an address it is being sent to. When the message arrives on the server it is routed to any queues that are bound to the address - if the queues are bound with any filter, the message will only be routed to that queue if the filter matches. An address may have many queues bound to it or even none. There may also be entities other than queues, like diverts bound to addresses.
Messages can be either durable or non durable. Durable messages in a durable queue will survive a server crash or restart. Non durable messages will never survive a server crash or restart.
Messages can be specified with a priority value between 0 and 9. 0 represents the lowest priority and 9 represents the highest. HornetQ will attempt to deliver higher priority messages before lower priority ones.
Messages can be specified with an optional expiry time. HornetQ will not deliver messages after its expiry time has been exceeded.
Messages also have an optional timestamp which represents the time the message was sent.
HornetQ also supports the sending/consuming of very large messages - much larger than can fit in available RAM at any one time.
A server maintains a mapping between an address and a set of queues. Zero or more queues can be bound to a single address. Each queue can be bound with an optional message filter. When a message is routed, it is routed to the set of queues bound to the message's address. If any of the queues are bound with a filter expression, then the message will only be routed to the subset of bound queues which match that filter expression.
Other entities, such as diverts can also be bound to an address and messages will also be routed there.
In core, there is no concept of a Topic, Topic is a JMS only term. Instead, in core, we just deal with addresses and queues.
For example, a JMS topic would be implemented by a single address to which many queues are bound. Each queue represents a subscription of the topic. A JMS Queue would be implemented as a single address to which one queue is bound - that queue represents the JMS queue.
Queues can be durable, meaning the messages they contain survive a server crash or restart, as long as the messages in them are durable. Non durable queues do not survive a server restart or crash even if the messages they contain are durable.
Queues can also be temporary, meaning they are automatically deleted when the client connection is closed, if they are not explicitly deleted before that.
Queues can be bound with an optional filter expression. If a filter expression is supplied then the server will only route messages that match that filter expression to any queues bound to the address.
Many queues can be bound to a single address. A particular queue is only bound to a maximum of one address.
Clients use ServerLocator
instances to create ClientSessionFactory
instances. ServerLocator
instances are used to locate servers and create connections to them.
In JMS terms think of a ServerLocator
in the same way you would
a JMS Connection Factory
ServerLocator
instances are created using the HornetQClient
factory class.
Clients use ClientSessionFactory
instances to create ClientSession
instances. ClientSessionFactory
instances are basically the connection to a server
In JMS terms think of them as JMS Connections
ClientSessionFactory
instances are created using the ServerLocator
class.
A client uses a ClientSession for consuming and producing messages and for
grouping them in transactions. ClientSession instances can support both
transactional and non transactional semantics and also provide an XAResource
interface so messaging operations can be performed as part
of a JTA
transaction.
ClientSession instances group ClientConsumers and ClientProducers.
ClientSession instances can be registered with an optional SendAcknowledgementHandler
. This allows your client code to be
notified asynchronously when sent messages have successfully reached the server.
This unique HornetQ feature, allows you to have full guarantees that sent messages
have reached the server without having to block on each message sent until a
response is received. Blocking on each messages sent is costly since it requires a
network round trip for each message sent. By not blocking and receiving send
acknowledgements asynchronously you can create true end to end asynchronous systems
which is not possible using the standard JMS API. For more information on this
advanced feature please see the section Chapter 20, Guarantees of sends and commits.
Clients use ClientConsumer
instances to consume messages from a
queue. Core Messaging supports both synchronous and asynchronous message consumption
semantics. ClientConsumer
instances can be configured with an
optional filter expression and will only consume messages which match that
expression.
Clients create ClientProducer
instances on ClientSession
instances so they can send messages. ClientProducer
instances can specify an address to which all sent messages are routed, or they can
have no specified address, and the address is specified at send time for the
message.
Please note that ClientSession, ClientProducer and ClientConsumer instances are designed to be re-used.
It's an anti-pattern to create new ClientSession, ClientProducer and ClientConsumer instances for each message you produce or consume. If you do this, your application will perform very poorly. This is discussed further in the section on performance tuning Chapter 48, Performance Tuning.
Here's a very simple program using the core messaging API to send and receive a message:
ServerLocator locator = HornetQClient.createServerLocatorWithoutHA(new TransportConfiguration( InVMConnectorFactory.class.getName())); ClientSessionFactory factory = locator.createClientSessionFactory(); ClientSession session = factory.createSession(); session.createQueue("example", "example", true); ClientProducer producer = session.createProducer("example"); ClientMessage message = session.createMessage(true); message.getBodyBuffer().writeString("Hello"); producer.send(message); session.start(); ClientConsumer consumer = session.createConsumer("example"); ClientMessage msgReceived = consumer.receive(); System.out.println("message = " + msgReceived.getBodyBuffer().readString()); session.close();
This chapter describes how JMS destinations are mapped to HornetQ addresses.
HornetQ core is JMS-agnostic. It does not have any concept of a JMS topic. A JMS topic is implemented in core as an address (the topic name) with zero or more queues bound to it. Each queue bound to that address represents a topic subscription. Likewise, a JMS queue is implemented as an address (the JMS queue name) with one single queue bound to it which represents the JMS queue.
By convention, all JMS queues map to core queues where the core queue name has the string
jms.queue.
prepended to it. E.g. the JMS queue with the name
"orders.europe" would map to the core queue with the name "jms.queue.orders.europe". The
address at which the core queue is bound is also given by the core queue name.
For JMS topics the address at which the queues that represent the subscriptions are bound is given by prepending the string "jms.topic." to the name of the JMS topic. E.g. the JMS topic with name "news.europe" would map to the core address "jms.topic.news.europe"
In other words if you send a JMS message to a JMS queue with name "orders.europe" it will get routed on the server to any core queues bound to the address "jms.queue.orders.europe". If you send a JMS message to a JMS topic with name "news.europe" it will get routed on the server to any core queues bound to the address "jms.topic.news.europe".
If you want to configure settings for a JMS Queue with the name "orders.europe", you need to configure the corresponding core queue "jms.queue.orders.europe":
<!-- expired messages in JMS Queue "orders.europe" will be sent to the JMS Queue "expiry.europe" --> <address-setting match="jms.queue.orders.europe"> <expiry-address>jms.queue.expiry.europe</expiry-address> ... </address-setting>
HornetQ requires several jars on the Client Classpath depending on whether the client uses HornetQ Core API, JMS, and JNDI.
All the jars mentioned here can be found in the lib
directory of
the HornetQ distribution. Be sure you only use the jars from the correct version of the
release, you must not mix and match versions of jars from different
HornetQ versions. Mixing and matching different jar versions may cause subtle errors and
failures to occur.
If you are using just a pure HornetQ Core client (i.e. no JMS) then you need hornetq-core-client.jar
and
netty.jar
on your client classpath.
If the client runs inside a Java 5 virtual machine, use instead hornetq-core-client-java5.jar
.
If you are using JMS on the client side, then you will also need to include hornetq-jms-client.jar
and jboss-jms-api.jar
.
If the client runs inside a Java 5 virtual machine, include instead hornetq-jms-client-java5.jar
.
jboss-jms-api.jar
just contains Java EE API interface classes
needed for the javax.jms.*
classes. If you already have a jar
with these interface classes on your classpath, you will not need it.
The HornetQ distribution comes with over 70 run out-of-the-box examples demonstrating many of the features.
The examples are available in the distribution, in the examples
directory. Examples are split into JMS and core examples. JMS examples show how a particular
feature can be used by a normal JMS client. Core examples show how the equivalent feature
can be used by a core messaging client.
A set of Java EE examples are also provided which need the JBoss Application Server installed to be able to run.
To run a JMS example, simply cd
into the appropriate example
directory and type ./build.sh
(or build.bat
if you
are on Windows).
Here's a listing of the examples with a brief description.
HornetQ also supports Application-Layer failover, useful in the case that replication is not enabled on the server side.
With Application-Layer failover, it's up to the application to register a JMS
ExceptionListener
with HornetQ which will be called by
HornetQ in the event that connection failure is detected.
The code in the ExceptionListener
then recreates the JMS
connection, session, etc on another node and the application can continue.
Application-layer failover is an alternative approach to High Availability (HA). Application-layer failover differs from automatic failover in that some client side coding is required in order to implement this. Also, with Application-layer failover, since the old session object dies and a new one is created, any uncommitted work in the old session will be lost, and any unacknowledged messages might be redelivered.
The bridge
example demonstrates a core bridge deployed on one
server, which consumes messages from a local queue and forwards them to an address
on a second server.
Core bridges are used to create message flows between any two HornetQ servers which are remotely separated. Core bridges are resilient and will cope with temporary connection failure allowing them to be an ideal choice for forwarding over unreliable connections, e.g. a WAN.
The browser
example shows you how to use a JMS QueueBrowser
with HornetQ.
Queues are a standard part of JMS, please consult the JMS 1.1 specification for full details.
A QueueBrowser
is used to look at messages on the queue
without removing them. It can scan the entire content of a queue or only messages
matching a message selector.
The client-kickoff
example shows how to terminate client
connections given an IP address using the JMX management API.
The client-side-load-balancing
example demonstrates how
sessions created from a single JMS Connection
can
be created to different nodes of the cluster. In other words it demonstrates how
HornetQ does client-side load-balancing of sessions across the cluster.
This example demonstrates a clustered JMS durable subscription
This is similar to the message grouping example except that it demonstrates it working over a cluster. Messages sent to different nodes with the same group id will be sent to the same node and the same consumer.
The clustered-queue
example demonstrates a JMS queue deployed
on two different nodes. The two nodes are configured to form a cluster. We then
create a consumer for the queue on each node, and we create a producer on only one
of the nodes. We then send some messages via the producer, and we verify that both
consumers receive the sent messages in a round-robin fashion.
The clustered-jgroups
example demonstrates how to form a two
node cluster using JGroups as its underlying topology discovery technique, rather than
the default UDP broadcasting. We then create a consumer for the queue on each node,
and we create a producer on only one of the nodes. We then send some messages via the
producer, and we verify that both consumers receive the sent messages in a round-robin fashion.
The clustered-standalone
example demonstrates how to configure
and starts 3 cluster nodes on the same machine to form a cluster. A subscriber for a
JMS topic is created on each node, and we create a producer on only one of the
nodes. We then send some messages via the producer, and we verify that the 3
subscribers receive all the sent messages.
This example demonstrates how to configure a cluster using a list of connectors rather than UDP for discovery
This example demonstrates how to set up a cluster where cluster connections are one way, i.e. server A -> Server B -> Server C
The clustered-topic
example demonstrates a JMS topic deployed
on two different nodes. The two nodes are configured to form a cluster. We then
create a subscriber on the topic on each node, and we create a producer on only one
of the nodes. We then send some messages via the producer, and we verify that both
subscribers receive all the sent messages.
With HornetQ you can specify a maximum consume rate at which a JMS MessageConsumer will consume messages. This can be specified when creating or deploying the connection factory.
If this value is specified then HornetQ will ensure that messages are never consumed at a rate higher than the specified rate. This is a form of consumer throttling.
The dead-letter
example shows you how to define and deal with
dead letter messages. Messages can be delivered unsuccessfully (e.g. if the
transacted session used to consume them is rolled back).
Such a message goes back to the JMS destination ready to be redelivered. However, this means it is possible for a message to be delivered again and again without any success and remain in the destination, clogging the system.
To prevent this, messaging systems define dead letter messages: after a specified unsuccessful delivery attempts, the message is removed from the destination and put instead in a dead letter destination where they can be consumed for further investigation.
The delayed-redelivery
example demonstrates how HornetQ can be
configured to provide a delayed redelivery in the case a message needs to be
redelivered.
Delaying redelivery can often be useful in the case that clients regularly fail or roll-back. Without a delayed redelivery, the system can get into a "thrashing" state, with delivery being attempted, the client rolling back, and delivery being re-attempted in quick succession, using up valuable CPU and network resources.
HornetQ diverts allow messages to be transparently "diverted" or copied from one address to another with just some simple configuration defined on the server side.
The durable-subscription
example shows you how to use a durable
subscription with HornetQ. Durable subscriptions are a standard part of JMS, please
consult the JMS 1.1 specification for full details.
Unlike non-durable subscriptions, the key function of durable subscriptions is that the messages contained in them persist longer than the lifetime of the subscriber - i.e. they will accumulate messages sent to the topic even if there is no active subscriber on them. They will also survive server restarts or crashes. Note that for the messages to be persisted, the messages sent to them must be marked as durable messages.
The embedded
example shows how to embed JMS
within your own code using POJO instantiation and no config files.
The embedded
example shows how to embed JMS within your own code using regular HornetQ XML files.
The expiry
example shows you how to define and deal with
message expiration. Messages can be retained in the messaging system for a limited
period of time before being removed. JMS specification states that clients should
not receive messages that have been expired (but it does not guarantee this will not
happen).
HornetQ can assign an expiry address to a given queue so that when messages are expired, they are removed from the queue and sent to the expiry address. These "expired" messages can later be consumed from the expiry address for further inspection.
The http-transport
example shows you how to configure HornetQ
to use the HTTP protocol as its transport layer.
Usually, JMS Objects such as ConnectionFactory
, Queue
and Topic
instances are looked up from JNDI
before being used by the client code. This objects are called "administered objects"
in JMS terminology.
However, in some cases a JNDI server may not be available or desired. To come to the rescue HornetQ also supports the direct instantiation of these administered objects on the client side so you don't have to use JNDI for JMS.
HornetQ allows an application to use an interceptor to hook into the messaging system. Interceptors allow you to handle various message events in HornetQ.
The jaas
example shows you how to configure HornetQ to use JAAS
for security. HornetQ can leverage JAAS to delegate user authentication and
authorization to existing security infrastructure.
The jms-brige
example shows how to setup a bridge
between two standalone HornetQ servers.
The large-message
example shows you how to send and receive
very large messages with HornetQ. HornetQ supports the sending and receiving of huge
messages, much larger than can fit in available RAM on the client or server.
Effectively the only limit to message size is the amount of disk space you have on
the server.
Large messages are persisted on the server so they can survive a server restart. In other words HornetQ doesn't just do a simple socket stream from the sender to the consumer.
The last-value-queue
example shows you how to define and deal
with last-value queues. Last-value queues are special queues which discard any
messages when a newer message with the same value for a well-defined last-value
property is put in the queue. In other words, a last-value queue only retains the
last value.
A typical example for last-value queue is for stock prices, where you are only interested by the latest price for a particular stock.
The management
example shows how to manage HornetQ using JMS
Messages to invoke management operations on the server.
The management-notification
example shows how to receive
management notifications from HornetQ using JMS messages. HornetQ servers emit
management notifications when events of interest occur (consumers are created or
closed, addresses are created or deleted, security authentication fails,
etc.).
The message-counters
example shows you how to use message
counters to obtain message information for a JMS queue.
The message-group
example shows you how to configure and use
message groups with HornetQ. Message groups allow you to pin messages so they are
only consumed by a single consumer. Message groups are sets of messages that has the
following characteristics:
Messages in a message group share the same group id, i.e. they have same JMSXGroupID string property values
The consumer that receives the first message of a group will receive all the messages that belongs to the group
The message-group2
example shows you how to configure and use
message groups with HornetQ via a connection factory.
Message Priority can be used to influence the delivery order for messages.
It can be retrieved by the message's standard header field 'JMSPriority' as defined in JMS specification version 1.1.
The value is of type integer, ranging from 0 (the lowest) to 9 (the highest). When messages are being delivered, their priorities will effect their order of delivery. Messages of higher priorities will likely be delivered before those of lower priorities.
Messages of equal priorities are delivered in the natural order of their arrival at their destinations. Please consult the JMS 1.1 specification for full details.
This example demonstrates how to set up a live server with multiple backups
This example demonstrates how to set up a live server with multiple backups but forcing failover back to the original live server
By default, HornetQ consumers buffer messages from the server in a client side
buffer before you actually receive them on the client side. This improves
performance since otherwise every time you called receive() or had processed the
last message in a MessageListener onMessage()
method, the HornetQ
client would have to go the server to request the next message, which would then get
sent to the client side, if one was available.
This would involve a network round trip for every message and reduce performance. Therefore, by default, HornetQ pre-fetches messages into a buffer on each consumer.
In some case buffering is not desirable, and HornetQ allows it to be switched off. This example demonstrates that.
The non-transaction-failover
example demonstrates two servers coupled
as a live-backup pair for high availability (HA), and a client using a non-transacted
JMS session failing over from live to backup when the live server is
crashed.
HornetQ implements failover of client connections between live and backup servers. This is implemented by the replication of state between live and backup nodes. When replication is configured and a live node crashes, the client connections can carry and continue to send and consume messages. When non-transacted sessions are used, once and only once message delivery is not guaranteed and it is possible that some messages will be lost or delivered twice.
The paging
example shows how HornetQ can support huge queues
even when the server is running in limited RAM. It does this by transparently
paging messages to disk, and depaging
them when they are required.
Standard JMS supports three acknowledgement modes:
AUTO_ACKNOWLEDGE
, CLIENT_ACKNOWLEDGE
, and DUPS_OK_ACKNOWLEDGE
. For a full description on these modes please
consult the JMS specification, or any JMS tutorial.
All of these standard modes involve sending acknowledgements from the client to the server. However in some cases, you really don't mind losing messages in event of failure, so it would make sense to acknowledge the message on the server before delivering it to the client. This example demonstrates how HornetQ allows this with an extra acknowledgement mode.
The producer-rte-limit
example demonstrates how, with HornetQ,
you can specify a maximum send rate at which a JMS message producer will send
messages.
The queue-message-redistribution
example demonstrates message
redistribution between queues with the same name deployed in different nodes of a
cluster.
The queue-selector
example shows you how to selectively consume
messages using message selectors with queue consumers.
The Reattach Node
example shows how a client can try to reconnect to
the same server instead of failing the connection immediately and
notifying any user ExceptionListener objects. HornetQ can be configured to automatically
retry the connection, and reattach to the server when it becomes available again across
the network.
The scheduled-message
example shows you how to send a scheduled
message to a JMS Queue with HornetQ. Scheduled messages won't get delivered until a
specified time in the future.
The security
example shows you how configure and use role based
queue security with HornetQ.
The send-acknowledgements
example shows you how to use
HornetQ's advanced asynchronous send acknowledgements feature
to obtain acknowledgement from the server that sends have been received and
processed in a separate stream to the sent messages.
This example shows how to use embedded JMS using HornetQ's Spring integration.
The ssl-enabled
shows you how to configure SSL with HornetQ to
send and receive message.
The static-selector
example shows you how to configure a
HornetQ core queue with static message selectors (filters).
The static-selector-jms
example shows you how to configure a
HornetQ queue with static message selectors (filters) using JMS.
The stomp
example shows you how to configure a
HornetQ server to send and receive Stomp messages.
The stomp
example shows you how to configure a
HornetQ server to send and receive Stomp messages via a Stomp 1.1 connection.
The stomp-websockets
example shows you how to configure a
HornetQ server to send and receive Stomp messages directly from Web browsers (provided
they support Web Sockets).
The symmetric-cluster
example demonstrates a symmetric cluster
set-up with HornetQ.
HornetQ has extremely flexible clustering which allows you to set-up servers in many different topologies. The most common topology that you'll perhaps be familiar with if you are used to application server clustering is a symmetric cluster.
With a symmetric cluster, the cluster is homogeneous, i.e. each node is configured the same as every other node, and every node is connected to every other node in the cluster.
HornetQ supports topic hierarchies. With a topic hierarchy you can register a subscriber with a wild-card and that subscriber will receive any messages sent to an address that matches the wild card.
The topic-selector-example1
example shows you how to send
message to a JMS Topic, and subscribe them using selectors with HornetQ.
The topic-selector-example2
example shows you how to
selectively consume messages using message selectors with topic consumers.
The transaction-failover
example demonstrates two servers coupled
as a live-backup pair for high availability (HA), and a client using a transacted JMS
session failing over from live to backup when the live server is
crashed.
HornetQ implements failover of client connections between live and backup servers. This is implemented by the sharing of a journal between the servers. When a live node crashes, the client connections can carry and continue to send and consume messages. When transacted sessions are used, once and only once message delivery is guaranteed.
The transactional
example shows you how to use a transactional
Session with HornetQ.
The xa-heuristic
example shows you how to make an XA heuristic
decision through HornetQ Management Interface. A heuristic decision is a unilateral
decision to commit or rollback an XA transaction branch after it has been
prepared.
The xa-receive
example shows you how message receiving behaves
in an XA transaction in HornetQ.
The xa-send
example shows you how message sending behaves in an
XA transaction in HornetQ.
To run a core example, simply cd
into the appropriate example
directory and type ant
Most of the Java EE examples can be run the following way. simply cd into the
appropriate example directory and type ant deploy
. This will create a
new JBoss AS profile and start the server. When the server is started from a different
window type ant run
to run the example. Some examples require further
steps, please refer to the examples documentation for further instructions.
An example that shows using an EJB and JMS together within a transaction.
This example demonstrates how to configure several properties on the HornetQ JCA resource adaptor.
This example demonstrates how to configure the HornetQ resource adapter to talk to a remote HornetQ server
A simple set of examples of message driven beans, including failover examples.
HornetQ allows the routing of messages via wildcard addresses.
If a queue is created with an address of say queue.news.#
then it
will receive any messages sent to addresses that match this, for instance queue.news.europe
or queue.news.usa
or queue.news.usa.sport
. If you create a consumer on this queue, this allows a consumer to consume messages which are
sent to a hierarchy of addresses.
In JMS terminology this allows "topic hierarchies" to be created.
To enable this functionality set the property wild-card-routing-enabled
in the hornetq-configuration.xml
file to true
. This is
true
by default.
For more information on the wild card syntax take a look at Chapter 13, Understanding the HornetQ Wildcard Syntax chapter, also see Section 11.1.64, “Topic Hierarchy”.
HornetQ uses a specific syntax for representing wildcards in security settings, address settings and when creating consumers.
The syntax is similar to that used by AMQP.
A HornetQ wildcard expression contains words delimited by the character '.
' (full stop).
The special characters '#
' and '*
' also have special
meaning and can take the place of a word.
The character '#
' means 'match any sequence of zero or more
words'.
The character '*
' means 'match a single word'.
So the wildcard 'news.europe.#' would match 'news.europe', 'news.europe.sport', 'news.europe.politics', and 'news.europe.politics.regional' but would not match 'news.usa', 'news.usa.sport' nor 'entertainment'.
The wildcard 'news.*' would match 'news.europe', but not 'news.europe.sport'.
The wildcard 'news.*.sport' would match 'news.europe.sport' and also 'news.usa.sport', but not 'news.europe.politics'.
HornetQ provides a powerful filter language based on a subset of the SQL 92 expression syntax.
It is the same as the syntax used for JMS selectors, but the predefined identifiers are different. For documentation on JMS selector syntax please the JMS javadoc for javax.jms.Message.
Filter expressions are used in several places in HornetQ
Predefined Queues. When pre-defining a queue, either in hornetq-configuration.xml
or hornetq-jms.xml
a filter
expression can be defined for a queue. Only messages that match the filter
expression will enter the queue.
Core bridges can be defined with an optional filter expression, only matching messages will be bridged (see Chapter 36, Core Bridges).
Diverts can be defined with an optional filter expression, only matching messages will be diverted (see Chapter 35, Diverting and Splitting Message Flows).
Filter are also used programmatically when creating consumers, queues and in several places as described in Chapter 30, Management.
There are some differences between JMS selector expressions and HornetQ core filter expressions. Whereas JMS selector expressions operate on a JMS message, HornetQ core filter expressions operate on a core message.
The following identifiers can be used in a core filter expressions to refer to attributes of the core message in an expression:
HQPriority
. To refer to the priority of a message. Message
priorities are integers with valid values from 0 - 9
. 0
is the lowest priority and 9
is the highest.
E.g. HQPriority = 3 AND animal = 'aardvark'
HQExpiration
. To refer to the expiration time of a message.
The value is a long integer.
HQDurable
. To refer to whether a message is durable or not.
The value is a string with valid values: DURABLE
or NON_DURABLE
.
HQTimestamp
. The timestamp of when the message was created.
The value is a long integer.
HQSize
. The size of a message in bytes. The value is an
integer.
Any other identifiers used in core filter expressions will be assumed to be properties of the message.
In this chapter we will describe how persistence works with HornetQ and how to configure it.
HornetQ ships with a high performance journal. Since HornetQ handles its own persistence, rather than relying on a database or other 3rd party persistence engine it is very highly optimised for the specific messaging use cases.
A HornetQ journal is an append only journal. It consists of a set of files on disk. Each file is pre-created to a fixed size and initially filled with padding. As operations are performed on the server, e.g. add message, update message, delete message, records are appended to the journal. When one journal file is full we move to the next one.
Because records are only appended, i.e. added to the end of the journal we minimise disk head movement, i.e. we minimise random access operations which is typically the slowest operation on a disk.
Making the file size configurable means that an optimal size can be chosen, i.e. making each file fit on a disk cylinder. Modern disk topologies are complex and we are not in control over which cylinder(s) the file is mapped onto so this is not an exact science. But by minimising the number of disk cylinders the file is using, we can minimise the amount of disk head movement, since an entire disk cylinder is accessible simply by the disk rotating - the head does not have to move.
As delete records are added to the journal, HornetQ has a sophisticated file garbage collection algorithm which can determine if a particular journal file is needed any more - i.e. has all its data been deleted in the same or other files. If so, the file can be reclaimed and re-used.
HornetQ also has a compaction algorithm which removes dead space from the journal and compresses up the data so it takes up less files on disk.
The journal also fully supports transactional operation if required, supporting both local and XA transactions.
The majority of the journal is written in Java, however we abstract out the interaction with the actual file system to allow different pluggable implementations. HornetQ ships with two implementations:
Java NIO.
The first implementation uses standard Java NIO to interface with the file system. This provides extremely good performance and runs on any platform where there's a Java 6+ runtime.
The second implementation uses a thin native code wrapper to talk to the Linux asynchronous IO library (AIO). With AIO, HornetQ will be called back when the data has made it to disk, allowing us to avoid explicit syncs altogether and simply send back confirmation of completion when AIO informs us that the data has been persisted.
Using AIO will typically provide even better performance than using Java NIO.
The AIO journal is only available when running Linux kernel 2.6 or later and after having installed libaio (if it's not already installed). For instructions on how to install libaio please see Section 15.5, “Installing AIO”.
Also, please note that AIO will only work with the following file systems: ext2, ext3, ext4, jfs, xfs. With other file systems, e.g. NFS it may appear to work, but it will fall back to a slower sychronous behaviour. Don't put the journal on a NFS share!
For more information on libaio please see Chapter 40, Libaio Native Libraries.
libaio is part of the kernel project.
The standard HornetQ core server uses two instances of the journal:
Bindings journal.
This journal is used to store bindings related data. That includes the set of queues that are deployed on the server and their attributes. It also stores data such as id sequence counters.
The bindings journal is always a NIO journal as it is typically low throughput compared to the message journal.
The files on this journal are prefixed as hornetq-bindings
.
Each file has a bindings
extension. File size is 1048576
, and it is located at the bindings folder.
JMS journal.
This journal instance stores all JMS related data, This is basically any JMS Queues, Topics and Connection Factories and any JNDI bindings for these resources.
Any JMS Resources created via the management API will be persisted to this journal. Any resources configured via configuration files will not. The JMS Journal will only be created if JMS is being used.
The files on this journal are prefixed as hornetq-jms
. Each
file has a jms
extension. File size is 1048576
, and it is located at the bindings folder.
Message journal.
This journal instance stores all message related data, including the message themselves and also duplicate-id caches.
By default HornetQ will try and use an AIO journal. If AIO is not available, e.g. the platform is not Linux with the correct kernel version or AIO has not been installed then it will automatically fall back to using Java NIO which is available on any Java platform.
The files on this journal are prefixed as hornetq-data
. Each
file has a hq
extension. File size is by the default 10485760
(configurable), and it is located at the journal
folder.
For large messages, HornetQ persists them outside the message journal. This is discussed in Chapter 23, Large Messages.
HornetQ can also be configured to page messages to disk in low memory situations. This is discussed in Chapter 24, Paging.
If no persistence is required at all, HornetQ can also be configured not to persist any data at all to storage as discussed in Section 15.6, “Configuring HornetQ for Zero Persistence”.
The bindings journal is configured using the following attributes in hornetq-configuration.xml
bindings-directory
This is the directory in which the bindings journal lives. The default value
is data/bindings
.
create-bindings-dir
If this is set to true
then the bindings directory will be
automatically created at the location specified in bindings-directory
if it does not already exist. The default
value is true
The message journal is configured using the following attributes in hornetq-configuration.xml
This is the directory in which the message journal lives. The default value is
data/journal
.
For the best performance, we recommend the journal is located on its own physical volume in order to minimise disk head movement. If the journal is on a volume which is shared with other processes which might be writing other files (e.g. bindings journal, database, or transaction coordinator) then the disk head may well be moving rapidly between these files as it writes them, thus drastically reducing performance.
When the message journal is stored on a SAN we recommend each journal instance that is stored on the SAN is given its own LUN (logical unit).
If this is set to true
then the journal directory will be
automatically created at the location specified in journal-directory
if it does not already exist. The default value
is true
Valid values are NIO
or ASYNCIO
.
Choosing NIO
chooses the Java NIO journal. Choosing
AIO
chooses the Linux asynchronous IO journal. If you
choose AIO
but are not running Linux or you do not have
libaio installed then HornetQ will detect this and automatically fall back to
using NIO
.
If this is set to true then HornetQ will make sure all transaction data is
flushed to disk on transaction boundaries (commit, prepare and rollback). The
default value is true
.
journal-sync-non-transactional
If this is set to true then HornetQ will make sure non transactional message
data (sends and acknowledgements) are flushed to disk each time. The default
value for this is true
.
The size of each journal file in bytes. The default value for this is 10485760
bytes (10MiB).
The minimum number of files the journal will maintain. When HornetQ starts and
there is no initial message data, HornetQ will pre-create journal-min-files
number of files.
Creating journal files and filling them with padding is a fairly expensive operation and we want to minimise doing this at run-time as files get filled. By precreating files, as one is filled the journal can immediately resume with the next one without pausing to create it.
Depending on how much data you expect your queues to contain at steady state you should tune this number of files to match that total amount of data.
Write requests are queued up before being submitted to the system for execution. This parameter controls the maximum number of write requests that can be in the IO queue at any one time. If the queue becomes full then writes will block until space is freed up.
When using NIO, this value should always be equal to 1
When using AIO, the default should be 500
.
The system maintains different defaults for this parameter depening on whether it's NIO or AIO (default for NIO is 1, default for AIO is 500)
There is a limit and the total max AIO can't be higher than what is configured at the OS level (/proc/sys/fs/aio-max-nr) usually at 65536.
Instead of flushing on every write that requires a flush, we maintain an internal buffer, and flush the entire buffer either when it is full, or when a timeout expires, whichever is sooner. This is used for both NIO and AIO and allows the system to scale better with many concurrent writes that require flushing.
This parameter controls the timeout at which the buffer will be flushed if it hasn't filled already. AIO can typically cope with a higher flush rate than NIO, so the system maintains different defaults for both NIO and AIO (default for NIO is 3333333 nanoseconds - 300 times per second, default for AIO is 500000 nanoseconds - ie. 2000 times per second).
By increasing the timeout, you may be able to increase system throughput at the expense of latency, the default parameters are chosen to give a reasonable balance between throughput and latency.
The size of the timed buffer on AIO. The default value is 490KiB
.
The minimal number of files before we can consider compacting the journal. The
compacting algorithm won't start until you have at least journal-compact-min-files
The default for this parameter is 10
The threshold to start compacting. When less than this percentage is
considered live data, we start compacting. Note also that compacting won't kick
in until you have at least journal-compact-min-files
data
files on the journal
The default for this parameter is 30
Most disks contain hardware write caches. A write cache can increase the apparent performance of the disk because writes just go into the cache and are then lazily written to the disk later.
This happens irrespective of whether you have executed a fsync() from the operating system or correctly synced data from inside a Java program!
By default many systems ship with disk write cache enabled. This means that even after syncing from the operating system there is no guarantee the data has actually made it to disk, so if a failure occurs, critical data can be lost.
Some more expensive disks have non volatile or battery backed write caches which won't necessarily lose data on event of failure, but you need to test them!
If your disk does not have an expensive non volatile or battery backed cache and it's not part of some kind of redundant array (e.g. RAID), and you value your data integrity you need to make sure disk write cache is disabled.
Be aware that disabling disk write cache can give you a nasty shock performance wise. If you've been used to using disks with write cache enabled in their default setting, unaware that your data integrity could be compromised, then disabling it will give you an idea of how fast your disk can perform when acting really reliably.
On Linux you can inspect and/or change your disk's write cache settings using the
tools hdparm
(for IDE disks) or sdparm
or
sginfo
(for SDSI/SATA disks)
On Windows you can check / change the setting by right clicking on the disk and clicking properties.
The Java NIO journal gives great performance, but If you are running HornetQ using
Linux Kernel 2.6 or later, we highly recommend you use the AIO
journal for the very best persistence performance.
It's not possible to use the AIO journal under other operating systems or earlier versions of the Linux kernel.
If you are running Linux kernel 2.6 or later and don't already have libaio
installed, you can easily install it using the following
steps:
Using yum, (e.g. on Fedora or Red Hat Enterprise Linux):
yum install libaio
Using aptitude, (e.g. on Ubuntu or Debian system):
apt-get install libaio
In some situations, zero persistence is sometimes required for a messaging system.
Configuring HornetQ to perform zero persistence is straightforward. Simply set the
parameter persistence-enabled
in hornetq-configuration.xml
to false
.
Please note that if you set this parameter to false, then zero persistence will occur. That means no bindings data, message data, large message data, duplicate id caches or paging data will be persisted.
You may want to inspect the existent records on each one of the journals used by HornetQ, and you can use the export/import tool for that purpose. The export/import are classes located at the hornetq-core.jar, you can export the journal as a text file by using this command:
java -cp hornetq-core.jar org.hornetq.core.journal.impl.ExportJournal
<JournalDirectory> <JournalPrefix> <FileExtension> <FileSize>
<FileOutput>
To import the file as binary data on the journal (Notice you also require netty.jar):
java -cp hornetq-core.jar:netty.jar org.hornetq.core.journal.impl.ImportJournal
<JournalDirectory> <JournalPrefix> <FileExtension> <FileSize>
<FileInput>
JournalDirectory: Use the configured folder for your selected folder. Example: ./hornetq/data/journal
JournalPrefix: Use the prefix for your selected journal, as discussed here
FileExtension: Use the extension for your selected journal, as discussed here
FileSize: Use the size for your selected journal, as discussed here
FileOutput: text file that will contain the exported data
HornetQ has a fully pluggable and highly flexible transport layer and defines its own Service Provider Interface (SPI) to make plugging in a new transport provider relatively straightforward.
In this chapter we'll describe the concepts required for understanding HornetQ transports and where and how they're configured.
One of the most important concepts in HornetQ transports is the
acceptor. Let's dive straight in and take a look at an acceptor
defined in xml in the configuration file hornetq-configuration.xml
.
<acceptors> <acceptor name="netty"> <factory-class> org.hornetq.core.remoting.impl.netty.NettyAcceptorFactory </factory-class> <param key="port" value="5446"/> </acceptor> </acceptors>
Acceptors are always defined inside an acceptors
element. There can
be one or more acceptors defined in the acceptors
element. There's no
upper limit to the number of acceptors per server.
Each acceptor defines a way in which connections can be made to the HornetQ server.
In the above example we're defining an acceptor that uses Netty to listen for connections at port
5446
.
The acceptor
element contains a sub-element factory-class
, this element defines the factory used to create acceptor
instances. In this case we're using Netty to listen for connections so we use the Netty
implementation of an AcceptorFactory
to do this. Basically, the
factory-class
element determines which pluggable transport we're
going to use to do the actual listening.
The acceptor
element can also be configured with zero or more
param
sub-elements. Each param
element defines
a key-value pair. These key-value pairs are used to configure the specific transport,
the set of valid key-value pairs depends on the specific transport be used and are
passed straight through to the underlying transport.
Examples of key-value pairs for a particular transport would be, say, to configure the IP address to bind to, or the port to listen at.
Whereas acceptors are used on the server to define how we accept connections, connectors are used by a client to define how it connects to a server.
Let's look at a connector defined in our hornetq-configuration.xml
file:
<connectors> <connector name="netty"> <factory-class> org.hornetq.core.remoting.impl.netty.NettyConnectorFactory </factory-class> <param key="port" value="5446"/> </connector> </connectors>
Connectors can be defined inside a connectors
element. There can be
one or more connectors defined in the connectors
element. There's no
upper limit to the number of connectors per server.
You make ask yourself, if connectors are used by the client to make connections then why are they defined on the server? There are a couple of reasons for this:
Sometimes the server acts as a client itself when it connects to another server, for example when one server is bridged to another, or when a server takes part in a cluster. In this cases the server needs to know how to connect to other servers. That's defined by connectors.
If you're using JMS and the server side JMS service to instantiate JMS
ConnectionFactory instances and bind them in JNDI, then when creating the
HornetQConnectionFactory
it needs to know what server
that connection factory will create connections to.
That's defined by the connector-ref
element in the hornetq-jms.xml
file on the server side. Let's take a look at a
snipped from a hornetq-jms.xml
file that shows a JMS
connection factory that references our netty connector defined in our hornetq-configuration.xml
file:
<connection-factory name="ConnectionFactory"> <connectors> <connector-ref connector-name="netty"/> </connectors> <entries> <entry name="ConnectionFactory"/> <entry name="XAConnectionFactory"/> </entries> </connection-factory>
How do we configure a core ClientSessionFactory
with the
information that it needs to connect with a server?
Connectors are also used indirectly when directly configuring a core ClientSessionFactory
to directly talk to a server. Although in this case
there's no need to define such a connector in the server side configuration, instead we
just create the parameters and tell the ClientSessionFactory
which
connector factory to use.
Here's an example of creating a ClientSessionFactory
which will
connect directly to the acceptor we defined earlier in this chapter, it uses the
standard Netty TCP transport and will try and connect on port 5446 to localhost
(default):
Map<String, Object> connectionParams = new HashMap<String, Object>(); connectionParams.put(org.hornetq.core.remoting.impl.netty.TransportConstants.PORT_PROP_NAME, 5446); TransportConfiguration transportConfiguration = new TransportConfiguration( "org.hornetq.core.remoting.impl.netty.NettyConnectorFactory", connectionParams); ServerLocator locator = HornetQClient.createServerLocatorWithoutHA(transportConfiguration); ClientSessionFactory sessionFactory = locator.createClientSessionFactory(); ClientSession session = sessionFactory.createSession(...); etc
Similarly, if you're using JMS, you can configure the JMS connection factory directly
on the client side without having to define a connector on the server side or define a
connection factory in hornetq-jms.xml
:
Map<String, Object> connectionParams = new HashMap<String, Object>(); connectionParams.put(org.hornetq.core.remoting.impl.netty.TransportConstants.PORT_PROP_NAME, 5446); TransportConfiguration transportConfiguration = new TransportConfiguration( "org.hornetq.core.remoting.impl.netty.NettyConnectorFactory", connectionParams); ConnectionFactory connectionFactory = HornetQJMSClient.createConnectionFactoryWithoutHA(JMSFactoryType.CF, transportConfiguration); Connection jmsConnection = connectionFactory.createConnection(); etc
Out of the box, HornetQ currently uses Netty, a high performance low level network library.
Our Netty transport can be configured in several different ways; to use old (blocking) Java IO, or NIO (non-blocking), also to use straightforward TCP sockets, SSL, or to tunnel over HTTP or HTTPS, on top of that we also provide a servlet transport.
We believe this caters for the vast majority of transport requirements.
Netty TCP is a simple unencrypted TCP sockets based transport. Netty TCP can be configured to use old blocking Java IO or non blocking Java NIO. We recommend you use the Java NIO on the server side for better scalability with many concurrent connections. However using Java old IO can sometimes give you better latency than NIO when you're not so worried about supporting many thousands of concurrent connections.
If you're running connections across an untrusted network please bear in mind this transport is unencrypted. You may want to look at the SSL or HTTPS configurations.
With the Netty TCP transport all connections are initiated from the client side. I.e. the server does not initiate any connections to the client. This works well with firewall policies that typically only allow connections to be initiated in one direction.
All the valid Netty transport keys are defined in the class org.hornetq.core.remoting.impl.netty.TransportConstants
. Most
parameters can be used either with acceptors or connectors, some only work with
acceptors. The following parameters can be used to configure Netty for simple
TCP:
use-nio
. If this is true
then Java
non blocking NIO will be used. If set to false
then old
blocking Java IO will be used.
If you require the server to handle many concurrent connections, we highly
recommend that you use non blocking Java NIO. Java NIO does not maintain a
thread per connection so can scale to many more concurrent connections than
with old blocking IO. If you don't require the server to handle many
concurrent connections, you might get slightly better performance by using
old (blocking) IO. The default value for this property is false
on the server side and false
on the
client side.
host
. This specifies the host name or IP address to
connect to (when configuring a connector) or to listen on (when configuring
an acceptor). The default value for this property is localhost
. When configuring acceptors, multiple hosts or IP
addresses can be specified by separating them with commas. It is also
possible to specify 0.0.0.0
to accept connection from all the
host's network interfaces. It's not valid to specify multiple addresses when
specifying the host for a connector; a connector makes a connection to one
specific address.
Don't forget to specify a host name or ip address! If you want your server able to accept connections from other nodes you must specify a hostname or ip address at which the acceptor will bind and listen for incoming connections. The default is localhost which of course is not accessible from remote nodes!
port
. This specified the port to connect to (when
configuring a connector) or to listen on (when configuring an acceptor). The
default value for this property is 5445
.
tcp-no-delay
. If this is true
then
Nagle's
algorithm will be enabled. The default value for this property
is true
.
tcp-send-buffer-size
. This parameter determines the
size of the TCP send buffer in bytes. The default value for this property is
32768
bytes (32KiB).
TCP buffer sizes should be tuned according to the bandwidth and latency of your network. Here's a good link that explains the theory behind this.
In summary TCP send/receive buffer sizes should be calculated as:
buffer_size = bandwidth * RTT.
Where bandwidth is in bytes per second and network
round trip time (RTT) is in seconds. RTT can be easily measured using the
ping
utility.
For fast networks you may want to increase the buffer sizes from the defaults.
tcp-receive-buffer-size
. This parameter determines the
size of the TCP receive buffer in bytes. The default value for this property
is 32768
bytes (32KiB).
batch-delay
. Before writing packets to the transport,
HornetQ can be configured to batch up writes for a maximum of batch-delay
milliseconds. This can increase overall
throughput for very small messages. It does so at the expense of an increase
in average latency for message transfer. The default value for this property
is 0
ms.
direct-deliver
. When a message arrives on the server
and is delivered to waiting consumers, by default, the delivery is done on
the same thread as that on which the message arrived. This gives good latency
in environments with relatively small messages and a small number of consumers,
but at the cost of overall throughput and scalability - especially on multi-core
machines. If you want the lowest latency and a possible reduction in throughput
then you can use the default value for direct-deliver
(i.e.
true). If you are willing to take some small extra hit on latency but want the
highest throughput set direct-deliver
to false
.
nio-remoting-threads
. When configured to use NIO,
HornetQ will, by default, use a number of threads equal to three times the
number of cores (or hyper-threads) as reported by Runtime.getRuntime().availableProcessors()
for processing
incoming packets. If you want to override this value, you can set the number
of threads by specifying this parameter. The default value for this
parameter is -1
which means use the value from Runtime.getRuntime().availableProcessors()
* 3.
Netty SSL is similar to the Netty TCP transport but it provides additional security by encrypting TCP connections using the Secure Sockets Layer SSL
Please see the examples for a full working example of using Netty SSL.
Netty SSL uses all the same properties as Netty TCP but adds the following additional properties:
ssl-enabled
. Must be true
to enable
SSL.
key-store-path
. This is the path to the SSL key store
on the client which holds the client certificates. Although this value is
configured on the server, it is downloaded and used by the client. However,
it can be overridden on the client-side by using the customary
"javax.net.ssl.keyStore" system property.
key-store-password
. This is the password for the client
certificate key store on the client. Although this value is configured on
the server, it is downloaded and used by the client. However, it can be
overridden on the client-side by using the customary
"javax.net.ssl.keyStorePassword" system property.
trust-store-path
. This is the path to the trusted
client certificate store on the server.
trust-store-password
. This is the password to the
trusted client certificate store on the server.
Netty HTTP tunnels packets over the HTTP protocol. It can be useful in scenarios where firewalls only allow HTTP traffice to pass.
Please see the examples for a full working example of using Netty HTTP.
Netty HTTP uses the same properties as Netty TCP but adds the following additional properties:
http-enabled
. Must be true
to enable
HTTP.
http-client-idle-time
. How long a client can be idle
before sending an empty http request to keep the connection alive
http-client-idle-scan-period
. How often, in
milliseconds, to scan for idle clients
http-response-time
. How long the server can wait before
sending an empty http response to keep the connection alive
http-server-scan-period
. How often, in milliseconds, to
scan for clients needing responses
http-requires-session-id
. If true the client will wait
after the first call to receive a session id. Used the http connector is
connecting to servlet acceptor (not recommended)
We also provide a Netty servlet transport for use with HornetQ. The servlet transport allows HornetQ traffic to be tunneled over HTTP to a servlet running in a servlet engine which then redirects it to an in-VM HornetQ server.
The servlet transport differs from the Netty HTTP transport in that, with the HTTP transport HornetQ effectively acts a web server listening for HTTP traffic on, e.g. port 80 or 8080, whereas with the servlet transport HornetQ traffic is proxied through a servlet engine which may already be serving web site or other applications. This allows HornetQ to be used where corporate policies may only allow a single web server listening on an HTTP port, and this needs to serve all applications including messaging.
Please see the examples for a full working example of the servlet transport being used.
To configure a servlet engine to work the Netty Servlet transport we need to do the following things:
Deploy the servlet. Here's an example web.xml describing a web application that uses the servlet:
<?xml version="1.0" encoding="UTF-8"?> <web-app xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd" version="2.4"> <servlet> <servlet-name>HornetQServlet</servlet-name> <servlet-class>org.jboss.netty.channel.socket.http.HttpTunnelingServlet</servlet-class> <init-param> <param-name>endpoint</param-name> <param-value>local:org.hornetq</param-value> </init-param> <load-on-startup>1</load-on-startup> </servlet> <servlet-mapping> <servlet-name>HornetQServlet</servlet-name> <url-pattern>/HornetQServlet</url-pattern> </servlet-mapping> </web-app>
We also need to add a special Netty invm acceptor on the server side configuration.
Here's a snippet from the hornetq-configuration.xml
file showing that acceptor being defined:
<acceptors> <acceptor name="netty-invm"> <factory-class> org.hornetq.core.remoting.impl.netty.NettyAcceptorFactory </factory-class> <param key="use-invm" value="true"/> <param key="host" value="org.hornetq"/> </acceptor> </acceptors>
Lastly we need a connector for the client, this again will be configured
in the hornetq-configuration.xml
file as such:
<connectors> <connector name="netty-servlet"> <factory-class> org.hornetq.core.remoting.impl.netty.NettyConnectorFactory </factory-class> <param key="host" value="localhost"/> <param key="port" value="8080"/> <param key="use-servlet" value="true"/> <param key="servlet-path" value="/messaging/HornetQServlet"/> </connector> </connectors>
Heres a list of the init params and what they are used for
endpoint - This is the name of the netty acceptor that the servlet will
forward its packets to. You can see it matches the name of the host
param.
The servlet pattern configured in the web.xml
is the path of
the URL that is used. The connector param servlet-path
on the
connector config must match this using the application context of the web app if
there is one.
Its also possible to use the servlet transport over SSL. simply add the following configuration to the connector:
<connector name="netty-servlet"> <factory-class>org.hornetq.core.remoting.impl.netty.NettyConnectorFactory</factory-class> <param key="host" value="localhost"/> <param key="port" value="8443"/> <param key="use-servlet" value="true"/> <param key="servlet-path" value="/messaging/HornetQServlet"/> <param key="ssl-enabled" value="true"/> <param key="key-store-path" value="path to a keystoree"/> <param key="key-store-password" value="keystore password"/> </connector>
You will also have to configure the Application server to use a KeyStore. Edit the
server.xml
file that can be found under server/default/deploy/jbossweb.sar
of the Application Server
installation and edit the SSL/TLS connector configuration to look like the
following:
<Connector protocol="HTTP/1.1" SSLEnabled="true" port="8443" address="${jboss.bind.address}" scheme="https" secure="true" clientAuth="false" keystoreFile="path to a keystore" keystorePass="keystore password" sslProtocol = "TLS" />
In both cases you will need to provide a keystore and password. Take a look at the servlet ssl example shipped with HornetQ for more detail.
In this section we will discuss connection time-to-live (TTL) and explain how HornetQ deals with crashed clients and clients which have exited without cleanly closing their resources.
Before a HornetQ client application exits it is considered good practice that it
should close its resources in a controlled manner, using a finally
block.
Here's an example of a well behaved core client application closing its session and session factory in a finally block:
ServerLocator locator = null; ClientSessionFactory sf = null; ClientSession session = null; try { locator = HornetQClient.createServerLocatorWithoutHA(..); sf = locator.createClientSessionFactory();; session = sf.createSession(...); ... do some stuff with the session... } finally { if (session != null) { session.close(); } if (sf != null) { sf.close(); } if(locator != null) { locator.close(); } }
And here's an example of a well behaved JMS client application:
Connection jmsConnection = null; try { ConnectionFactory jmsConnectionFactory = HornetQJMSClient.createConnectionFactoryWithoutHA(...); jmsConnection = jmsConnectionFactory.createConnection(); ... do some stuff with the connection... } finally { if (connection != null) { connection.close(); } }
Unfortunately users don't always write well behaved applications, and sometimes clients just crash so they don't have a chance to clean up their resources!
If this occurs then it can leave server side resources, like sessions, hanging on the server. If these were not removed they would cause a resource leak on the server and over time this result in the server running out of memory or other resources.
We have to balance the requirement for cleaning up dead client resources with the fact that sometimes the network between the client and the server can fail and then come back, allowing the client to reconnect. HornetQ supports client reconnection, so we don't want to clean up "dead" server side resources too soon or this will prevent any client from reconnecting, as it won't be able to find its old sessions on the server.
HornetQ makes all of this configurable. For each ClientSessionFactory
we define a connection TTL.
Basically, the TTL determines how long the server will keep a connection alive in the
absence of any data arriving from the client. The client will automatically send "ping"
packets periodically to prevent the server from closing it down. If the server doesn't
receive any packets on a connection for the connection TTL time, then it will
automatically close all the sessions on the server that relate to that
connection.
If you're using JMS, the connection TTL is defined by the ConnectionTTL
attribute on a HornetQConnectionFactory
instance, or if you're deploying JMS connection factory instances direct into JNDI on
the server side, you can specify it in the xml config, using the parameter connection-ttl
.
The default value for connection ttl is 60000
ms, i.e. 1 minute. A
value of -1
for ConnectionTTL
means the server
will never time out the connection on the server side.
If you do not wish clients to be able to specify their own connection TTL, you can
override all values used by a global value set on the server side. This can be done by
specifying the connection-ttl-override
attribute in the server side
configuration. The default value for connection-ttl-override
is
-1
which means "do not override" (i.e. let clients use their own
values).
As previously discussed, it's important that all core client sessions and JMS
connections are always closed explicitly in a finally
block when
you are finished using them.
If you fail to do so, HornetQ will detect this at garbage collection time, and log a warning similar to the following in the logs (If you are using JMS the warning will involve a JMS connection not a client session):
[Finalizer] 20:14:43,244 WARNING [org.hornetq.core.client.impl.DelegatingSession] I'm closing a ClientSession you left open. Please make sure you close all ClientSessions explicitly before let ting them go out of scope! [Finalizer] 20:14:43,244 WARNING [org.hornetq.core.client.impl.DelegatingSession] The session you didn't close was created here: java.lang.Exception at org.hornetq.core.client.impl.DelegatingSession.<init>(DelegatingSession.java:83) at org.acme.yourproject.YourClass (YourClass.java:666)
HornetQ will then close the connection / client session for you.
Note that the log will also tell you the exact line of your user code where you created the JMS connection / client session that you later did not close. This will enable you to pinpoint the error in your code and correct it appropriately.
In the previous section we discussed how the client sends pings to the server and how "dead" connection resources are cleaned up by the server. There's also another reason for pinging, and that's for the client to be able to detect that the server or network has failed.
As long as the client is receiving data from the server it will consider the connection to be still alive.
If the client does not receive any packets for client-failure-check-period
milliseconds then it will consider the
connection failed and will either initiate failover, or call any FailureListener
instances (or ExceptionListener
instances if you are using JMS) depending on how it has been configured.
If you're using JMS it's defined by the ClientFailureCheckPeriod
attribute on a HornetQConnectionFactory
instance, or if you're
deploying JMS connection factory instances direct into JNDI on the server side, you can
specify it in the hornetq-jms.xml
configuration file, using the
parameter client-failure-check-period
.
The default value for client failure check period is 30000
ms, i.e.
30 seconds. A value of -1
means the client will never fail the
connection on the client side if no data is received from the server. Typically this is
much lower than connection TTL to allow clients to reconnect in case of transitory
failure.
By default, packets received on the server side are executed on the remoting thread.
It is possible instead to use a thread from a thread pool to handle some packets so
that the remoting thread is not tied up for too long. However, please note that
processing operations asynchronously on another thread adds a little more latency.
Please note that most short running operations are always handled on the remoting thread for performance reasons.
To enable asynchronous connection execution, set the parameter async-connection-execution-enabled
in hornetq-configuration.xml
to true
(default value is
true
).
HornetQ has its own Resource Manager for handling the lifespan of JTA transactions. When a transaction is started the resource manager is notified and keeps a record of the transaction and its current state. It is possible in some cases for a transaction to be started but then forgotten about. Maybe the client died and never came back. If this happens then the transaction will just sit there indefinitely.
To cope with this HornetQ can, if configured, scan for old transactions and rollback any
it finds. The default for this is 3000000 milliseconds (5 minutes), i.e. any transactions older
than 5 minutes are removed. This timeout can be changed by editing the transaction-timeout
property in hornetq-configuration.xml
(value must be in milliseconds).
The property transaction-timeout-scan-period
configures how often, in
milliseconds, to scan for old transactions.
Please note that HornetQ will not unilaterally rollback any XA transactions in a prepared state - this must be heuristically rolled back via the management API if you are sure they will never be resolved by the transaction manager.
Flow control is used to limit the flow of data between a client and server, or a server and another server in order to prevent the client or server being overwhelmed with data.
This controls the flow of data between the server and the client as the client consumes
messages. For performance reasons clients normally buffer messages before delivering to the
consumer via the receive()
method or asynchronously via a message
listener. If the consumer cannot process messages as fast as they are being delivered and
stored in the internal buffer, then you could end up with a situation where messages would
keep building up possibly causing out of memory on the client if they cannot be processed
in time.
By default, HornetQ consumers buffer messages from the server in a client side buffer before the client consumes them. This improves performance: otherwise every time the client consumes a message, HornetQ would have to go the server to request the next message. In turn, this message would then get sent to the client side, if one was available.
A network round trip would be involved for every message and considerably reduce performance.
To prevent this, HornetQ pre-fetches messages into a buffer on each consumer. The
total maximum size of messages (in bytes) that will be buffered on each consumer is
determined by the consumer-window-size
parameter.
By default, the consumer-window-size
is set to 1 MiB (1024 * 1024
bytes).
The value can be:
-1
for an unbounded buffer
0
to not buffer any messages. See Section 11.1.40, “No Consumer Buffering” for working example of a consumer
with no buffering.
>0
for a buffer with the given maximum size in
bytes.
Setting the consumer window size can considerably improve performance depending on the messaging use case. As an example, let's consider the two extremes:
Fast consumers can process messages as fast as they consume them (or even faster)
To allow fast consumers, set the consumer-window-size
to
-1. This will allow unbounded message buffering on the
client side.
Use this setting with caution: it can overflow the client memory if the consumer is not able to process messages as fast as it receives them.
Slow consumers takes significant time to process each message and it is desirable to prevent buffering messages on the client side so that they can be delivered to another consumer instead.
Consider a situation where a queue has 2 consumers; 1 of which is very slow. Messages are delivered in a round robin fashion to both consumers, the fast consumer processes all of its messages very quickly until its buffer is empty. At this point there are still messages awaiting to be processed in the buffer of the slow consumer thus preventing them being processed by the fast consumer. The fast consumer is therefore sitting idle when it could be processing the other messages.
To allow slow consumers, set the consumer-window-size
to
0 (for no buffer at all). This will prevent the slow consumer from buffering
any messages on the client side. Messages will remain on the server side ready
to be consumed by other consumers.
Setting this to 0 can give deterministic distribution between multiple consumers on a queue.
Most of the consumers cannot be clearly identified as fast or slow consumers but are
in-between. In that case, setting the value of consumer-window-size
to optimize performance depends on the messaging use case and requires benchmarks to
find the optimal value, but a value of 1MiB is fine in most cases.
If HornetQ Core API is used, the consumer window size is specified by ClientSessionFactory.setConsumerWindowSize()
method and some of the
ClientSession.createConsumer()
methods.
if JNDI is used to look up the connection factory, the consumer window size is
configured in hornetq-jms.xml
:
<connection-factory name="ConnectionFactory"> <connectors> <connector-ref connector-name="netty-connector"/> </connectors> <entries> <entry name="ConnectionFactory"/> </entries> <!-- Set the consumer window size to 0 to have *no* buffer on the client side --> <consumer-window-size>0</consumer-window-size> </connection-factory>
If the connection factory is directly instantiated, the consumer window size is
specified by HornetQConnectionFactory.setConsumerWindowSize()
method.
Please see Section 11.1.40, “No Consumer Buffering” for an example which shows how to configure HornetQ to prevent consumer buffering when dealing with slow consumers.
It is also possible to control the rate at which a consumer can consume messages. This is a form of throttling and can be used to make sure that a consumer never consumes messages at a rate faster than the rate specified.
The rate must be a positive integer to enable this functionality and is the maximum
desired message consumption rate specified in units of messages per second. Setting this
to -1
disables rate limited flow control. The default value is
-1
.
Please see Section 11.1.15, “Message Consumer Rate Limiting” for a working example of limiting consumer rate.
If the HornetQ core API is being used the rate can be set via the ClientSessionFactory.setConsumerMaxRate(int consumerMaxRate)
method or
alternatively via some of the ClientSession.createConsumer()
methods.
If JNDI is used to look up the connection factory, the max rate can be configured
in hornetq-jms.xml
:
<connection-factory name="ConnectionFactory"> <connectors> <connector-ref connector-name="netty-connector"/> </connectors> <entries> <entry name="ConnectionFactory"/> </entries> <!-- We limit consumers created on this connection factory to consume messages at a maximum rate of 10 messages per sec --> <consumer-max-rate>10</consumer-max-rate> </connection-factory>
If the connection factory is directly instantiated, the max rate size can be set
via the HornetQConnectionFactory.setConsumerMaxRate(int
consumerMaxRate)
method.
Rate limited flow control can be used in conjunction with window based flow control. Rate limited flow control only effects how many messages a client can consume in a second and not how many messages are in its buffer. So if you had a slow rate limit and a high window based limit the clients internal buffer would soon fill up with messages.
Please see Section 11.1.15, “Message Consumer Rate Limiting” for an example which shows how to configure HornetQ to prevent consumer buffering when dealing with slow consumers.
HornetQ also can limit the amount of data sent from a client to a server to prevent the server being overwhelmed.
In a similar way to consumer window based flow control, HornetQ producers, by default, can only send messages to an address as long as they have sufficient credits to do so. The amount of credits required to send a message is given by the size of the message.
As producers run low on credits they request more from the server, when the server sends them more credits they can send more messages.
The amount of credits a producer requests in one go is known as the window size.
The window size therefore determines the amount of bytes that can be in-flight at any one time before more need to be requested - this prevents the remoting connection from getting overloaded.
If the HornetQ core API is being used, window size can be set via the ClientSessionFactory.setProducerWindowSize(int producerWindowSize)
method.
If JNDI is used to look up the connection factory, the producer window size can be
configured in hornetq-jms.xml
:
<connection-factory name="ConnectionFactory"> <connectors> <connector-ref connector-name="netty-connector"/> </connectors> <entries> <entry name="ConnectionFactory"/> </entries> <producer-window-size>10</producer-window-size> </connection-factory>
If the connection factory is directly instantiated, the producer window size can
be set via the HornetQConnectionFactory.setProducerWindowSize(int
producerWindowSize)
method.
Normally the server will always give the same number of credits as have been requested. However, it is also possible to set a maximum size on any address, and the server will never send more credits than could cause the address's upper memory limit to be exceeded.
For example, if I have a JMS queue called "myqueue", I could set the maximum memory size to 10MiB, and the the server will control the number of credits sent to any producers which are sending any messages to myqueue such that the total messages in the queue never exceeds 10MiB.
When the address gets full, producers will block on the client side until more space frees up on the address, i.e. until messages are consumed from the queue thus freeing up space for more messages to be sent.
We call this blocking producer flow control, and it's an efficient way to prevent the server running out of memory due to producers sending more messages than can be handled at any time.
It is an alternative approach to paging, which does not block producers but instead pages messages to storage.
To configure an address with a maximum size and tell the server that you want to
block producers for this address if it becomes full, you need to define an
AddressSettings (Section 25.3, “Configuring Queues Via Address Settings”) block for the
address and specify max-size-bytes
and address-full-policy
The address block applies to all queues registered to that address. I.e. the total
memory for all queues bound to that address will not exceed max-size-bytes
. In the case of JMS topics this means the total memory of all subscriptions in the topic won't
exceed max-size-bytes.
Here's an example:
<address-settings> <address-setting match="jms.queue.exampleQueue"> <max-size-bytes>100000</max-size-bytes> <address-full-policy>BLOCK</address-full-policy> </address-setting> </address-settings>
The above example would set the max size of the JMS queue "exampleQueue" to be 100000 bytes and would block any producers sending to that address to prevent that max size being exceeded.
Note the policy must be set to BLOCK
to enable blocking producer
flow control.
Note that in the default configuration all addresses are set to block producers after 10 MiB of message data
is in the address. This means you cannot send more than 10MiB of message data to an address without it being consumed before the producers
will be blocked. If you do not want this behaviour increase the max-size-bytes
parameter or change the
address full message policy.
HornetQ also allows the rate a producer can emit message to be limited, in units of messages per second. By specifying such a rate, HornetQ will ensure that producer never produces messages at a rate higher than that specified.
The rate must be a positive integer to enable this functionality and is the maximum
desired message consumption rate specified in units of messages per second. Setting this
to -1
disables rate limited flow control. The default value is
-1
.
Please see the Section 11.1.44, “Message Producer Rate Limiting” for a working example of limiting producer rate.
If the HornetQ core API is being used the rate can be set via the ClientSessionFactory.setProducerMaxRate(int consumerMaxRate)
method or
alternatively via some of the ClientSession.createProducer()
methods.
If JNDI is used to look up the connection factory, the max rate can be configured
in hornetq-jms.xml
:
<connection-factory name="ConnectionFactory"> <connectors> <connector-ref connector-name="netty-connector"/> </connectors> <entries> <entry name="ConnectionFactory"/> </entries> <!-- We limit producers created on this connection factory to produce messages at a maximum rate of 10 messages per sec --> <producer-max-rate>10</producer-max-rate> </connection-factory>
If the connection factory is directly instantiated, the max rate size can be set
via the HornetQConnectionFactory.setProducerMaxRate(int
consumerMaxRate)
method.
When committing or rolling back a transaction with HornetQ, the request to commit or rollback is sent to the server, and the call will block on the client side until a response has been received from the server that the commit or rollback was executed.
When the commit or rollback is received on the server, it will be committed to the
journal, and depending on the value of the parameter journal-sync-transactional
the server will ensure that the commit or
rollback is durably persisted to storage before sending the response back to the client.
If this parameter has the value false
then commit or rollback may not
actually get persisted to storage until some time after the response has been sent to
the client. In event of server failure this may mean the commit or rollback never gets
persisted to storage. The default value of this parameter is true
so
the client can be sure all transaction commits or rollbacks have been persisted to
storage by the time the call to commit or rollback returns.
Setting this parameter to false
can improve performance at the
expense of some loss of transaction durability.
This parameter is set in hornetq-configuration.xml
If you are sending messages to a server using a non transacted session, HornetQ can be configured to block the call to send until the message has definitely reached the server, and a response has been sent back to the client. This can be configured individually for durable and non-durable messages, and is determined by the following two parameters:
BlockOnDurableSend
. If this is set to true
then all calls to send for durable messages on non
transacted sessions will block until the message has reached the server, and a
response has been sent back. The default value is true
.
BlockOnNonDurableSend
. If this is set to true
then all calls to send for non-durable messages on non
transacted sessions will block until the message has reached the server, and a
response has been sent back. The default value is false
.
Setting block on sends to true
can reduce performance since each
send requires a network round trip before the next send can be performed. This means the
performance of sending messages will be limited by the network round trip time (RTT) of
your network, rather than the bandwidth of your network. For better performance we
recommend either batching many messages sends together in a transaction since with a
transactional session, only the commit / rollback blocks not every send, or, using
HornetQ's advanced asynchronous send acknowledgements feature
described in Section 20.4, “Asynchronous Send Acknowledgements”.
If you are using JMS and you're using the JMS service on the server to load your JMS
connection factory instances into JNDI then these parameters can be configured in
hornetq-jms.xml
using the elements block-on-durable-send
and block-on-non-durable-send
. If you're using JMS but not using JNDI then
you can set these values directly on the HornetQConnectionFactory
instance using the appropriate setter methods.
If you're using core you can set these values directly on the ClientSessionFactory
instance using the appropriate setter
methods.
When the server receives a message sent from a non transactional session, and that
message is durable and the message is routed to at least one durable queue, then the
server will persist the message in permanent storage. If the journal parameter journal-sync-non-transactional
is set to true
the
server will not send a response back to the client until the message has been persisted
and the server has a guarantee that the data has been persisted to disk. The default
value for this parameter is true
.
If you are acknowledging the delivery of a message at the client side using a non
transacted session, HornetQ can be configured to block the call to acknowledge until the
acknowledge has definitely reached the server, and a response has been sent back to the
client. This is configured with the parameter BlockOnAcknowledge
. If
this is set to true
then all calls to acknowledge on non transacted
sessions will block until the acknowledge has reached the server, and a response has
been sent back. You might want to set this to true
if you want to
implement a strict at most once delivery policy. The default value
is false
If you are using a non transacted session but want a guarantee that every message sent to the server has reached it, then, as discussed in Section 20.2, “Guarantees of Non Transactional Message Sends”, you can configure HornetQ to block the call to send until the server has received the message, persisted it and sent back a response. This works well but has a severe performance penalty - each call to send needs to block for at least the time of a network round trip (RTT) - the performance of sending is thus limited by the latency of the network, not limited by the network bandwidth.
Let's do a little bit of maths to see how severe that is. We'll consider a standard 1Gib ethernet network with a network round trip between the server and the client of 0.25 ms.
With a RTT of 0.25 ms, the client can send at most 1000/ 0.25 = 4000 messages per second if it blocks on each message send.
If each message is < 1500 bytes and a standard 1500 bytes MTU size is used on the network, then a 1GiB network has a theoretical upper limit of (1024 * 1024 * 1024 / 8) / 1500 = 89478 messages per second if messages are sent without blocking! These figures aren't an exact science but you can clearly see that being limited by network RTT can have serious effect on performance.
To remedy this, HornetQ provides an advanced new feature called asynchronous send acknowledgements. With this feature, HornetQ can be configured to send messages without blocking in one direction and asynchronously getting acknowledgement from the server that the messages were received in a separate stream. By de-coupling the send from the acknowledgement of the send, the system is not limited by the network RTT, but is limited by the network bandwidth. Consequently better throughput can be achieved than is possible using a blocking approach, while at the same time having absolute guarantees that messages have successfully reached the server.
The window size for send acknowledgements is determined by the confirmation-window-size parameter on the connection factory or client session factory. Please see Chapter 34, Client Reconnection and Session Reattachment for more info on this.
To use the feature using the core API, you implement the interface org.hornetq.api.core.client.SendAcknowledgementHandler
and set a handler
instance on your ClientSession
.
Then, you just send messages as normal using your ClientSession
, and as messages reach the server, the server will send
back an acknowledgement of the send asynchronously, and some time later you are
informed at the client side by HornetQ calling your handler's sendAcknowledged(ClientMessage message)
method, passing in a
reference to the message that was sent.
To enable asynchronous send acknowledgements you must make sure confirmation-window-size
is set to a positive integer value, e.g. 10MiB
Please see Section 11.1.53, “Send Acknowledgements” for a full working example.
Messages can be delivered unsuccessfully (e.g. if the transacted session used to consume them is rolled back). Such a message goes back to its queue ready to be redelivered. However, this means it is possible for a message to be delivered again and again without any success and remain in the queue, clogging the system.
There are 2 ways to deal with these undelivered messages:
Delayed redelivery.
It is possible to delay messages redelivery to let the client some time to recover from transient failures and not overload its network or CPU resources
Dead Letter Address.
It is also possible to configure a dead letter address so that after a specified number of unsuccessful deliveries, messages are removed from the queue and will not be delivered again
Both options can be combined for maximum flexibility.
Delaying redelivery can often be useful in the case that clients regularly fail or rollback. Without a delayed redelivery, the system can get into a "thrashing" state, with delivery being attempted, the client rolling back, and delivery being re-attempted ad infinitum in quick succession, consuming valuable CPU and network resources.
Delayed redelivery is defined in the address-setting configuration:
<!-- delay redelivery of messages for 5s --> <address-setting match="jms.queue.exampleQueue"> <redelivery-delay>5000</redelivery-delay> </address-setting>
If a redelivery-delay
is specified, HornetQ will wait this delay
before redelivering the messages
By default, there is no redelivery delay (redelivery-delay
is set
to 0).
Address wildcards can be used to configure redelivery delay for a set of addresses (see Chapter 13, Understanding the HornetQ Wildcard Syntax), so you don't have to specify redelivery delay individually for each address.
See Section 11.1.17, “Delayed Redelivery” for an example which shows how delayed redelivery is configured and used with JMS.
To prevent a client infinitely receiving the same undelivered message (regardless of what is causing the unsuccessful deliveries), messaging systems define dead letter addresses: after a specified unsuccessful delivery attempts, the message is removed from the queue and send instead to a dead letter address.
Any such messages can then be diverted to queue(s) where they can later be perused by the system administrator for action to be taken.
HornetQ's addresses can be assigned a dead letter address. Once the messages have be unsuccessfully delivered for a given number of attempts, they are removed from the queue and sent to the dead letter address. These dead letter messages can later be consumed for further inspection.
Dead letter address is defined in the address-setting configuration:
<!-- undelivered messages in exampleQueue will be sent to the dead letter address deadLetterQueue after 3 unsuccessful delivery attempts --> <address-setting match="jms.queue.exampleQueue"> <dead-letter-address>jms.queue.deadLetterQueue</dead-letter-address> <max-delivery-attempts>3</max-delivery-attempts> </address-setting>
If a dead-letter-address
is not specified, messages will removed
after max-delivery-attempts
unsuccessful attempts.
By default, messages are redelivered 10 times at the maximum. Set max-delivery-attempts
to -1 for infinite redeliveries.
For example, a dead letter can be set globally for a set of matching addresses and
you can set max-delivery-attempts
to -1 for a specific address
setting to allow infinite redeliveries only for this address.
Address wildcards can be used to configure dead letter settings for a set of addresses (see Chapter 13, Understanding the HornetQ Wildcard Syntax).
Dead letter messages which are consumed from a dead letter address have the following property:
_HQ_ORIG_ADDRESS
a String property containing the original address of the dead letter message
See Section 11.1.16, “Dead Letter” for an example which shows how dead letter is configured and used with JMS.
In normal use, HornetQ does not update delivery count persistently until a message is rolled back (i.e. the delivery count is not updated before the message is delivered to the consumer). In most messaging use cases, the messages are consumed, acknowledged and forgotten as soon as they are consumed. In these cases, updating the delivery count persistently before delivering the message would add an extra persistent step for each message delivered, implying a significant performance penalty.
However, if the delivery count is not updated persistently before the message delivery
happens, in the event of a server crash, messages might have been delivered but that will
not have been reflected in the delivery count. During the recovery phase, the server will
not have knowledge of that and will deliver the message with redelivered
set to false
while it should be true
.
As this behavior breaks strict JMS semantics, HornetQ allows to persist delivery count before message delivery but disabled it by default for performance implications.
To enable it, set persist-delivery-count-before-delivery
to true
in hornetq-configuration.xml
:
<persist-delivery-count-before-delivery>true</persist-delivery-count-before-delivery>
Messages can be set with an optional time to live when sending them.
HornetQ will not deliver a message to a consumer after it's time to live has been exceeded. If the message hasn't been delivered by the time that time to live is reached the server can discard it.
HornetQ's addresses can be assigned a expiry address so that, when messages are expired, they are removed from the queue and sent to the expiry address. Many different queues can be bound to an expiry address. These expired messages can later be consumed for further inspection.
Using HornetQ Core API, you can set an expiration time directly on the message:
// message will expire in 5000ms from now message.setExpiration(System.currentTimeMillis() + 5000);
JMS MessageProducer allows to set a TimeToLive for the messages it sent:
// messages sent by this producer will be retained for 5s (5000ms) before expiration producer.setTimeToLive(5000);
Expired messages which are consumed from an expiry address have the following properties:
_HQ_ORIG_ADDRESS
a String property containing the original address of the expired message
_HQ_ACTUAL_EXPIRY
a Long property containing the actual expiration time of the expired message
Expiry address are defined in the address-setting configuration:
<!-- expired messages in exampleQueue will be sent to the expiry address expiryQueue --> <address-setting match="jms.queue.exampleQueue"> <expiry-address>jms.queue.expiryQueue</expiry-address> </address-setting>
If messages are expired and no expiry address is specified, messages are simply removed from the queue and dropped. Address wildcards can be used to configure expiry address for a set of addresses (see Chapter 13, Understanding the HornetQ Wildcard Syntax).
A reaper thread will periodically inspect the queues to check if messages have expired.
The reaper thread can be configured with the following properties in hornetq-configuration.xml
message-expiry-scan-period
How often the queues will be scanned to detect expired messages (in milliseconds,
default is 30000ms, set to -1
to disable the reaper thread)
message-expiry-thread-priority
The reaper thread priority (it must be between 0 and 9, 9 being the highest priority, default is 3)
See Section 11.1.22, “Message Expiration” for an example which shows how message expiry is configured and used with JMS.
HornetQ supports sending and receiving of huge messages, even when the client and server are running with limited memory. The only realistic limit to the size of a message that can be sent or consumed is the amount of disk space you have available. We have tested sending and consuming messages up to 8 GiB in size with a client and server running in just 50MiB of RAM!
To send a large message, the user can set an InputStream
on a message
body, and when that message is sent, HornetQ will read the InputStream
. A
FileInputStream
could be used for example to send a huge message from
a huge file on disk.
As the InputStream
is read the data is sent to the server as a stream
of fragments. The server persists these fragments to disk as it receives them and when the
time comes to deliver them to a consumer they are read back of the disk, also in fragments
and sent down the wire. When the consumer receives a large message it initially receives
just the message with an empty body, it can then set an OutputStream
on
the message to stream the huge message body to a file on disk or elsewhere. At no time is
the entire message body stored fully in memory, either on the client or the server.
Large messages are stored on a disk directory on the server side, as configured on the main configuration file.
The configuration property large-messages-directory
specifies where
large messages are stored.
<configuration xmlns="urn:hornetq" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="urn:hornetq /schema/hornetq-configuration.xsd"> ... <large-messages-directory>/data/large-messages</large-messages-directory> ... </configuration
By default the large message directory is data/largemessages
For the best performance we recommend large messages directory is stored on a different physical volume to the message journal or paging directory.
Any message larger than a certain size is considered a large message. Large messages
will be split up and sent in fragments. This is determined by the parameter min-large-message-size
The default value is 100KiB.
If the HornetQ Core API is used, the minimal large message size is specified by
ClientSessionFactory.setMinLargeMessageSize
.
ServerLocator locator = HornetQClient.createServerLocatorWithoutHA(new TransportConfiguration(NettyConnectorFactory.class.getName())) locator.setMinLargeMessageSize(25 * 1024); ClientSessionFactory factory = HornetQClient.createClientSessionFactory();
Section 16.3, “Configuring the transport directly from the client side.” will provide more information on how to instantiate the session factory.
If JNDI is used to look up the connection factory, the minimum large message size
is specified in hornetq-jms.xml
... <connection-factory name="ConnectionFactory"> <connectors> <connector-ref connector-name="netty"/> </connectors> <entries> <entry name="ConnectionFactory"/> <entry name="XAConnectionFactory"/> </entries> <min-large-message-size>250000</min-large-message-size> </connection-factory> ...
If the connection factory is being instantiated directly, the minimum large
message size is specified by HornetQConnectionFactory.setMinLargeMessageSize
.
If you specify the boolean property compress-large-message
on
the server locator
or ConnectionFactory
The
system will use the ZIP algorithm to compress the message body as the message is
transfered to the server's side. Notice that there's no special treatment at the
server's side, all the compressing and uncompressing is done at the client.
HornetQ supports setting the body of messages using input and output streams (java.lang.io
)
These streams are then used directly for sending (input streams) and receiving (output streams) messages.
When receiving messages there are 2 ways to deal with the output stream; you may
choose to block while the output stream is recovered using the method ClientMessage.saveOutputStream
or alternatively using the method ClientMessage.setOutputstream
which will asynchronously write the message
to the stream. If you choose the latter the consumer must be kept alive until the
message has been fully received.
You can use any kind of stream you like. The most common use case is to send files
stored in your disk, but you could also send things like JDBC Blobs, SocketInputStream
, things you recovered from HTTPRequests
etc. Anything as long as it implements java.io.InputStream
for sending messages or java.io.OutputStream
for receiving them.
The following table shows a list of methods available at ClientMessage
which are also available through JMS by the use of
object properties.
Table 23.1. org.hornetq.api.core.client.ClientMessage API
Name | Description | JMS Equivalent Property |
---|---|---|
setBodyInputStream(InputStream) | Set the InputStream used to read a message body when sending it. | JMS_HQ_InputStream |
setOutputStream(OutputStream) | Set the OutputStream that will receive the body of a message. This method does not block. | JMS_HQ_OutputStream |
saveOutputStream(OutputStream) | Save the body of the message to the OutputStream . It will block until the entire content
is transferred to the OutputStream . | JMS_HQ_SaveStream |
To set the output stream when receiving a core message:
... ClientMessage msg = consumer.receive(...); // This will block here until the stream was transferred msg.saveOutputStream(someOutputStream); ClientMessage msg2 = consumer.receive(...); // This will not wait the transfer to finish msg.setOutputStream(someOtherOutputStream); ...
Set the input stream when sending a core message:
... ClientMessage msg = session.createMessage(); msg.setInputStream(dataInputStream); ...
Notice also that for messages with more than 2GiB the getBodySize() will return invalid values since this is an integer (which is also exposed to the JMS API). On those cases you can use the message property _HQ_LARGE_SIZE.
When using JMS, HornetQ maps the streaming methods on the core API (see Table 23.1, “org.hornetq.api.core.client.ClientMessage API”) by setting object properties . You
can use the method Message.setObjectProperty
to set the input and
output streams.
The InputStream
can be defined through the JMS Object Property
JMS_HQ_InputStream on messages being sent:
BytesMessage message = session.createBytesMessage(); FileInputStream fileInputStream = new FileInputStream(fileInput); BufferedInputStream bufferedInput = new BufferedInputStream(fileInputStream); message.setObjectProperty("JMS_HQ_InputStream", bufferedInput); someProducer.send(message);
The OutputStream
can be set through the JMS Object Property
JMS_HQ_SaveStream on messages being received in a blocking way.
BytesMessage messageReceived = (BytesMessage)messageConsumer.receive(120000); File outputFile = new File("huge_message_received.dat"); FileOutputStream fileOutputStream = new FileOutputStream(outputFile); BufferedOutputStream bufferedOutput = new BufferedOutputStream(fileOutputStream); // This will block until the entire content is saved on disk messageReceived.setObjectProperty("JMS_HQ_SaveStream", bufferedOutput);
Setting the OutputStream
could also be done in a non blocking
way using the property JMS_HQ_OutputStream.
// This won't wait the stream to finish. You need to keep the consumer active. messageReceived.setObjectProperty("JMS_HQ_OutputStream", bufferedOutput);
When using JMS, Streaming large messages are only supported on StreamMessage
and BytesMessage
.
If you choose not to use the InputStream
or OutputStream
capability of HornetQ You could still access the data
directly in an alternative fashion.
On the Core API just get the bytes of the body as you normally would.
ClientMessage msg = consumer.receive(); byte[] bytes = new byte[1024]; for (int i = 0 ; i < msg.getBodySize(); i += bytes.length) { msg.getBody().readBytes(bytes); // Whatever you want to do with the bytes }
If using JMS API, BytesMessage
and StreamMessage
also supports it transparently.
BytesMessage rm = (BytesMessage)cons.receive(10000); byte data[] = new byte[1024]; for (int i = 0; i < rm.getBodyLength(); i += 1024) { int numberOfBytes = rm.readBytes(data); // Do whatever you want with the data }
Please see Section 11.1.30, “Large Message” for an example which shows how large message is configured and used with JMS.
HornetQ transparently supports huge queues containing millions of messages while the server is running with limited memory.
In such a situation it's not possible to store all of the queues in memory at any one time, so HornetQ transparently pages messages into and out of memory as they are needed, thus allowing massive queues with a low memory footprint.
HornetQ will start paging messages to disk, when the size of all messages in memory for an address exceeds a configured maximum size.
By default, HornetQ does not page messages - this must be explicitly configured to activate it.
Messages are stored per address on the file system. Each address has an individual
folder where messages are stored in multiple files (page files). Each file will contain
messages up to a max configured size (page-size-bytes
). The system
will navigate on the files as needed, and it will remove the page file as soon as all
the messages are acknowledged up to that point.
Browsers will read through the page-cursor system.
Consumers with selectors will also navigate through the page-files and it will ignore messages that don't match the criteria.
You can configure the location of the paging folder
Global paging parameters are specified on the main configuration file (hornetq-configuration.xml
).
<configuration xmlns="urn:hornetq" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="urn:hornetq /schema/hornetq-configuration.xsd"> ... <paging-directory>/somewhere/paging-directory</paging-directory> ...
Table 24.1. Paging Configuration Parameters
Property Name | Description | Default |
---|---|---|
paging-directory | Where page files are stored. HornetQ will create one folder for each address being paged under this configured location. | data/paging |
As soon as messages delivered to an address exceed the configured size, that address alone goes into page mode.
Paging is done individually per address. If you configure a max-size-bytes for an address, that means each matching address will have a maximum size that you specified. It DOES NOT mean that the total overall size of all matching addresses is limited to max-size-bytes.
Configuration is done at the address settings, done at the main configuration file
(hornetq-configuration.xml
).
<address-settings> <address-setting match="jms.someaddress"> <max-size-bytes>104857600</max-size-bytes> <page-size-bytes>10485760</page-size-bytes> <address-full-policy>PAGE</address-full-policy> </address-setting> </address-settings>
This is the list of available parameters on the address settings.
Table 24.2. Paging Address Settings
Property Name | Description | Default |
---|---|---|
max-size-bytes | What's the max memory the address could have before entering on page mode. | -1 (disabled) |
page-size-bytes | The size of each page file used on the paging system | 10MiB (10 * 1024 * 1024 bytes) |
address-full-policy | This must be set to PAGE for paging to enable. If the value is PAGE then further messages will be paged to disk. If the value is DROP then further messages will be silently dropped. If the value is FAIL then the messages will be dropped and the client message producers will receive an exception. If the value is BLOCK then client message producers will block when they try and send further messages. | PAGE |
page-max-cache-size | The system will keep up to <page-max-cache-size page files in memory to
optimize IO during paging navigation. | 5 |
Instead of paging messages when the max size is reached, an address can also be configured to just drop messages when the address is full.
To do this just set the address-full-policy
to DROP
in the address settings
Instead of paging messages when the max size is reached, an address can also be configured to drop messages and also throw an exception on the client-side when the address is full.
To do this just set the address-full-policy
to FAIL
in the address settings
Instead of paging messages when the max size is reached, an address can also be configured to block producers from sending further messages when the address is full, thus preventing the memory being exhausted on the server.
When memory is freed up on the server, producers will automatically unblock and be able to continue sending.
To do this just set the address-full-policy
to BLOCK
in the address settings
In the default configuration, all addresses are configured to block producers after 10 MiB of data are in the address.
When a message is routed to an address that has multiple queues bound to it, e.g. a JMS subscription in a Topic, there is only 1 copy of the message in memory. Each queue only deals with a reference to this. Because of this the memory is only freed up once all queues referencing the message have delivered it.
If you have a single lazy subscription, the entire address will suffer IO performance hit as all the queues will have messages being sent through an extra storage on the paging system.
For example:
An address has 10 queues
One of the queues does not deliver its messages (maybe because of a slow consumer).
Messages continually arrive at the address and paging is started.
The other 9 queues are empty even though messages have been sent.
In this example all the other 9 queues will be consuming messages from the page system. This may cause performance issues if this is an undesirable state.
See Section 11.1.42, “Paging” for an example which shows how to use paging with HornetQ.
Queue attributes can be set in one of two ways. Either by configuring them using the configuration file or by using the core API. This chapter will explain how to configure each attribute and what effect the attribute has.
Queues can be predefined via configuration at a core level or at a JMS level. Firstly lets look at a JMS level.
The following shows a queue predefined in the hornetq-jms.xml
configuration file.
<queue name="selectorQueue"> <entry name="/queue/selectorQueue"/> <selector string="color='red'"/> <durable>true</durable> </queue>
This name attribute of queue defines the name of the queue. When we do this at a jms
level we follow a naming convention so the actual name of the core queue will be
jms.queue.selectorQueue
.
The entry element configures the name that will be used to bind the queue to JNDI. This is a mandatory element and the queue can contain multiple of these to bind the same queue to different names.
The selector element defines what JMS message selector the predefined queue will have. Only messages that match the selector will be added to the queue. This is an optional element with a default of null when omitted.
The durable element specifies whether the queue will be persisted. This again is optional and defaults to true if omitted.
Secondly a queue can be predefined at a core level in the hornetq-configuration.xml
file. The following is an example.
<queues> <queue name="jms.queue.selectorQueue"> <address>jms.queue.selectorQueue</address> <filter string="color='red'"/> <durable>true</durable> </queue> </queues>
This is very similar to the JMS configuration, with 3 real differences which are.
The name attribute of queue is the actual name used for the queue with no naming convention as in JMS.
The address element defines what address is used for routing messages.
There is no entry element.
The filter uses the Core filter syntax (described in Chapter 14, Filter Expressions), not the JMS selector syntax.
Queues can also be created using the core API or the management API.
For the core API, queues can be created via the org.hornetq.api.core.client.ClientSession
interface. There are multiple
createQueue
methods that support setting all of the previously
mentioned attributes. There is one extra attribute that can be set via this API which is
temporary
. setting this to true means that the queue will be
deleted once the session is disconnected.
Take a look at Chapter 30, Management for a description of the management API for creating queues.
There are some attributes that are defined against an address wildcard rather than a
specific queue. Here an example of an address-setting
entry that
would be found in the hornetq-configuration.xml
file.
<address-settings> <address-setting match="jms.queue.exampleQueue"> <dead-letter-address>jms.queue.deadLetterQueue</dead-letter-address> <max-delivery-attempts>3</max-delivery-attempts> <redelivery-delay>5000</redelivery-delay> <expiry-address>jms.queue.expiryQueue</expiry-address> <last-value-queue>true</last-value-queue> <max-size-bytes>100000</max-size-bytes> <page-size-bytes>20000</page-size-bytes> <redistribution-delay>0</redistribution-delay> <send-to-dla-on-no-route>true</send-to-dla-on-no-route> <address-full-policy>PAGE</address-full-policy> </address-setting> </address-settings>
The idea with address settings, is you can provide a block of settings which will be
applied against any adresses that match the string in the match
attribute. In the
above example the settings would only be applied to any addresses which exactly match
the address jms.queue.exampleQueue
, but you can also use wildcards to apply sets of
configuration against many addresses. The wildcard syntax used is described here.
For example, if you used the match
string jms.queue.#
the settings would be applied
to all addresses which start with jms.queue.
which would be all JMS queues.
The meaning of the specific settings are explained fully throughout the user manual, however here is a brief description with a link to the appropriate chapter if available.
max-delivery-attempts
defines how many time a cancelled message can
be redelivered before sending to the dead-letter-address
. A full
explanation can be found here.
redelivery-delay
defines how long to wait before attempting
redelivery of a cancelled message. see here.
expiry-address
defines where to send a message that has expired.
see here.
expiry-delay
defines the expiration time that will be used for messages which are using
the default expiration time (i.e. 0). For example, if expiry-delay
is set to "10" and a
message which is using the default expiration time (i.e. 0) arrives then its expiration time of "0" will be
changed to "10." However, if a message which is using an expiration time of "20" arrives then its expiration
time will remain unchanged. Setting expiry-delay
to "-1" will disable this feature. The
default is "-1".
last-value-queue
defines whether a queue only uses last values or
not. see here.
max-size-bytes
and page-size-bytes
are used to
set paging on an address. This is explained here.
redistribution-delay
defines how long to wait when the last
consumer is closed on a queue before redistributing any messages. see here.
send-to-dla-on-no-route
. If a message is sent to an address, but the server does not route it to any queues,
for example, there might be no queues bound to that address, or none of the queues have filters that match, then normally that message
would be discarded. However if this parameter is set to true for that address, if the message is not routed to any queues it will instead
be sent to the dead letter address (DLA) for that address, if it exists.
address-full-policy
. This attribute can have one of the following values: PAGE, DROP, FAIL or BLOCK and determines what happens when
an address where max-size-bytes
is specified becomes full. The default value is PAGE. If the value is PAGE then further messages will be paged to disk.
If the value is DROP then further messages will be silently dropped.
If the value is FAIL then further messages will be dropped and an exception will be thrown on the client-side.
If the value is BLOCK then client message producers will block when they try and send further messages.
See the following chapters for more info Chapter 19, Flow Control, Chapter 24, Paging.
Scheduled messages differ from normal messages in that they won't be delivered until a specified time in the future, at the earliest.
To do this, a special property is set on the message before sending it.
The property name used to identify a scheduled message is "_HQ_SCHED_DELIVERY"
(or the constant Message.HDR_SCHEDULED_DELIVERY_TIME
).
The specified value must be a positive long
corresponding to the time the
message must be delivered (in milliseconds). An example of sending a scheduled message
using the JMS API is as follows.
TextMessage message = session.createTextMessage("This is a scheduled message message which will be delivered in 5 sec."); message.setLongProperty("_HQ_SCHED_DELIVERY", System.currentTimeMillis() + 5000); producer.send(message); ... // message will not be received immediately but 5 seconds later TextMessage messageReceived = (TextMessage) consumer.receive();
Scheduled messages can also be sent using the core API, by setting the same property on the core message before sending.
See Section 11.1.51, “Scheduled Message” for an example which shows how scheduled messages can be used with JMS.
Last-Value queues are special queues which discard any messages when a newer message with the same value for a well-defined Last-Value property is put in the queue. In other words, a Last-Value queue only retains the last value.
A typical example for Last-Value queue is for stock prices, where you are only interested by the latest value for a particular stock.
Last-value queues are defined in the address-setting configuration:
<address-setting match="jms.queue.lastValueQueue"> <last-value-queue>true</last-value-queue> </address-setting>
By default, last-value-queue
is false. Address wildcards can be used
to configure Last-Value queues for a set of addresses (see Chapter 13, Understanding the HornetQ Wildcard Syntax).
The property name used to identify the last value is "_HQ_LVQ_NAME"
(or the constant Message.HDR_LAST_VALUE_NAME
from the Core API).
For example, if two messages with the same value for the Last-Value property are sent to a Last-Value queue, only the latest message will be kept in the queue:
// send 1st message with Last-Value property set to STOCK_NAME TextMessage message = session.createTextMessage("1st message with Last-Value property set"); message.setStringProperty("_HQ_LVQ_NAME", "STOCK_NAME"); producer.send(message); // send 2nd message with Last-Value property set to STOCK_NAME message = session.createTextMessage("2nd message with Last-Value property set"); message.setStringProperty("_HQ_LVQ_NAME", "STOCK_NAME"); producer.send(message); ... // only the 2nd message will be received: it is the latest with // the Last-Value property set TextMessage messageReceived = (TextMessage)messageConsumer.receive(5000); System.out.format("Received message: %s\n", messageReceived.getText());
See Section 11.1.31, “Last-Value Queue” for an example which shows how last value queues are configured and used with JMS.
Message groups are sets of messages that have the following characteristics:
Messages in a message group share the same group id, i.e. they have same group
identifier property (JMSXGroupID
for JMS, _HQ_GROUP_ID
for HornetQ Core API).
Messages in a message group are always consumed by the same consumer, even if there are many consumers on a queue. They pin all messages with the same group id to the same consumer. If that consumer closes another consumer is chosen and will receive all messages with the same group id.
Message groups are useful when you want all messages for a certain value of the property to be processed serially by the same consumer.
An example might be orders for a certain stock. You may want orders for any particular stock to be processed serially by the same consumer. To do this you can create a pool of consumers (perhaps one for each stock, but less will work too), then set the stock name as the value of the _HQ_GROUP_ID property.
This will ensure that all messages for a particular stock will always be processed by the same consumer.
The property name used to identify the message group is "_HQ_GROUP_ID"
(or the constant MessageImpl.HDR_GROUP_ID
). Alternatively, you can set autogroup
to true on the SessionFactory
which will pick a
random unique id.
The property name used to identify the message group is JMSXGroupID
.
// send 2 messages in the same group to ensure the same // consumer will receive both Message message = ... message.setStringProperty("JMSXGroupID", "Group-0"); producer.send(message); message = ... message.setStringProperty("JMSXGroupID", "Group-0"); producer.send(message);
Alternatively, you can set autogroup
to true on the HornetQConnectonFactory
which will pick a random unique id. This can also be
set in the hornetq-jms.xml
file like this:
<connection-factory name="ConnectionFactory"> <connectors> <connector-ref connector-name="netty-connector"/> </connectors> <entries> <entry name="ConnectionFactory"/> </entries> <autogroup>true</autogroup> </connection-factory>
Alternatively you can set the group id via the connection factory. All messages sent
with producers created via this connection factory will set the JMSXGroupID
to the specified value on all messages sent. To configure the
group id set it on the connection factory in the hornetq-jms.xml
config
file as follows
<connection-factory name="ConnectionFactory"> <connectors> <connector-ref connector-name="netty-connector"/> </connectors> <entries> <entry name="ConnectionFactory"/> </entries> <group-id>Group-0</group-id> </connection-factory>
See Section 11.1.35, “Message Group” for an example which shows how message groups are configured and used with JMS.
See Section 11.1.36, “Message Group” for an example which shows how message groups are configured via a connection factory.
Using message groups in a cluster is a bit more complex. This is because messages with a particular group id can arrive on any node so each node needs to know about which group id's are bound to which consumer on which node. The consumer handling messages for a particular group id may be on a different node of the cluster, so each node needs to know this information so it can route the message correctly to the node which has that consumer.
To solve this there is the notion of a grouping handler. Each node will have its own grouping handler and when a messages is sent with a group id assigned, the handlers will decide between them which route the message should take.
There are 2 types of handlers; Local and Remote. Each cluster should choose 1 node to have a local grouping handler and all the other nodes should have remote handlers- it's the local handler that actually makes the decsion as to what route should be used, all the other remote handlers converse with this. Here is a sample config for both types of handler, this should be configured in the hornetq-configuration.xml file.
<grouping-handler name="my-grouping-handler"> <type>LOCAL</type> <address>jms</address> <timeout>5000</timeout> </grouping-handler> <grouping-handler name="my-grouping-handler"> <type>REMOTE</type> <address>jms</address> <timeout>5000</timeout> </grouping-handler>
The address attribute refers to a cluster connection and the address it uses, refer to the clustering section on how to configure clusters. The timeout attribute referes to how long to wait for a decision to be made, an exception will be thrown during the send if this timeout is reached, this ensures that strict ordering is kept.
The decision as to where a message should be routed to is initially proposed by the node that receives the message. The node will pick a suitable route as per the normal clustered routing conditions, i.e. round robin available queues, use a local queue first and choose a queue that has a consumer. If the proposal is accepted by the grouping handlers the node will route messages to this queue from that point on, if rejected an alternative route will be offered and the node will again route to that queue indefinitely. All other nodes will also route to the queue chosen at proposal time. Once the message arrives at the queue then normal single server message group semantics take over and the message is pinned to a consumer on that queue.
You may have noticed that there is a single point of failure with the single local handler. If this node crashes then no decisions will be able to be made. Any messages sent will be not be delivered and an exception thrown. To avoid this happening Local Handlers can be replicated on another backup node. Simple create your back up node and configure it with the same Local handler.
Some best practices should be followed when using clustered grouping:
Make sure your consumers are distributed evenly across the different nodes if possible. This is only an issue if you are creating and closing consumers regularly. Since messages are always routed to the same queue once pinned, removing a consumer from this queue may leave it with no consumers meaning the queue will just keep receiving the messages. Avoid closing consumers or make sure that you always have plenty of consumers, i.e., if you have 3 nodes have 3 consumers.
Use durable queues if possible. If queues are removed once a group is bound to it, then it is possible that other nodes may still try to route messages to it. This can be avoided by making sure that the queue is deleted by the session that is sending the messages. This means that when the next message is sent it is sent to the node where the queue was deleted meaning a new proposal can succesfully take place. Alternatively you could just start using a different group id.
Always make sure that the node that has the Local Grouping Handler is replicated. These means that on failover grouping will still occur.
See Section 11.1.8, “Clustered Grouping” for an example of how to configure message groups with a HornetQ cluster
JMS specifies 3 acknowledgement modes:
AUTO_ACKNOWLEDGE
CLIENT_ACKNOWLEDGE
DUPS_OK_ACKNOWLEDGE
HornetQ supports two additional modes: PRE_ACKNOWLEDGE
and INDIVIDUAL_ACKNOWLEDGE
In some cases you can afford to lose messages in event of failure, so it would make sense to acknowledge the message on the server before delivering it to the client.
This extra mode is supported by HornetQ and will call it pre-acknowledge mode.
The disadvantage of acknowledging on the server before delivery is that the message will be lost if the system crashes after acknowledging the message on the server but before it is delivered to the client. In that case, the message is lost and will not be recovered when the system restart.
Depending on your messaging case, pre-acknowledgement
mode can avoid
extra network traffic and CPU at the cost of coping with message loss.
An example of a use case for pre-acknowledgement is for stock price update messages. With these messages it might be reasonable to lose a message in event of crash, since the next price update message will arrive soon, overriding the previous price.
Please note, that if you use pre-acknowledge mode, then you will lose transactional semantics for messages being consumed, since clearly they are being acknowledged first on the server, not when you commit the transaction. This may be stating the obvious but we like to be clear on these things to avoid confusion!
This can be configured in the hornetq-jms.xml
file on the connection factory
like this:
<connection-factory name="ConnectionFactory"> <connectors> <connector-ref connector-name="netty-connector"/> </connectors> <entries> <entry name="ConnectionFactory"/> </entries> <pre-acknowledge>true</pre-acknowledge> </connection-factory>
Alternatively, to use pre-acknowledgement mode using the JMS API, create a JMS Session
with the HornetQSession.PRE_ACKNOWLEDGE
constant.
// messages will be acknowledge on the server *before* being delivered to the client Session session = connection.createSession(false, HornetQJMSConstants.PRE_ACKNOWLEDGE);
Or you can set pre-acknowledge directly on the HornetQConnectionFactory
instance using the setter method.
To use pre-acknowledgement mode using the core API you can set it directly on the
ClientSessionFactory
instance using the setter method.
A valid usecase for individual acknowledgement would be when you need to have your own scheduling and you don't know when your message processing will be finished. You should prefer having one consumer per thread worker but this is not possible in some circunstances depending on how complex is your processing. For that you can use the individual Acknowledgement.
You basically setup Individual ACK by creating a session with the acknowledge mode with HornetQJMSConstants.INDIVIDUAL_ACKNOWLEDGE
. Individual ACK inherits all the semantics from Client Acknowledge,
with the exception the message is individually acked.
Please note, that to avoid confusion on MDB processing, Individual ACKNOWLEDGE is not supported through MDBs (or the inbound resource adapter). this is because you have to finish the process of your message inside the MDB.
See Section 11.1.43, “Pre-Acknowledge” for an example which shows how to use pre-acknowledgement mode with JMS.
HornetQ has an extensive management API that allows a user to modify a server configuration, create new resources (e.g. JMS queues and topics), inspect these resources (e.g. how many messages are currently held in a queue) and interact with it (e.g. to remove messages from a queue). All the operations allows a client to manage HornetQ. It also allows clients to subscribe to management notifications.
There are 3 ways to manage HornetQ:
Using JMX -- JMX is the standard way to manage Java applications
Using the core API -- management operations are sent to HornetQ server using core messages
Using the JMS API -- management operations are sent to HornetQ server using JMS messages
Although there are 3 different ways to manage HornetQ each API supports the same functionality. If it is possible to manage a resource using JMX it is also possible to achieve the same result using Core messages or JMS messages.
This choice depends on your requirements, your application settings and your environment to decide which way suits you best.
Regardless of the way you invoke management operations, the management API is the same.
For each managed resource, there exists a Java interface describing what can be invoked for this type of resource.
HornetQ exposes its managed resources in 2 packages:
Core resources are located in the org.hornetq.api.core.management
package
JMS resources are located in the org.hornetq.api.jms.management
package
The way to invoke a management operations depends whether JMX, core messages, or JMS messages are used.
A few management operations requires a filter
parameter to chose
which messages are involved by the operation. Passing null
or an
empty string means that the management operation will be performed on all
messages.
HornetQ defines a core management API to manage core resources. For full details of the API please consult the javadoc. In summary:
Listing, creating, deploying and destroying queues
A list of deployed core queues can be retrieved using the getQueueNames()
method.
Core queues can be created or destroyed using the management operations
createQueue()
or deployQueue()
or
destroyQueue()
)on the HornetQServerControl
(with the ObjectName org.hornetq:module=Core,type=Server
or the resource name core.server
)
createQueue
will fail if the queue already exists while
deployQueue
will do nothing.
Pausing and resuming Queues
The QueueControl
can pause and resume the underlying
queue. When a queue is paused, it will receive messages but will not deliver
them. When it's resumed, it'll begin delivering the queued messages, if any.
Listing and closing remote connections
Client's remote addresses can be retrieved using listRemoteAddresses()
. It is also possible to close the
connections associated with a remote address using the closeConnectionsForAddress()
method.
Alternatively, connection IDs can be listed using listConnectionIDs()
and all the sessions for a given connection
ID can be listed using listSessions()
.
Transaction heuristic operations
In case of a server crash, when the server restarts, it it possible that
some transaction requires manual intervention. The listPreparedTransactions()
method lists the transactions which
are in the prepared states (the transactions are represented as opaque Base64
Strings.) To commit or rollback a given prepared transaction, the commitPreparedTransaction()
or rollbackPreparedTransaction()
method can be used to resolve
heuristic transactions. Heuristically completed transactions can be listed
using the listHeuristicCommittedTransactions()
and listHeuristicRolledBackTransactions
methods.
Enabling and resetting Message counters
Message counters can be enabled or disabled using the enableMessageCounters()
or disableMessageCounters()
method. To reset message counters, it is
possible to invoke resetAllMessageCounters()
and resetAllMessageCounterHistories()
methods.
Retrieving the server configuration and attributes
The HornetQServerControl
exposes HornetQ server
configuration through all its attributes (e.g. getVersion()
method to retrieve the server's version, etc.)
Listing, creating and destroying Core bridges and diverts
A list of deployed core bridges (resp. diverts) can be retrieved using the getBridgeNames()
(resp. getDivertNames()
) method.
Core bridges (resp. diverts) can be created or destroyed using the management operations
createBridge()
and destroyBridge()
(resp. createDivert()
and destroyDivert()
) on the HornetQServerControl
(with the ObjectName org.hornetq:module=Core,type=Server
or the resource name core.server
).
It is possible to stop the server and force failover to occur with any currently attached clients.
to do this use the forceFailover()
on the HornetQServerControl
(with the ObjectName org.hornetq:module=Core,type=Server
or the resource name core.server
)
Core addresses can be managed using the AddressControl
class
(with the ObjectName org.hornetq:module=Core,type=Address,name="<the
address name>"
or the resource name core.address.<the
address name>
).
Modifying roles and permissions for an address
You can add or remove roles associated to a queue using the addRole()
or removeRole()
methods. You can
list all the roles associated to the queue with the getRoles()
method
The bulk of the core management API deals with core queues. The QueueControl
class defines the Core queue management operations (with
the ObjectName org.hornetq:module=Core,type=Queue,address="<the bound
address>",name="<the queue name>"
or the resource name core.queue.<the queue name>
).
Most of the management operations on queues take either a single message ID (e.g. to remove a single message) or a filter (e.g. to expire all messages with a given property.)
Expiring, sending to a dead letter address and moving messages
Messages can be expired from a queue by using the expireMessages()
method. If an expiry address is defined,
messages will be sent to it, otherwise they are discarded. The queue's
expiry address can be set with the setExpiryAddress()
method.
Messages can also be sent to a dead letter address with the sendMessagesToDeadLetterAddress()
method. It returns the number
of messages which are sent to the dead letter address. If a dead letter address
is not defined, message are removed from the queue and discarded. The queue's
dead letter address can be set with the setDeadLetterAddress()
method.
Messages can also be moved from a queue to another queue by using the
moveMessages()
method.
Listing and removing messages
Messages can be listed from a queue by using the listMessages()
method which returns an array of Map
, one Map
for each message.
Messages can also be removed from the queue by using the removeMessages()
method which returns a boolean
for the single message ID variant or the number of
removed messages for the filter variant. The removeMessages()
method takes a filter
argument to remove only filtered messages. Setting the filter to an empty
string will in effect remove all messages.
Counting messages
The number of messages in a queue is returned by the getMessageCount()
method. Alternatively, the countMessages()
will return the number of messages in the queue
which match a given filter
Changing message priority
The message priority can be changed by using the changeMessagesPriority()
method which returns a boolean
for the single message ID variant or the number of
updated messages for the filter variant.
Message counters
Message counters can be listed for a queue with the listMessageCounter()
and listMessageCounterHistory()
methods (see Section 30.6, “Message Counters”). The message counters can also be
reset for a single queue using the resetMessageCounter()
method.
Retrieving the queue attributes
The QueueControl
exposes Core queue settings through its
attributes (e.g. getFilter()
to retrieve the queue's filter
if it was created with one, isDurable()
to know whether the
queue is durable or not, etc.)
Pausing and resuming Queues
The QueueControl
can pause and resume the underlying
queue. When a queue is paused, it will receive messages but will not deliver
them. When it's resume, it'll begin delivering the queued messages, if any.
HornetQ allows to start and stop its remote resources (acceptors, diverts, bridges, etc.) so that a server can be taken off line for a given period of time without stopping it completely (e.g. if other management operations must be performed such as resolving heuristic transactions). These resources are:
Acceptors
They can be started or stopped using the start()
or.
stop()
method on the AcceptorControl
class (with the ObjectName org.hornetq:module=Core,type=Acceptor,name="<the acceptor
name>"
or the resource name core.acceptor.<the
address name>
). The acceptors parameters can be retrieved using
the AcceptorControl
attributes (see Section 16.1, “Understanding Acceptors”)
Diverts
They can be started or stopped using the start()
or
stop()
method on the DivertControl
class (with the ObjectName org.hornetq:module=Core,type=Divert,name=<the divert name>
or the resource name core.divert.<the divert name>
).
Diverts parameters can be retrieved using the DivertControl
attributes (see Chapter 35, Diverting and Splitting Message Flows)
Bridges
They can be started or stopped using the start()
(resp.
stop()
) method on the BridgeControl
class (with the ObjectName org.hornetq:module=Core,type=Bridge,name="<the bridge
name>"
or the resource name core.bridge.<the bridge
name>
). Bridges parameters can be retrieved using the BridgeControl
attributes (see Chapter 36, Core Bridges)
Broadcast groups
They can be started or stopped using the start()
or
stop()
method on the BroadcastGroupControl
class (with the ObjectName org.hornetq:module=Core,type=BroadcastGroup,name="<the broadcast group
name>"
or the resource name core.broadcastgroup.<the broadcast group name>
). Broadcast
groups parameters can be retrieved using the BroadcastGroupControl
attributes (see Chapter 38, Clusters)
Discovery groups
They can be started or stopped using the start()
or
stop()
method on the DiscoveryGroupControl
class (with the ObjectName org.hornetq:module=Core,type=DiscoveryGroup,name="<the discovery group
name>"
or the resource name core.discovery.<the
discovery group name>
). Discovery groups parameters can be
retrieved using the DiscoveryGroupControl
attributes (see
Chapter 38, Clusters)
Cluster connections
They can be started or stopped using the start()
or
stop()
method on the ClusterConnectionControl
class (with the ObjectName org.hornetq:module=Core,type=ClusterConnection,name="<the cluster
connection name>"
or the resource name core.clusterconnection.<the cluster connection name>
).
Cluster connections parameters can be retrieved using the ClusterConnectionControl
attributes (see Chapter 38, Clusters)
HornetQ defines a JMS Management API to manage JMS administrated objects (i.e. JMS queues, topics and connection factories).
JMS Resources (connection factories and destinations) can be created using the
JMSServerControl
class (with the ObjectName org.hornetq:module=JMS,type=Server
or the resource name jms.server
).
Listing, creating, destroying connection factories
Names of the deployed connection factories can be retrieved by the getConnectionFactoryNames()
method.
JMS connection factories can be created or destroyed using the createConnectionFactory()
methods or destroyConnectionFactory()
methods. These connection factories
are bound to JNDI so that JMS clients can look them up. If a graphical console
is used to create the connection factories, the transport parameters are
specified in the text field input as a comma-separated list of key=value (e.g.
key1=10, key2="value", key3=false
). If there are multiple
transports defined, you need to enclose the key/value pairs between curly
braces. For example {key=10}, {key=20}
. In that case, the
first key
will be associated to the first transport
configuration and the second key
will be associated to the
second transport configuration (see Chapter 16, Configuring the Transport
for a list of the transport parameters)
Listing, creating, destroying queues
Names of the deployed JMS queues can be retrieved by the getQueueNames()
method.
JMS queues can be created or destroyed using the createQueue()
methods or destroyQueue()
methods. These queues are bound to JNDI so that JMS clients can look them
up
Listing, creating/destroying topics
Names of the deployed topics can be retrieved by the getTopicNames()
method.
JMS topics can be created or destroyed using the createTopic()
or destroyTopic()
methods. These
topics are bound to JNDI so that JMS clients can look them up
Listing and closing remote connections
JMS Clients remote addresses can be retrieved using listRemoteAddresses()
. It is also possible to close the
connections associated with a remote address using the closeConnectionsForAddress()
method.
Alternatively, connection IDs can be listed using listConnectionIDs()
and all the sessions for a given connection
ID can be listed using listSessions()
.
JMS Connection Factories can be managed using the ConnectionFactoryControl
class (with the ObjectName org.hornetq:module=JMS,type=ConnectionFactory,name="<the connection factory
name>"
or the resource name jms.connectionfactory.<the
connection factory name>
).
Retrieving connection factory attributes
The ConnectionFactoryControl
exposes JMS
ConnectionFactory configuration through its attributes (e.g. getConsumerWindowSize()
to retrieve the consumer window size for
flow control, isBlockOnNonDurableSend()
to know whether the
producers created from the connection factory will block or not when sending
non-durable messages, etc.)
JMS queues can be managed using the JMSQueueControl
class (with
the ObjectName org.hornetq:module=JMS,type=Queue,name="<the queue
name>"
or the resource name jms.queue.<the queue
name>
).
The management operations on a JMS queue are very similar to the operations on a core queue.
Expiring, sending to a dead letter address and moving messages
Messages can be expired from a queue by using the expireMessages()
method. If an expiry address is defined,
messages will be sent to it, otherwise they are discarded. The queue's
expiry address can be set with the setExpiryAddress()
method.
Messages can also be sent to a dead letter address with the sendMessagesToDeadLetterAddress()
method. It returns the number
of messages which are sent to the dead letter address. If a dead letter address
is not defined, message are removed from the queue and discarded. The queue's
dead letter address can be set with the setDeadLetterAddress()
method.
Messages can also be moved from a queue to another queue by using the
moveMessages()
method.
Listing and removing messages
Messages can be listed from a queue by using the listMessages()
method which returns an array of Map
, one Map
for each message.
Messages can also be removed from the queue by using the removeMessages()
method which returns a boolean
for the single message ID variant or the number of
removed messages for the filter variant. The removeMessages()
method takes a filter
argument to remove only filtered messages. Setting the filter to an empty
string will in effect remove all messages.
Counting messages
The number of messages in a queue is returned by the getMessageCount()
method. Alternatively, the countMessages()
will return the number of messages in the queue
which match a given filter
Changing message priority
The message priority can be changed by using the changeMessagesPriority()
method which returns a boolean
for the single message ID variant or the number of
updated messages for the filter variant.
Message counters
Message counters can be listed for a queue with the listMessageCounter()
and listMessageCounterHistory()
methods (see Section 30.6, “Message Counters”)
Retrieving the queue attributes
The JMSQueueControl
exposes JMS queue settings through
its attributes (e.g. isTemporary()
to know whether the queue
is temporary or not, isDurable()
to know whether the queue is
durable or not, etc.)
Pausing and resuming queues
The JMSQueueControl
can pause and resume the underlying
queue. When the queue is paused it will continue to receive messages but will
not deliver them. When resumed again it will deliver the enqueued messages, if
any.
JMS Topics can be managed using the TopicControl
class (with
the ObjectName org.hornetq:module=JMS,type=Topic,name="<the topic
name>"
or the resource name jms.topic.<the topic
name>
).
Listing subscriptions and messages
JMS topics subscriptions can be listed using the listAllSubscriptions()
, listDurableSubscriptions()
, listNonDurableSubscriptions()
methods. These methods return
arrays of Object
representing the subscriptions information
(subscription name, client ID, durability, message count, etc.). It is also
possible to list the JMS messages for a given subscription with the listMessagesForSubscription()
method.
Dropping subscriptions
Durable subscriptions can be dropped from the topic using the dropDurableSubscription()
method.
Counting subscriptions messages
The countMessagesForSubscription()
method can be used to
know the number of messages held for a given subscription (with an optional
message selector to know the number of messages matching the selector)
HornetQ can be managed using JMX.
The management API is exposed by HornetQ using MBeans interfaces. HornetQ registers its
resources with the domain org.hornetq
.
For example, the ObjectName
to manage a JMS Queue exampleQueue
is:
org.hornetq:module=JMS,type=Queue,name="exampleQueue"
and the MBean is:
org.hornetq.api.jms.management.JMSQueueControl
The MBean's ObjectName
are built using the helper class org.hornetq.api.core.management.ObjectNameBuilder
. You can also use jconsole
to find the ObjectName
of the MBeans you want to
manage.
Managing HornetQ using JMX is identical to management of any Java Applications using JMX. It can be done by reflection or by creating proxies of the MBeans.
By default, JMX is enabled to manage HornetQ. It can be disabled by setting jmx-management-enabled
to false
in hornetq-configuration.xml
:
<!-- false to disable JMX management for HornetQ --> <jmx-management-enabled>false</jmx-management-enabled>
If JMX is enabled, HornetQ can be managed locally using jconsole
.
Remote connections to JMX are not enabled by default for security reasons. Please refer
to Java Management guide to configure the server for remote management (system
properties must be set in run.sh
or run.bat
scripts).
By default, HornetQ server uses the JMX domain "org.hornetq". To manage several
HornetQ servers from the same MBeanServer, the JMX domain can be
configured for each individual HornetQ server by setting jmx-domain
in hornetq-configuration.xml
:
<!-- use a specific JMX domain for HornetQ MBeans --> <jmx-domain>my.org.hornetq</jmx-domain>
When HornetQ is run in standalone, it uses the Java Virtual Machine's Platform MBeanServer
to register its MBeans. This is configured in
JBoss Microcontainer Beans file (see Section 6.7, “JBoss Microcontainer Beans File”):
<!-- MBeanServer --> <bean name="MBeanServer" class="javax.management.MBeanServer"> <constructor factoryClass="java.lang.management.ManagementFactory" factoryMethod="getPlatformMBeanServer" /> </bean>
When it is integrated in JBoss AS 5+, it uses the Application Server's own MBean Server so that it can be managed using AS 5's jmx-console:
<!-- MBeanServer --> <bean name="MBeanServer" class="javax.management.MBeanServer"> <constructor factoryClass="org.jboss.mx.util.MBeanServerLocator" factoryMethod="locateJBoss" /> </bean>
See Section 11.1.29, “JMX Management” for an example which shows how to use a remote connection to JMX and MBean proxies to manage HornetQ.
The core management API in HornetQ is called by sending Core messages to a special address, the management address.
Management messages are regular Core messages with well-known properties that the server needs to understand to interact with the management API:
The name of the managed resource
The name of the management operation
The parameters of the management operation
When such a management message is sent to the management address, HornetQ server will
handle it, extract the information, invoke the operation on the managed resources and send
a management reply to the management message's reply-to address
(specified by ClientMessageImpl.REPLYTO_HEADER_NAME
).
A ClientConsumer
can be used to consume the management reply and
retrieve the result of the operation (if any) stored in the reply's body. For portability,
results are returned as a JSON String rather than Java
Serialization (the org.hornetq.api.core.management.ManagementHelper
can
be used to convert the JSON string to Java objects).
These steps can be simplified to make it easier to invoke management operations using Core messages:
Create a ClientRequestor
to send messages to the management
address and receive replies
Create a ClientMessage
Use the helper class org.hornetq.api.core.management.ManagementHelper
to fill the message
with the management properties
Send the message using the ClientRequestor
Use the helper class org.hornetq.api.core.management.ManagementHelper
to retrieve the
operation result from the management reply
For example, to find out the number of messages in the core queue exampleQueue
:
ClientSession session = ... ClientRequestor requestor = new ClientRequestor(session, "jms.queue.hornetq.management"); ClientMessage message = session.createMessage(false); ManagementHelper.putAttribute(message, "core.queue.exampleQueue", "messageCount"); session.start(); ClientMessage reply = requestor.request(m); int count = (Integer) ManagementHelper.getResult(reply); System.out.println("There are " + count + " messages in exampleQueue");
Management operation name and parameters must conform to the Java interfaces defined in
the management
packages.
Names of the resources are built using the helper class org.hornetq.api.core.management.ResourceNames
and are straightforward
(core.queue.exampleQueue
for the Core Queue exampleQueue
, jms.topic.exampleTopic
for the JMS Topic
exampleTopic
, etc.).
The management address to send management messages is configured in hornetq-configuration.xml
:
<management-address>jms.queue.hornetq.management</management-address>
By default, the address is jms.queue.hornetq.management
(it is
prepended by "jms.queue" so that JMS clients can also send management messages).
The management address requires a special user permission
manage
to be able to receive and handle management messages. This
is also configured in hornetq-configuration.xml:
<!-- users with the admin role will be allowed to manage --> <!-- HornetQ using management messages --> <security-setting match="jms.queue.hornetq.management"> <permission type="manage" roles="admin" /> </security-setting>
Using JMS messages to manage HornetQ is very similar to using core API.
An important difference is that JMS requires a JMS queue to send the messages to (instead of an address for the core API).
The management queue is a special queue and needs to be instantiated directly by the client:
Queue managementQueue = HornetQJMSClient.createQueue("hornetq.management");
All the other steps are the same than for the Core API but they use JMS API instead:
create a QueueRequestor
to send messages to the management
address and receive replies
create a Message
use the helper class org.hornetq.api.jms.management.JMSManagementHelper
to fill the message
with the management properties
send the message using the QueueRequestor
use the helper class org.hornetq.api.jms.management.JMSManagementHelper
to retrieve the
operation result from the management reply
For example, to know the number of messages in the JMS queue exampleQueue
:
Queue managementQueue = HornetQJMSClient.createQueue("hornetq.management"); QueueSession session = ... QueueRequestor requestor = new QueueRequestor(session, managementQueue); connection.start(); Message message = session.createMessage(); JMSManagementHelper.putAttribute(message, "jms.queue.exampleQueue", "messageCount"); Message reply = requestor.request(message); int count = (Integer)JMSManagementHelper.getResult(reply); System.out.println("There are " + count + " messages in exampleQueue");
Whether JMS or the core API is used for management, the configuration steps are the same (see Section 30.3.1, “Configuring Core Management”).
See Section 11.1.32, “Management” for an example which shows how to use JMS messages to manage HornetQ server.
HornetQ emits notifications to inform listeners of potentially interesting events (creation of new resources, security violation, etc.).
These notifications can be received by 3 different ways:
JMX notifications
Core messages
JMS messages
If JMX is enabled (see Section 30.2.1, “Configuring JMX”), JMX notifications can be received by subscribing to 2 MBeans:
org.hornetq:module=Core,type=Server
for notifications on
Core resources
org.hornetq:module=JMS,type=Server
for notifications on
JMS resources
HornetQ defines a special management notification address. Core queues can be bound to this address so that clients will receive management notifications as Core messages
A Core client which wants to receive management notifications must create a core queue bound to the management notification address. It can then receive the notifications from its queue.
Notifications messages are regular core messages with additional properties corresponding to the notification (its type, when it occurred, the resources which were concerned, etc.).
Since notifications are regular core messages, it is possible to use message selectors to filter out notifications and receives only a subset of all the notifications emitted by the server.
The management notification address to receive management notifications is
configured in hornetq-configuration.xml
:
<management-notification-address>hornetq.notifications</management-notification-address>
By default, the address is hornetq.notifications
.
HornetQ's notifications can also be received using JMS messages.
It is similar to receiving notifications using Core API but an important difference is that JMS requires a JMS Destination to receive the messages (preferably a Topic).
To use a JMS Destination to receive management notifications, you must change the server's
management notification address to start with jms.queue
if it is a JMS Queue
or jms.topic
if it is a JMS Topic:
<!-- notifications will be consumed from "notificationsTopic" JMS Topic --> <management-notification-address>jms.topic.notificationsTopic</management-notification-address>
Once the notification topic is created, you can receive messages from it or set a
MessageListener
:
Topic notificationsTopic = HornetQJMSClient.createTopic("notificationsTopic"); Session session = ... MessageConsumer notificationConsumer = session.createConsumer(notificationsTopic); notificationConsumer.setMessageListener(new MessageListener() { public void onMessage(Message notif) { System.out.println("------------------------"); System.out.println("Received notification:"); try { Enumeration propertyNames = notif.getPropertyNames(); while (propertyNames.hasMoreElements()) { String propertyName = (String)propertyNames.nextElement(); System.out.format(" %s: %s\n", propertyName, notif.getObjectProperty(propertyName)); } } catch (JMSException e) { } System.out.println("------------------------"); } });
See Section 11.1.33, “Management Notification” for an example which shows
how to use a JMS MessageListener
to receive management notifications
from HornetQ server.
Message counters can be used to obtain information on queues over time as HornetQ keeps a history on queue metrics.
They can be used to show trends on queues. For example, using the management API, it would be possible to query the number of messages in a queue at regular interval. However, this would not be enough to know if the queue is used: the number of messages can remain constant because nobody is sending or receiving messages from the queue or because there are as many messages sent to the queue than messages consumed from it. The number of messages in the queue remains the same in both cases but its use is widely different.
Message counters gives additional information about the queues:
count
The total number of messages added to the queue since the server was started
countDelta
the number of messages added to the queue since the last message counter update
depth
The current number of messages in the queue
depthDelta
The overall number of messages added/removed from the queue
since the last message counter update. For example, if
depthDelta
is equal to -10
this means that
overall 10 messages have been removed from the queue (e.g. 2 messages were added and
12 were removed)
lastAddTimestamp
The timestamp of the last time a message was added to the queue
udpateTimestamp
The timestamp of the last message counter update
By default, message counters are disabled as it might have a small negative effect on memory.
To enable message counters, you can set it to true
in hornetq-configuration.xml
:
<message-counter-enabled>true</message-counter-enabled>
Message counters keeps a history of the queue metrics (10 days by default) and
samples all the queues at regular interval (10 seconds by default). If message counters
are enabled, these values should be configured to suit your messaging use case in
hornetq-configuration.xml
:
<!-- keep history for a week --> <message-counter-max-day-history>7</message-counter-max-day-history> <!-- sample the queues every minute (60000ms) --> <message-counter-sample-period>60000</message-counter-sample-period>
Message counters can be retrieved using the Management API. For example, to retrieve message counters on a JMS Queue using JMX:
// retrieve a connection to HornetQ's MBeanServer MBeanServerConnection mbsc = ... JMSQueueControlMBean queueControl = (JMSQueueControl)MBeanServerInvocationHandler.newProxyInstance(mbsc, on, JMSQueueControl.class, false); // message counters are retrieved as a JSON String String counters = queueControl.listMessageCounter(); // use the MessageCounterInfo helper class to manipulate message counters more easily MessageCounterInfo messageCounter = MessageCounterInfo.fromJSON(counters); System.out.format("%s message(s) in the queue (since last sample: %s)\n", messageCounter.getDepth(), messageCounter.getDepthDelta());
See Section 11.1.34, “Message Counter” for an example which shows how to use
message counters to retrieve information on a JMS Queue
.
Its possible to create and configure HornetQ resources via the admin console within the JBoss Application Server.
The Admin Console will allow you to create destinations (JMS Topics and Queues) and JMS Connection Factories.
Once logged in to the admin console you will see a JMS Manager item in the left hand tree. All HornetQ resources will be configured via this. This will have a child items for JMS Queues, Topics and Connection Factories, clicking on each node will reveal which resources are currently available. The following sections explain how to create and configure each resource in turn.
To create a new JMS Queue click on the JMS Queues item to reveal the available queues. On the right hand panel you will see an add a new resource button, click on this and then choose the default(JMS Queue) template and click continue. The important things to fill in here are the name of the queue and the JNDI name of the queue. The JNDI name is what you will use to look up the queue in JNDI from your client. For most queues this will be the only info you will need to provide as sensible defaults are provided for the others. You will also see a security roles section near the bottom. If you do not provide any roles for this queue then the servers default security configuration will be used, after you have created the queue these will be shown in the configuration. All configuration values, except the name and JNDI name, can be changed via the configuration tab after clicking on the queue in the admin console. The following section explains these in more detail
After highlighting the configuration you will see the following screen
The name and JNDI name cant be changed, if you want to change these recreate the queue with the appropriate settings. The rest of the configuration options, apart from security roles, relate to address settings for a particular address. The default address settings are picked up from the servers configuration, if you change any of these settings or create a queue via the console a new Address Settings enrty will be added. For a full explanation on Address Settings see Section 25.3, “Configuring Queues Via Address Settings”
To delete a queue simply click on the delete button beside the queue name in the main JMS Queues screen. This will also delete any address settings or security settings previously created for the queues address
The last part of the configuration options are security roles. If non are provided on creation then the servers default security settings will be shown. If these are changed or updated then new securty settings are created for the address of this queue. For more information on securuty setting see Chapter 31, Security
It is also possible via the metrics tab to view statistics for this queue. This will show statistics such as message count, consumer count etc.
Operations can be performed on a queue via the control tab. This will allow you to start and stop the queue, list,move,expire and delete messages from the queue and other useful operations. To invoke an operation click on the button for the operation you want, this will take you to a screen where you can parameters for the opertion can be set. Once set clicking the ok button will invoke the operation, results appear at the bottom of the screen.
Creating and configuring JMS Topics is almost identical to creating queues. The only difference is that the configuration will be applied to the queue representing a subscription.
This chapter describes how security works with HornetQ and how you can configure it. To
disable security completely simply set the security-enabled
property to
false in the hornetq-configuration.xml
file.
For performance reasons security is cached and invalidated every so long. To change this
period set the property security-invalidation-interval
, which is in
milliseconds. The default is 10000
ms.
HornetQ contains a flexible role-based security model for applying security to queues, based on their addresses.
As explained in Chapter 8, Using Core, HornetQ core consists mainly of sets of queues bound to addresses. A message is sent to an address and the server looks up the set of queues that are bound to that address, the server then routes the message to those set of queues.
HornetQ allows sets of permissions to be defined against the queues based on their
address. An exact match on the address can be used or a wildcard match can be used using
the wildcard characters '#
' and '*
'.
Seven different permissions can be given to the set of queues which match the address. Those permissions are:
createDurableQueue
. This permission allows the user to
create a durable queue under matching addresses.
deleteDurableQueue
. This permission allows the user to
delete a durable queue under matching addresses.
createNonDurableQueue
. This permission allows the user to create
a non-durable queue under matching addresses.
deleteNonDurableQueue
. This permission allows the user to delete
a non-durable queue under matching addresses.
send
. This permission allows the user to send a message to
matching addresses.
consume
. This permission allows the user to consume a
message from a queue bound to matching addresses.
manage
. This permission allows the user to invoke
management operations by sending management messages to the management
address.
For each permission, a list of roles who are granted that permission is specified. If the user has any of those roles, he/she will be granted that permission for that set of addresses.
Let's take a simple example, here's a security block from hornetq-configuration.xml
or hornetq-queues.xml
file:
<security-setting match="globalqueues.europe.#"> <permission type="createDurableQueue" roles="admin"/> <permission type="deleteDurableQueue" roles="admin"/> <permission type="createNonDurableQueue" roles="admin, guest, europe-users"/> <permission type="deleteNonDurableQueue" roles="admin, guest, europe-users"/> <permission type="send" roles="admin, europe-users"/> <permission type="consume" roles="admin, europe-users"/> </security-setting>
The '#
' character signifies "any sequence of words". Words are
delimited by the '.
' character. For a full description of the
wildcard syntax please see Chapter 13, Understanding the HornetQ Wildcard Syntax. The above security block
applies to any address that starts with the string "globalqueues.europe.":
Only users who have the admin
role can create or delete durable
queues bound to an address that starts with the string "globalqueues.europe."
Any users with the roles admin
, guest
, or
europe-users
can create or delete temporary queues bound to an
address that starts with the string "globalqueues.europe."
Any users with the roles admin
or europe-users
can send messages to these addresses or consume messages from queues bound to an address
that starts with the string "globalqueues.europe."
The mapping between a user and what roles they have is handled by the security manager. HornetQ ships with a user manager that reads user credentials from a file on disk, and can also plug into JAAS or JBoss Application Server security.
For more information on configuring the security manager, please see Section 31.4, “Changing the security manager”.
There can be zero or more security-setting
elements in each xml
file. Where more than one match applies to a set of addresses the more
specific match takes precedence.
Let's look at an example of that, here's another security-setting
block:
<security-setting match="globalqueues.europe.orders.#"> <permission type="send" roles="europe-users"/> <permission type="consume" roles="europe-users"/> </security-setting>
In this security-setting
block the match
'globalqueues.europe.orders.#' is more specific than the previous match
'globalqueues.europe.#'. So any addresses which match 'globalqueues.europe.orders.#'
will take their security settings only from the latter
security-setting block.
Note that settings are not inherited from the former block. All the settings will be
taken from the more specific matching block, so for the address
'globalqueues.europe.orders.plastics' the only permissions that exist are send
and consume
for the role europe-users. The
permissions createDurableQueue
, deleteDurableQueue
, createNonDurableQueue
, deleteNonDurableQueue
are not inherited from the other security-setting
block.
By not inheriting permissions, it allows you to effectively deny permissions in more specific security-setting blocks by simply not specifying them. Otherwise it would not be possible to deny permissions in sub-groups of addresses.
When messaging clients are connected to servers, or servers are connected to other servers (e.g. via bridges) over an untrusted network then HornetQ allows that traffic to be encrypted using the Secure Sockets Layer (SSL) transport.
For more information on configuring the SSL transport, please see Chapter 16, Configuring the Transport.
HornetQ ships with a security manager implementation that reads user credentials, i.e.
user names, passwords and role information from an xml file on the classpath called
hornetq-users.xml
. This is the default security manager.
If you wish to use this security manager, then users, passwords and roles can easily be added into this file.
Let's take a look at an example file:
<configuration xmlns="urn:hornetq" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="urn:hornetq ../schemas/hornetq-users.xsd "> <defaultuser name="guest" password="guest"> <role name="guest"/> </defaultuser> <user name="tim" password="marmite"> <role name="admin"/> </user> <user name="andy" password="doner_kebab"> <role name="admin"/> <role name="guest"/> </user> <user name="jeff" password="camembert"> <role name="europe-users"/> <role name="guest"/> </user> </configuration>
The first thing to note is the element defaultuser
. This defines
what user will be assumed when the client does not specify a username/password when
creating a session. In this case they will be the user guest
and have
the role also called guest
. Multiple roles can be specified for a
default user.
We then have three more users, the user tim
has the role admin
. The user andy
has the roles admin
and guest
, and the user jeff
has the roles europe-users
and guest
.
If you do not want to use the default security manager then you can specify a
different one by editing the file hornetq-beans.xml
(or hornetq-jboss-beans.xml
if you're running JBoss Application Server) and
changing the class for the HornetQSecurityManager
bean.
Let's take a look at a snippet from the default beans file:
<bean name="HornetQSecurityManager" class="org.hornetq.spi.core.security.HornetQSecurityManagerImpl"> <start ignored="true"/> <stop ignored="true"/> </bean>
The class org.hornetq.spi.core.security.HornetQSecurityManagerImpl
is the default security manager that is used by the standalone server.
HornetQ ships with two other security manager implementations you can use
off-the-shelf; one a JAAS security manager and another for integrating with JBoss
Application Sever security, alternatively you could write your own implementation by
implementing the org.hornetq.core.security.SecurityManager
interface,
and specifying the classname of your implementation in the file hornetq-beans.xml
(or hornetq-jboss-beans.xml
if
you're running JBoss Application Server).
These two implementations are discussed in the next two sections.
JAAS stands for 'Java Authentication and Authorization Service' and is a standard part of the Java platform. It provides a common API for security authentication and authorization, allowing you to plugin your pre-built implementations.
To configure the JAAS security manager to work with your pre-built JAAS infrastructure
you need to specify the security manager as a JAASSecurityManager
in
the beans file. Here's an example:
<bean name="HornetQSecurityManager" class="org.hornetq.integration.jboss.security.JAASSecurityManager"> <start ignored="true"/> <stop ignored="true"/> <property name="ConfigurationName">org.hornetq.jms.example.ExampleLoginModule</property> <property name="Configuration"> <inject bean="ExampleConfiguration"/> </property> <property name="CallbackHandler"> <inject bean="ExampleCallbackHandler"/> </property> </bean>
Note that you need to feed the JAAS security manager with three properties:
ConfigurationName: the name of the LoginModule
implementation that JAAS must use
Configuration: the Configuration
implementation used by
JAAS
CallbackHandler: the CallbackHandler
implementation to use
if user interaction are required
See Section 11.1.27, “JAAS” for an example which shows how HornetQ can be configured to use JAAS.
The JBoss AS security manager is used when running HornetQ inside the JBoss Application server. This allows tight integration with the JBoss Application Server's security model.
The class name of this security manager is org.hornetq.integration.jboss.security.JBossASSecurityManager
Take a look at one of the default hornetq-jboss-beans.xml
files for
JBoss Application Server that are bundled in the distribution for an example of how this
is configured.
JBoss can be configured to allow client login, basically this is when a JEE component such as a Servlet
or EJB sets security credentials on the current security context and these are used throughout the call.
If you would like these credentials to be used by HornetQ when sending or consuming messages then
set allowClientLogin
to true. This will bypass HornetQ authentication and propgate the
provided Security Context. If you would like HornetQ to authenticate using the propogated security then set the
authoriseOnClientLogin
to true also.
There is more info on using the JBoss client login module here
If messages are sent non blocking then there is a chance that these could arrive on the server after the calling thread has completed meaning that the security context has been cleared. If this is the case then messages will need to be sent blocking
In order for cluster connections to work correctly, each node in the cluster must make connections to the other nodes. The username/password they use for this should always be changed from the installation default to prevent a security risk.
Please see Chapter 30, Management for instructions on how to do this.
HornetQ can be easily installed in JBoss Application Server 4 or later. For details on installing HornetQ in the JBoss Application Server please refer to quick-start guide.
Since HornetQ also provides a JCA adapter, it is also possible to integrate HornetQ as a JMS provider in other JEE compliant app servers. For instructions on how to integrate a remote JCA adaptor into another application sever, please consult the other application server's instructions.
A JCA Adapter basically controls the inflow of messages to Message-Driven Beans (MDBs) and the outflow of messages sent from other JEE components, e.g. EJBs and Servlets.
This section explains the basics behind configuring the different JEE components in the AS.
The delivery of messages to an MDB using HornetQ is configured on the JCA Adapter via
a configuration file ra.xml
which can be found under the jms-ra.rar
directory. By default this is configured to consume
messages using an InVM connector from the instance of HornetQ running within the
application server. The configuration properties are listed later in this chapter.
All MDBs however need to have the destination type and the destination configured. The following example shows how this can be done using annotations:
@MessageDriven(name = "MDBExample", activationConfig = { @ActivationConfigProperty(propertyName = "destinationType", propertyValue = "javax.jms.Queue"), @ActivationConfigProperty(propertyName = "destination", propertyValue = "queue/testQueue") }) @ResourceAdapter("hornetq-ra.rar") public class MDBExample implements MessageListener { public void onMessage(Message message)... }
In this example you can see that the MDB will consume messages from a queue that is
mapped into JNDI with the binding queue/testQueue
. This queue must be
preconfigured in the usual way using the HornetQ configuration files.
The ResourceAdapter
annotation is used to specify which adaptor
should be used. To use this you will need to import org.jboss.ejb3.annotation.ResourceAdapter
for JBoss AS 5.X and later version which can be found in the
jboss-ejb3-ext-api.jar
which can be found in the JBoss
repository. For JBoss AS 4.X, the annotation to use is org.jboss.annotation.ejb.ResourceAdaptor
.
Alternatively you can add use a deployment descriptor and add something like
the following to jboss.xml
<message-driven> <ejb-name>ExampleMDB</ejb-name> <resource-adapter-name>hornetq-ra.rar</resource-adapter-name> </message-driven>
You
can also rename the hornetq-ra.rar directory to jms-ra.rar and neither the annotation or
the extra descriptor information will be needed. If you do this you will need to edit
the jms-ds.xml
datasource file and change rar-name
element.
HornetQ is the default JMS provider for JBoss AS 6. Starting with this AS version, HornetQ resource
adapter is named jms-ra.rar
and you no longer need to annotate the MDB for the resource adapter name.
All the examples shipped with the HornetQ distribution use the annotation.
When an MDB is using Container-Managed Transactions (CMT), the delivery of the message is done within the scope of a JTA transaction. The commit or rollback of this transaction is controlled by the container itself. If the transaction is rolled back then the message delivery semantics will kick in (by default, it will try to redeliver the message up to 10 times before sending to a DLQ). Using annotations this would be configured as follows:
@MessageDriven(name = "MDB_CMP_TxRequiredExample", activationConfig = { @ActivationConfigProperty(propertyName = "destinationType", propertyValue = "javax.jms.Queue"), @ActivationConfigProperty(propertyName = "destination", propertyValue = "queue/testQueue") }) @TransactionManagement(value= TransactionManagementType.CONTAINER) @TransactionAttribute(value= TransactionAttributeType.REQUIRED) @ResourceAdapter("hornetq-ra.rar") public class MDB_CMP_TxRequiredExample implements MessageListener { public void onMessage(Message message)... }
The TransactionManagement
annotation tells the container to manage the
transaction. The TransactionAttribute
annotation tells the container that a JTA
transaction is required for this MDB. Note that the only other valid value for this
is TransactionAttributeType.NOT_SUPPORTED
which tells the
container that this MDB does not support JTA transactions and one should not be
created.
It is also possible to inform the container that it must rollback the transaction
by calling setRollbackOnly
on the MessageDrivenContext
. The code for this would look something
like:
@Resource MessageDrivenContextContext ctx; public void onMessage(Message message) { try { //something here fails } catch (Exception e) { ctx.setRollbackOnly(); } }
If you do not want the overhead of an XA transaction being created every time but you would still like the message delivered within a transaction (i.e. you are only using a JMS resource) then you can configure the MDB to use a local transaction. This would be configured as such:
@MessageDriven(name = "MDB_CMP_TxLocalExample", activationConfig = { @ActivationConfigProperty(propertyName = "destinationType", propertyValue = "javax.jms.Queue"), @ActivationConfigProperty(propertyName = "destination", propertyValue = "queue/testQueue"), @ActivationConfigProperty(propertyName = "useLocalTx", propertyValue = "true") }) @TransactionManagement(value = TransactionManagementType.CONTAINER) @TransactionAttribute(value = TransactionAttributeType.NOT_SUPPORTED) @ResourceAdapter("hornetq-ra.rar") public class MDB_CMP_TxLocalExample implements MessageListener { public void onMessage(Message message)... }
Message-driven beans can also be configured to use Bean-Managed Transactions (BMT). In this case a User Transaction is created. This would be configured as follows:
@MessageDriven(name = "MDB_BMPExample", activationConfig = { @ActivationConfigProperty(propertyName = "destinationType", propertyValue = "javax.jms.Queue"), @ActivationConfigProperty(propertyName = "destination", propertyValue = "queue/testQueue"), @ActivationConfigProperty(propertyName = "acknowledgeMode", propertyValue = "Dups-ok-acknowledge") }) @TransactionManagement(value= TransactionManagementType.BEAN) @ResourceAdapter("hornetq-ra.rar") public class MDB_BMPExample implements MessageListener { public void onMessage(Message message) }
When using Bean-Managed Transactions the message delivery to the MDB will occur
outside the scope of the user transaction and use the acknowledge mode specified by
the user with the acknowledgeMode
property. There are only 2
acceptable values for this Auto-acknowledge
and Dups-ok-acknowledge
. Please note that because the message delivery is outside
the scope of the transaction a failure within the MDB will not cause the message to
be redelivered.
A user would control the lifecycle of the transaction something like the following:
@Resource MessageDrivenContext ctx; public void onMessage(Message message) { UserTransaction tx; try { TextMessage textMessage = (TextMessage)message; String text = textMessage.getText(); UserTransaction tx = ctx.getUserTransaction(); tx.begin(); //do some stuff within the transaction tx.commit(); } catch (Exception e) { tx.rollback(); } }
It is also possible to use MDBs with message selectors. To do this simple define your message selector as follows:
@MessageDriven(name = "MDBMessageSelectorExample", activationConfig = { @ActivationConfigProperty(propertyName = "destinationType", propertyValue = "javax.jms.Queue"), @ActivationConfigProperty(propertyName = "destination", propertyValue = "queue/testQueue"), @ActivationConfigProperty(propertyName = "messageSelector", propertyValue = "color = 'RED'") }) @TransactionManagement(value= TransactionManagementType.CONTAINER) @TransactionAttribute(value= TransactionAttributeType.REQUIRED) @ResourceAdapter("hornetq-ra.rar") public class MDBMessageSelectorExample implements MessageListener { public void onMessage(Message message).... }
The JCA adapter can also be used for sending messages. The Connection Factory to use
is configured by default in the jms-ds.xml
file and is mapped to
java:/JmsXA
. Using this from within a JEE component will mean
that the sending of the message will be done as part of the JTA transaction being used
by the component.
This means that if the sending of the message fails the overall transaction would rollback and the message be re-sent. Heres an example of this from within an MDB:
@MessageDriven(name = "MDBMessageSendTxExample", activationConfig = { @ActivationConfigProperty(propertyName = "destinationType", propertyValue = "javax.jms.Queue"), @ActivationConfigProperty(propertyName = "destination", propertyValue = "queue/testQueue") }) @TransactionManagement(value= TransactionManagementType.CONTAINER) @TransactionAttribute(value= TransactionAttributeType.REQUIRED) @ResourceAdapter("hornetq-ra.rar") public class MDBMessageSendTxExample implements MessageListener { @Resource(mappedName = "java:/JmsXA") ConnectionFactory connectionFactory; @Resource(mappedName = "queue/replyQueue") Queue replyQueue; public void onMessage(Message message) { Connection conn = null; try { //Step 9. We know the client is sending a text message so we cast TextMessage textMessage = (TextMessage)message; //Step 10. get the text from the message. String text = textMessage.getText(); System.out.println("message " + text); conn = connectionFactory.createConnection(); Session sess = conn.createSession(false, Session.AUTO_ACKNOWLEDGE); MessageProducer producer = sess.createProducer(replyQueue); producer.send(sess.createTextMessage("this is a reply")); } catch (Exception e) { e.printStackTrace(); } finally { if(conn != null) { try { conn.close(); } catch (JMSException e) { } } } } }
In JBoss Application Server you can use the JMS JCA adapter for sending messages from EJBs (including Session, Entity and Message-Driven Beans), Servlets (including jsps) and custom MBeans.
Most application servers, including JBoss, allow you to configure how many MDB's there are in a pool. In
Jboss this is configured via the MaxPoolSize
parameter in the ejb3-interceptors-aop.xml file. Configuring
this has no actual effect on how many sessions/consumers there actually are created. This is because the Resource
Adaptor implementation knows nothing about the application servers MDB implementation. So even if you set the MDB
pool size to 1, 15 sessions/consumers will be created (this is the default). If you want to limit how many
sessions/consumers are created then you need to set the maxSession
parameter either on the
resource adapter itself or via an an Activation Config Property on the MDB itself
@MessageDriven(name = "MDBMessageSendTxExample", activationConfig = { @ActivationConfigProperty(propertyName = "destinationType", propertyValue = "javax.jms.Queue"), @ActivationConfigProperty(propertyName = "destination", propertyValue = "queue/testQueue"), @ActivationConfigProperty(propertyName = "maxSession", propertyValue = "1") }) @TransactionManagement(value= TransactionManagementType.CONTAINER) @TransactionAttribute(value= TransactionAttributeType.REQUIRED) @ResourceAdapter("hornetq-ra.rar") public class MyMDB implements MessageListener { ....}
The Java Connector Architecture (JCA) Adapter is what allows HornetQ to be integrated with JEE components such as MDBs and EJBs. It configures how components such as MDBs consume messages from the HornetQ server and also how components such as EJBs or Servlets can send messages.
The HornetQ JCA adapter is deployed via the jms-ra.rar
archive. The
configuration of the adapter is found in this archive under META-INF/ra.xml
.
The configuration will look something like the following:
<resourceadapter> <resourceadapter-class>org.hornetq.ra.HornetQResourceAdapter</resourceadapter-class> <config-property> <description>The transport type. Multiple connectors can be configured by using a comma separated list, i.e. org.hornetq.core.remoting.impl.invm.InVMConnectorFactory,org.hornetq.core.remoting.impl.invm.InVMConnectorFactory.</description> <config-property-name>ConnectorClassName</config-property-name> <config-property-type>java.lang.String</config-property-type> <config-property-value>org.hornetq.core.remoting.impl.invm.InVMConnectorFactory</config-property-value> </config-property> <config-property> <description>The transport configuration. These values must be in the form of key=val;key=val;, if multiple connectors are used then each set must be separated by a comma i.e. host=host1;port=5445,host=host2;port=5446. Each set of params maps to the connector classname specified.</description> <config-property-name>ConnectionParameters</config-property-name> <config-property-type>java.lang.String</config-property-type> <config-property-value>server-id=0</config-property-value> </config-property> <outbound-resourceadapter> <connection-definition> <managedconnectionfactory-class>org.hornetq.ra.HornetQRAManagedConnection Factory</managedconnectionfactory-class> <config-property> <description>The default session type</description> <config-property-name>SessionDefaultType</config-property-name> <config-property-type>java.lang.String</config-property-type> <config-property-value>javax.jms.Queue</config-property-value> </config-property> <config-property> <description>Try to obtain a lock within specified number of seconds; less than or equal to 0 disable this functionality</description> <config-property-name>UseTryLock</config-property-name> <config-property-type>java.lang.Integer</config-property-type> <config-property-value>0</config-property-value> </config-property> <connectionfactory-interface>org.hornetq.ra.HornetQRAConnectionFactory </connectionfactory-interface> <connectionfactororg.hornetq.ra.HornetQConnectionFactoryImplonFactoryImpl </connectionfactory-impl-class> <connection-interface>javax.jms.Session</connection-interface> <connection-impl-class>org.hornetq.ra.HornetQRASession </connection-impl-class> </connection-definition> <transaction-support>XATransaction</transaction-support> <authentication-mechanism> <authentication-mechanism-type>BasicPassword </authentication-mechanism-type> <credential-interface>javax.resource.spi.security.PasswordCredential </credential-interface> </authentication-mechanism> <reauthentication-support>false</reauthentication-support> </outbound-resourceadapter> <inbound-resourceadapter> <messageadapter> <messagelistener> <messagelistener-type>javax.jms.MessageListener</messagelistener-type> <activationspec> <activationspec-class>org.hornetq.ra.inflow.HornetQActivationSpec </activationspec-class> <required-config-property> <config-property-name>destination</config-property-name> </required-config-property> </activationspec> </messagelistener> </messageadapter> </inbound-resourceadapter> </resourceadapter>
There are three main parts to this configuration.
A set of global properties for the adapter
The configuration for the outbound part of the adapter. This is used for creating JMS resources within EE components.
The configuration of the inbound part of the adapter. This is used for controlling the consumption of messages via MDBs.
The first element you see is resourceadapter-class
which should
be left unchanged. This is the HornetQ resource adapter class.
After that there is a list of configuration properties. This will be where most of the configuration is done. The first two properties configure the transport used by the adapter and the rest configure the connection factory itself.
All connection factory properties will use the defaults if they are not provided, except
for the reconnectAttempts
which will default to -1. This
signifies that the connection should attempt to reconnect on connection
failure indefinitely. This is only used when the adapter is configured to
connect to a remote server as an InVM connector can never fail.
The following table explains what each property is for.
Table 32.1. Global Configuration Properties
Property Name | Property Type | Property Description |
---|---|---|
ConnectorClassName | String | The Connector class name (see Chapter 16, Configuring the Transport for more information). If multiple connectors are needed this should be provided as a comma separated list. |
ConnectionParameters | String | The transport configuration. These parameters must be in the form of
key1=val1;key2=val2; and will be specific to the connector used. If
multiple connectors are configured then params should be supplied for each connector
separated by a comma.
|
hA | boolean | True if high availability is needed. |
useLocalTx | boolean | True will enable local transaction optimisation. |
UserName | String | The user name to use when making a connection |
Password | String | The password to use when making a connection |
DiscoveryAddress | String | The discovery group address to use to autodetect a server |
DiscoveryPort | Integer | The port to use for discovery |
DiscoveryRefreshTimeout | Long | The timeout, in milliseconds, to refresh. |
DiscoveryInitialWaitTimeout | Long | The initial time to wait for discovery. |
ConnectionLoadBalancingPolicyClassName | String | The load balancing policy class to use. |
ConnectionTTL | Long | The time to live (in milliseconds) for the connection. |
CallTimeout | Long | the call timeout (in milliseconds) for each packet sent. |
DupsOKBatchSize | Integer | the batch size (in bytes) between acknowledgements when using DUPS_OK_ACKNOWLEDGE mode |
TransactionBatchSize | Integer | the batch size (in bytes) between acknowledgements when using a transactional session |
ConsumerWindowSize | Integer | the window size (in bytes) for consumer flow control |
ConsumerMaxRate | Integer | the fastest rate a consumer may consume messages per second |
ConfirmationWindowSize | Integer | the window size (in bytes) for reattachment confirmations |
ProducerMaxRate | Integer | the maximum rate of messages per second that can be sent |
MinLargeMessageSize | Integer | the size (in bytes) before a message is treated as large |
BlockOnAcknowledge | Boolean | whether or not messages are acknowledged synchronously |
BlockOnNonDurableSend | Boolean | whether or not non-durable messages are sent synchronously |
BlockOnDurableSend | Boolean | whether or not durable messages are sent synchronously |
AutoGroup | Boolean | whether or not message grouping is automatically used |
PreAcknowledge | Boolean | whether messages are pre acknowledged by the server before sending |
ReconnectAttempts | Integer | maximum number of retry attempts, default for the resource adpater is -1 (infinite attempts) |
RetryInterval | Long | the time (in milliseconds) to retry a connection after failing |
RetryIntervalMultiplier | Double | multiplier to apply to successive retry intervals |
FailoverOnServerShutdown | Boolean | If true client will reconnect to another server if available |
ClientID | String | the pre-configured client ID for the connection factory |
ClientFailureCheckPeriod | Long | the period (in ms) after which the client will consider the connection failed after not receiving packets from the server |
UseGlobalPools | Boolean | whether or not to use a global thread pool for threads |
ScheduledThreadPoolMaxSize | Integer | the size of the scheduled thread pool |
ThreadPoolMaxSize | Integer | the size of the thread pool |
SetupAttempts | Integer | Number of attempts to setup a JMS connection (default is 10, -1 means to attempt infinitely). It is possible that the MDB is deployed before the JMS resources are available. In that case, the resource adapter will try to setup several times until the resources are available. This applies only for inbound connections |
SetupInterval | Long | Interval in milliseconds between consecutive attemps to setup a JMS connection (default is 2000m). This applies only for inbound connections |
The outbound configuration should remain unchanged as they define connection
factories that are used by Java EE components. These Connection Factories can be
defined inside a configuration file that matches the name *-ds.xml
. You'll find a default jms-ds.xml
configuration under the hornetq
directory in the JBoss AS
deployment. The connection factories defined in this file inherit their
properties from the main ra.xml
configuration but can also be
overridden. The following example shows how to override them.
Please note that this configuration only applies when HornetQ resource adapter is installed in JBoss Application Server. If you are using another JEE application server please refer to your application servers documentation for how to do this.
<tx-connection-factory> <jndi-name>RemoteJmsXA</jndi-name> <xa-transaction/> <rar-name>jms-ra.rar</rar-name> <connection-definition>org.hornetq.ra.HornetQRAConnectionFactory </connection-definition> <config-property name="SessionDefaultType" type="String">javax.jms.Topic</config-property> <config-property name="ConnectorClassName" type="String"> org.hornetq.core.remoting.impl.netty.NettyConnectorFactory </config-property> <config-property name="ConnectionParameters" type="String"> port=5445</config-property> <max-pool-size>20</max-pool-size> </tx-connection-factory>
If the connector class name is overridden the all params must also be supplied.
In this example the connection factory will be bound to JNDI with the name
RemoteJmsXA
and can be looked up in the usual way using JNDI
or defined within the EJB or MDB as such:
@Resource(mappedName="java:/RemoteJmsXA") private ConnectionFactory connectionFactory;
The config-property
elements are what overrides those in the
ra.xml
configuration file. Any of the elements pertaining to the
connection factory can be overridden here.
The outbound configuration also defines additional properties in addition to the global configuration properties.
Table 32.2. Outbound Configuration Properties
Property Name | Property Type | Property Description |
---|---|---|
SessionDefaultType | String | the default session type |
UseTryLock | Integer | try to obtain a lock within specified number of seconds. less than or equal to 0 disable this functionality |
The inbound configuration should again remain unchanged. This controls what forwards messages onto MDBs. It is possible to override properties on the MDB by adding an activation configuration to the MDB itself. This could be used to configure the MDB to consume from a different server.
The inbound configuration also defines additional properties in addition to the global configuration properties.
Table 32.3. Inbound Configuration Properties
Property Name | Property Type | Property Description |
---|---|---|
Destination | String | JNDI name of the destination |
DestinationType | String | type of the destination, either javax.jms.Queue or javax.jms.Topic
(default is javax.jms.Queue) |
AcknowledgeMode | String | The Acknowledgment mode, either Auto-acknowledge or Dups-ok-acknowledge
(default is Auto-acknowledge). AUTO_ACKNOWLEDGE and DUPS_OK_ACKNOWLEDGE are acceptable values. |
MaxSession | Integer | Maximum number of session created by this inbound configuration (default is 15) |
MessageSelector | String | the message selector of the consumer |
SubscriptionDurability | String | Type of the subscription, either Durable or NonDurable |
SubscriptionName | String | Name of the subscription |
TransactionTimeout | Long | The transaction timeout in milliseconds (default is 0, the transaction does not timeout) |
UseJNDI | Boolean | Whether or not use JNDI to look up the destination (default is true) |
Sometime you may want your messaging server on a different machine or separate from the application server. If this is the case you will only need the hornetq client libs installed. This section explains what config to create and what jar dependencies are needed.
There are two configuration files needed to do this, one for the incoming adapter used for MDB's and one for outgoing connections managed by the JCA managed connection pool used by outgoing JEE components wanting outgoing connections.
Firstly you will need to create directory under the
deploy
directory ending in
.rar.
For this example we will name the directory hornetq-ra.rar
. This detail is
important as
the name of directory is referred to by the MDB's and the outgoing configuration.
The jboss default for this is jms-ra.rar
, If you don't want to have to
configure your
MDB's you can use this but you may need to remove the generic adaptor that uses this.
Under the
hornetq-ra.rar
directory you will need to create a
META-INF
directory into which you should create an
ra.xml
configuration file. You can find a template
for the
ra.xml
under the config directory of the HornetQ distribution.
To configure MDB's to consume messages from a remote HornetQ server you need to edit the
ra.xml
file under
deploy/hornet-ra.rar/META-INF
and change the transport type to
use a netty connector (instead of the invm connector that is defined) and configure its transport
params.
Heres an example of what this would look like:
<resourceadapter-class>org.hornetq.ra.HornetQResourceAdapter</resourceadapter-class> <config-property> <description>The transport type</description> <config-property-name>ConnectorClassName</config-property-name> <config-property-type>java.lang.String</config-property-type> <config-property-value>org.hornetq.core.remoting.impl.netty.NettyConnectorFactory</config-property-value> </config-property> <config-property> <description>The transport configuration. These values must be in the form of key=val;key=val;</description> <config-property-name>ConnectionParameters</config-property-name> <config-property-type>java.lang.String</config-property-type> <config-property-value>host=127.0.0.1;port=5446</config-property-value> </config-property>
If you want to provide a list of servers that the adapter can connect to you can provide a list of connectors, each separated by a comma.
<resourceadapter-class>org.hornetq.ra.HornetQResourceAdapter</resourceadapter-class> <config-property> <description>The transport type</description> <config-property-name>ConnectorClassName</config-property-name> <config-property-type>java.lang.String</config-property-type> <config-property-value>org.hornetq.core.remoting.impl.netty.NettyConnectorFactory,org.hornetq.core.remoting.impl.netty.NettyConnectorFactory</config-property-value> </config-property> <config-property> <description>The transport configuration. These values must be in the form of key=val;key=val;</description> <config-property-name>ConnectionParameters</config-property-name> <config-property-type>java.lang.String</config-property-type> <config-property-value>host=127.0.0.1;port=5446,host=127.0.0.2;port=5447</config-property-value> </config-property>
Make sure you provide parameters for each connector configured. The position of the params in the list maps to each connector provided.
This configures the resource adapter to connect to a server running on localhost listening on port 5446
You will also need to configure the outbound connection by creating a hornetq-ds.xml
and placing it under any directory that will be deployed under the deploy
directory.
In a standard HornetQ jboss configuration this would be under horneq
or hornetq.sar
but you can place it where ever you like. Actually as long as it ends in -ds.xml
you can
call it anything you like. You can again find a template for this file under the config directory of the
HornetQ distribution but called jms-ds.xml
which is the jboss default.
The following example shows a sample configuration
<tx-connection-factory> <jndi-name>RemoteJmsXA</jndi-name> <xa-transaction/> <rar-name>hornetq-ra.rar</rar-name> <connection-definition>org.hornetq.ra.HornetQRAConnectionFactory</connection-definition> <config-property name="SessionDefaultType" type="java.lang.String">javax.jms.Topic</config-property> <config-property name="ConnectorClassName" type="java.lang.String">org.hornetq.core.remoting.impl.netty.NettyConnectorFactory</config-property> <config-property name="ConnectionParameters" type="java.lang.String">host=127.0.0.1;port=5446</config-property> <max-pool-size>20</max-pool-size> </tx-connection-factory>
Again you will see that this uses the netty connector type and will connect to the HornetQ server
running on localhost and listening on port 5446. JEE components can access this by using JNDI and looking
up the connection factory using JNDI using java:/RemoteJmsXA
, you can see that this
is defined under thejndi-name
attribute. You will also note that the outgoing connection
will be created by the resource adaptor configured under the directory hornetq-ra.rar
as explained in the last section.
Also if you want to configure multiple connectors do this as a comma separated list as in the ra configuration.
This is a list of the HornetQ and third party jars needed
Table 32.4. Jar Dependencies
Jar Name | Description | Location |
---|---|---|
hornetq-ra.jar | The HornetQ resource adaptor classes | deploy/hornetq-ra.rar or equivelant |
hornetq-core-client.jar | The HornetQ core client classes | either in the config lib, i.e. default/lib or the common lib dir, i.e. $JBOSS_HOME/common lib |
hornetq-jms-client.jar | The HornetQ JMS classes | as above |
netty.jar | The Netty transport classes | as above |
This is a step by step guide on how to configure a JBoss application server that doesn't have HornetQ installed to use a remote instance of HornetQ
Firstly download and install JBoss AS 5 as per the JBoss installation guide and HornetQ as per the HornetQ installation guide. After thatt he following steps are required
Copy the following jars from the HornetQ distribution to the lib
directory of
which ever JBossAs configuration you have chosen, i.e. default
.
hornetq-core-client.jar
hornetq-jms-client.jar
hornetq-ra.jar (this can be found inside the hornetq-ra.rar
archive)
netty.jar
create the directories hornetq-ra.rar
and hornetq-ra.rar/META-INF
under the deploy
directory in your JBoss config directory
under the hornetq-ra.rar/META-INF
create a ra.xml
file or
copy it from the HornetQ distribution (again it can be found in the hornetq-ra.rar
archive)
and configure it as follows
<?xml version="1.0" encoding="UTF-8"?>
<connector xmlns="http://java.sun.com/xml/ns/j2ee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee
http://java.sun.com/xml/ns/j2ee/connector_1_5.xsd"
version="1.5">
<description>HornetQ 2.0 Resource Adapter Alternate Configuration</description>
<display-name>HornetQ 2.0 Resource Adapter Alternate Configuration</display-name>
<vendor-name>Red Hat Middleware LLC</vendor-name>
<eis-type>JMS 1.1 Server</eis-type>
<resourceadapter-version>1.0</resourceadapter-version>
<license>
<description>
Copyright 2009 Red Hat, Inc.
Red Hat licenses this file to you under the Apache License, version
2.0 (the "License"); you may not use this file except in compliance
with the License. You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
implied. See the License for the specific language governing
permissions and limitations under the License.
</description>
<license-required>true</license-required>
</license>
<resourceadapter>
<resourceadapter-class>org.hornetq.ra.HornetQResourceAdapter</resourceadapter-class>
<config-property>
<description>The transport type</description>
<config-property-name>ConnectorClassName</config-property-name>
<config-property-type>java.lang.String</config-property-type>
<config-property-value>org.hornetq.core.remoting.impl.netty.NettyConnectorFactory</config-property-value>
</config-property>
<config-property>
<description>The transport configuration. These values must be in the form of key=val;key=val;</description>
<config-property-name>ConnectionParameters</config-property-name>
<config-property-type>java.lang.String</config-property-type>
<config-property-value>host=127.0.0.1;port=5445</config-property-value>
</config-property>
<outbound-resourceadapter>
<connection-definition>
<managedconnectionfactory-class>org.hornetq.ra.HornetQRAManagedConnectionFactory</managedconnectionfactory-class>
<config-property>
<description>The default session type</description>
<config-property-name>SessionDefaultType</config-property-name>
<config-property-type>java.lang.String</config-property-type>
<config-property-value>javax.jms.Queue</config-property-value>
</config-property>
<config-property>
<description>Try to obtain a lock within specified number of seconds; less than or equal to 0 disable this functionality</description>
<config-property-name>UseTryLock</config-property-name>
<config-property-type>java.lang.Integer</config-property-type>
<config-property-value>0</config-property-value>
</config-property>
<connectionfactory-interface>org.hornetq.ra.HornetQRAConnectionFactory</connectionfactory-interface>
<connectionfactory-impl-class>org.hornetq.ra.HornetQRAConnectionFactoryImpl</connectionfactory-impl-class>
<connection-interface>javax.jms.Session</connection-interface>
<connection-impl-class>org.hornetq.ra.HornetQRASession</connection-impl-class>
</connection-definition>
<transaction-support>XATransaction</transaction-support>
<authentication-mechanism>
<authentication-mechanism-type>BasicPassword</authentication-mechanism-type>
<credential-interface>javax.resource.spi.security.PasswordCredential</credential-interface>
</authentication-mechanism>
<reauthentication-support>false</reauthentication-support>
</outbound-resourceadapter>
<inbound-resourceadapter>
<messageadapter>
<messagelistener>
<messagelistener-type>javax.jms.MessageListener</messagelistener-type>
<activationspec>
<activationspec-class>org.hornetq.ra.inflow.HornetQActivationSpec</activationspec-class>
<required-config-property>
<config-property-name>destination</config-property-name>
</required-config-property>
</activationspec>
</messagelistener>
</messageadapter>
</inbound-resourceadapter>
</resourceadapter>
</connector>
The important part of this configuration is the part in bold, i.e. <config-property-value>host=127.0.0.1;port=5445</config-property-value>. This should be configured to the host and port of the remote HornetQ server.
At this point you should be able to now deploy MDB's that consume from the remote server. You will however,
have to make sure that your MDB's have the annotation @ResourceAdapter("hornetq-ra.rar")
added, this is illustrated in the Section 32.1, “Configuring Message-Driven Beans” section.
If you don't want to add this annotation then you can delete the generic resource adapter jms-ra.rar
and rename the hornetq-ra.rar
to this.
If you also want to use the remote HornetQ server for outgoing connections, i.e. sending messages, then do the following:
Create a file called hornetq-ds.xml
in the deploy
directory
(in fact you can call this anything you want as long as it ends in -ds.xml
). Then
add the following:
<connection-factories> <!-- JMS XA Resource adapter, use this for outbound JMS connections. Inbound connections are defined at the @MDB activation or at the resource-adapter properties. --> <tx-connection-factory> <jndi-name>RemoteJmsXA</jndi-name> <xa-transaction/> <rar-name>hornetq-ra.rar</rar-name> <connection-definition>org.hornetq.ra.HornetQRAConnectionFactory</connection-definition> <config-property name="SessionDefaultType" type="java.lang.String">javax.jms.Topic</config-property> <config-property name="ConnectorClassName" type="java.lang.String">org.hornetq.core.remoting.impl.netty.NettyConnectorFactory</config-property> <config-property name="ConnectionParameters" type="java.lang.String">host=127.0.0.1;port=5445</config-property> <max-pool-size>20</max-pool-size> </tx-connection-factory> </connection-factories>
Again you will see that the host and port are configured here to match the remote HornetQ servers configuration. The other important attributes are:
jndi-name - This is the name used to look up the JMS connection factory from within your JEE client
rar-name - This should match the directory that you created to hold the Resource Adapter configuration
Now you should be able to send messages using the JCA JMS connection pooling within an XA transaction.
The steps to do this are exactly the same as for JBoss 4, you will have to create a jboss.xml definition file for your MDB with the following entry
<message-driven> <ejb-name>MyMDB</ejb-name> <resource-adapter-name>jms-ra.rar</resource-adapter-name> </message-driven>
Also you will need to edit the standardjboss.xml
and uncomment the section with the
following 'Uncomment to use JMS message inflow from jmsra.rar' and then comment out the invoker-proxy-binding
called 'message-driven-bean'
If you are using JNDI to look-up JMS queues, topics and connection factories from a cluster of servers, it is likely you will want to use HA-JNDI so that your JNDI look-ups will continue to work if one or more of the servers in the cluster fail.
HA-JNDI is a JBoss Application Server service which allows you to use JNDI from clients without them having to know the exact JNDI connection details of every server in the cluster. This service is only available if using a cluster of JBoss Application Server instances.
To use it use the following properties when connecting to JNDI.
Hashtable<String, String> jndiParameters = new Hashtable<String, String>(); jndiParameters.put("java.naming.factory.initial", "org.jnp.interfaces.NamingContextFactory"); jndiParameters.put("java.naming.factory.url.pkgs=", "org.jboss.naming:org.jnp.interfaces"); initialContext = new InitialContext(jndiParameters);
For more information on using HA-JNDI see the JBoss Application Server clustering documentation
XA recovery deals with system or application failures to ensure that of a transaction are applied consistently to all resources affected by the transaction, even if any of the application processes or the machine hosting them crash or lose network connectivity. For more information on XA Recovery,please refer to JBoss Transactions.
When HornetQ is integrated with JBoss AS, it can take advantage of JBoss Transactions to provide recovery of messaging resources. If messages are involved in a XA transaction, in the event of a server crash, the recovery manager will ensure that the transactions are recovered and the messages will either be committed or rolled back (depending on the transaction outcome) when the server is restarted.
To enable HornetQ's XA Recovery, the Recovery Manager must be configured to connect
to HornetQ to recover its resources. The following property must be added to the
jta
section of conf/jbossts-properties.xml
of JBoss AS profiles:
<properties depends="arjuna" name="jta"> ... <property name="com.arjuna.ats.jta.recovery.XAResourceRecovery.HornetQ1" value="org.hornetq.jms.server.recovery.HornetQXAResourceRecovery;[connection configuration]"/> <property name="com.arjuna.ats.jta.xaRecoveryNode" value="1"/> </properties>
The [connection configuration]
contains all the information
required to connect to HornetQ node under the form [connector factory class
name],[user name], [password], [connector parameters]
.
[connector factory class name]
corresponds to the name
of the ConnectorFactory
used to connect to HornetQ.
Values can be org.hornetq.core.remoting.impl.invm.InVMConnectorFactory
or
org.hornetq.core.remoting.impl.netty.NettyConnectorFactory
[user name]
is the user name to create a client
session. It is optional
[password]
is the password to create a client session.
It is mandatory only if the user name is specified
[connector parameters]
is a list of comma-separated
key=value pair which are passed to the connector factory (see Chapter 16, Configuring the Transport for a list of the transport
parameters).
Also note the com.arjuna.ats.jta.xaRecoveryNode
parameter. If you want recovery
enabled then this must be configured to what ever the tx node id is set to, this is configured in the
same file by the com.arjuna.ats.arjuna.xa.nodeIdentifier
property.
HornetQ must have a valid acceptor which corresponds to the connector
specified in conf/jbossts-properties.xml
.
If HornetQ is configured with a default in-vm acceptor:
<acceptor name="in-vm"> <factory-class>org.hornetq.core.remoting.impl.invm.InVMAcceptorFactory</factory-class> </acceptor>
the corresponding configuration in conf/jbossts-properties.xml
is:
<property name="com.arjuna.ats.jta.recovery.XAResourceRecovery.HORNETQ1" value="org.hornetq.jms.server.recovery.HornetQXAResourceRecovery;org.hornetq.core.remoting.impl.invm.InVMConnectorFactory"/>
If it is now configured with a netty acceptor on a non-default port:
<acceptor name="netty"> <factory-class>org.hornetq.core.remoting.impl.netty.NettyAcceptorFactory</factory-class> <param key="port" value="8888"/> </acceptor>
the corresponding configuration in conf/jbossts-properties.xml
is:
<property name="com.arjuna.ats.jta.recovery.XAResourceRecovery.HORNETQ1" value="org.hornetq.jms.server.recovery.HornetQXAResourceRecovery;org.hornetq.core.remoting.impl.netty.NettyConnectorFactory, , , port=8888"/>
Note the additional commas to skip the user and password before connector parameters
If the recovery must use admin, adminpass
, the
configuration would have been:
<property name="com.arjuna.ats.jta.recovery.XAResourceRecovery.HORNETQ1" value="org.hornetq.jms.server.recovery.HornetQXAResourceRecovery;org.hornetq.core.remoting.impl.netty.NettyConnectorFactory, admin, adminpass, port=8888"/>
Configuring HornetQ with an invm acceptor and configuring the Recovery Manager with an invm connector is the recommended way to enable XA Recovery.
See Section 11.3.9, “XA Recovery” which shows how to configure XA Recovery and recover messages after a server crash.
HornetQ includes a fully functional JMS message bridge.
The function of the bridge is to consume messages from a source queue or topic, and send them to a target queue or topic, typically on a different server.
The source and target servers do not have to be in the same cluster which makes bridging suitable for reliably sending messages from one cluster to another, for instance across a WAN, and where the connection may be unreliable.
A bridge can be deployed as a standalone application, with HornetQ standalone server or inside a JBoss AS instance. The source and the target can be located in the same virtual machine or another one.
The bridge can also be used to bridge messages from other non HornetQ JMS servers, as long as they are JMS 1.1 compliant.
Do not confuse a JMS bridge with a core bridge. A JMS bridge can be used to bridge any two JMS 1.1 compliant JMS providers and uses the JMS API. A core bridge (described in Chapter 36, Core Bridges) is used to bridge any two HornetQ instances and uses the core API. Always use a core bridge if you can in preference to a JMS bridge. The core bridge will typically provide better performance than a JMS bridge. Also the core bridge can provide once and only once delivery guarantees without using XA.
The bridge has built-in resilience to failure so if the source or target server connection is lost, e.g. due to network failure, the bridge will retry connecting to the source and/or target until they come back online. When it comes back online it will resume operation as normal.
The bridge can be configured with an optional JMS selector, so it will only consume messages matching that JMS selector
It can be configured to consume from a queue or a topic. When it consumes from a topic it can be configured to consume using a non durable or durable subscription
Typically, the bridge is deployed by the JBoss Micro Container via a beans configuration file. This would typically be deployed inside the JBoss Application Server and the following example shows an example of a beans file that bridges 2 destinations which are actually on the same server.
<?xml version="1.0" encoding="UTF-8"?> <deployment xmlns="urn:jboss:bean-deployer:2.0"> <bean name="JMSBridge" class="org.hornetq.api.jms.bridge.impl.JMSBridgeImpl"> <!-- HornetQ must be started before the bridge --> <depends>HornetQServer</depends> <constructor> <!-- Source ConnectionFactory Factory --> <parameter> <inject bean="SourceCFF"/> </parameter> <!-- Target ConnectionFactory Factory --> <parameter> <inject bean="TargetCFF"/> </parameter> <!-- Source DestinationFactory --> <parameter> <inject bean="SourceDestinationFactory"/> </parameter> <!-- Target DestinationFactory --> <parameter> <inject bean="TargetDestinationFactory"/> </parameter> <!-- Source User Name (no username here) --> <parameter><null /></parameter> <!-- Source Password (no password here)--> <parameter><null /></parameter> <!-- Target User Name (no username here)--> <parameter><null /></parameter> <!-- Target Password (no password here)--> <parameter><null /></parameter> <!-- Selector --> <parameter><null /></parameter> <!-- Failure Retry Interval (in ms) --> <parameter>5000</parameter> <!-- Max Retries --> <parameter>10</parameter> <!-- Quality Of Service --> <parameter>ONCE_AND_ONLY_ONCE</parameter> <!-- Max Batch Size --> <parameter>1</parameter> <!-- Max Batch Time (-1 means infinite) --> <parameter>-1</parameter> <!-- Subscription name (no subscription name here)--> <parameter><null /></parameter> <!-- Client ID (no client ID here)--> <parameter><null /></parameter> <!-- Add MessageID In Header --> <parameter>true</parameter> <!-- register the JMS Bridge in the AS MBeanServer --> <parameter> <inject bean="MBeanServer"/> </parameter> <parameter>org.hornetq:service=JMSBridge</parameter> </constructor> <property name="transactionManager"> <inject bean="RealTransactionManager"/> </property> </bean> <!-- SourceCFF describes the ConnectionFactory used to connect to the source destination --> <bean name="SourceCFF" class="org.hornetq.api.jms.bridge.impl.JNDIConnectionFactoryFactory"> <constructor> <parameter> <inject bean="JNDI" /> </parameter> <parameter>/ConnectionFactory</parameter> </constructor> </bean> <!-- TargetCFF describes the ConnectionFactory used to connect to the target destination --> <bean name="TargetCFF" class="org.hornetq.api.jms.bridge.impl.JNDIConnectionFactoryFactory"> <constructor> <parameter> <inject bean="JNDI" /> </parameter> <parameter>/ConnectionFactory</parameter> </constructor> </bean> <!-- SourceDestinationFactory describes the Destination used as the source --> <bean name="SourceDestinationFactory" class="org.hornetq.api.jms.bridge.impl.JNDIDestinationFactory"> <constructor> <parameter> <inject bean="JNDI" /> </parameter> <parameter>/queue/source</parameter> </constructor> </bean> <!-- TargetDestinationFactory describes the Destination used as the target --> <bean name="TargetDestinationFactory" class="org.hornetq.api.jms.bridge.impl.JNDIDestinationFactory"> <constructor> <parameter> <inject bean="JNDI" /> </parameter> <parameter>/queue/target</parameter> </constructor> </bean> <!-- JNDI is a Hashtable containing the JNDI properties required --> <!-- to connect to the sources and targets JMS resrouces --> <bean name="JNDI" class="java.util.Hashtable"> <constructor class="java.util.Map"> <map class="java.util.Hashtable" keyClass="String" valueClass="String"> <entry> <key>java.naming.factory.initial</key> <value>org.jnp.interfaces.NamingContextFactory</value> </entry> <entry> <key>java.naming.provider.url</key> <value>jnp://localhost:1099</value> </entry> <entry> <key>java.naming.factory.url.pkgs</key> <value>org.jboss.naming:org.jnp.interfaces"</value> </entry> <entry> <key>jnp.timeout</key> <value>5000</value> </entry> <entry> <key>jnp.sotimeout</key> <value>5000</value> </entry> </map> </constructor> </bean> <bean name="MBeanServer" class="javax.management.MBeanServer"> <constructor factoryClass="org.jboss.mx.util.MBeanServerLocator" factoryMethod="locateJBoss"/> </bean> </deployment>
The main bean deployed is the JMSBridge
bean. The bean is
configurable by the parameters passed to its constructor.
To let a parameter be unspecified (for example, if the authentication is
anonymous or no message selector is provided), use <null
/>
for the unspecified parameter value.
Source Connection Factory Factory
This injects the SourceCFF
bean (also defined in the
beans file). This bean is used to create the source
ConnectionFactory
Target Connection Factory Factory
This injects the TargetCFF
bean (also defined in the
beans file). This bean is used to create the target
ConnectionFactory
Source Destination Factory Factory
This injects the SourceDestinationFactory
bean (also
defined in the beans file). This bean is used to create the
source
Destination
Target Destination Factory Factory
This injects the TargetDestinationFactory
bean (also
defined in the beans file). This bean is used to create the
target
Destination
Source User Name
this parameter is the username for creating the source connection
Source Password
this parameter is the parameter for creating the source connection
Target User Name
this parameter is the username for creating the target connection
Target Password
this parameter is the password for creating the target connection
Selector
This represents a JMS selector expression used for consuming messages from the source destination. Only messages that match the selector expression will be bridged from the source to the target destination
The selector expression must follow the JMS selector syntax
Failure Retry Interval
This represents the amount of time in ms to wait between trying to recreate connections to the source or target servers when the bridge has detected they have failed
Max Retries
This represents the number of times to attempt to recreate connections to
the source or target servers when the bridge has detected they have failed.
The bridge will give up after trying this number of times. -1
represents 'try forever'
Quality Of Service
This parameter represents the desired quality of service mode
Possible values are:
AT_MOST_ONCE
DUPLICATES_OK
ONCE_AND_ONLY_ONCE
See Section 33.4, “Quality Of Service” for a explanation of these modes.
Max Batch Size
This represents the maximum number of messages to consume from the source
destination before sending them in a batch to the target destination. Its
value must >= 1
Max Batch Time
This represents the maximum number of milliseconds to wait before sending
a batch to target, even if the number of messages consumed has not reached
MaxBatchSize
. Its value must be -1
to represent 'wait forever', or >= 1
to specify an actual
time
Subscription Name
If the source destination represents a topic, and you want to consume from the topic using a durable subscription then this parameter represents the durable subscription name
Client ID
If the source destination represents a topic, and you want to consume from the topic using a durable subscription then this attribute represents the the JMS client ID to use when creating/looking up the durable subscription
Add MessageID In Header
If true
, then the original message's message ID will be
appended in the message sent to the destination in the header HORNETQ_BRIDGE_MSG_ID_LIST
. If the message is bridged more
than once, each message ID will be appended. This enables a distributed
request-response pattern to be used
when you receive the message you can send back a response using the correlation id of the first message id, so when the original sender gets it back it will be able to correlate it.
MBean Server
To manage the JMS Bridge using JMX, set the MBeanServer where the JMS Bridge MBean must be registered (e.g. the JVM Platform MBeanServer or JBoss AS MBeanServer)
ObjectName
If you set the MBeanServer, you also need to set the ObjectName used to register the JMS Bridge MBean (must be unique)
The source and target connection factory factories are used to create the connection factory used to create the connection for the source or target server.
The configuration example above uses the default implementation provided by
HornetQ that looks up the connection factory using JNDI. For other Application
Servers or JMS providers a new implementation may have to be provided. This can
easily be done by implementing the interface org.hornetq.jms.bridge.ConnectionFactoryFactory
.
Again, similarly, these are used to create or lookup up the destinations.
In the configuration example above, we have used the default provided by HornetQ that looks up the destination using JNDI.
A new implementation can be provided by implementing org.hornetq.jms.bridge.DestinationFactory
interface.
The quality of service modes used by the bridge are described here in more detail.
With this QoS mode messages will reach the destination from the source at most once. The messages are consumed from the source and acknowledged before sending to the destination. Therefore there is a possibility that if failure occurs between removing them from the source and them arriving at the destination they could be lost. Hence delivery will occur at most once.
This mode is available for both durable and non-durable messages.
With this QoS mode, the messages are consumed from the source and then acknowledged after they have been successfully sent to the destination. Therefore there is a possibility that if failure occurs after sending to the destination but before acknowledging them, they could be sent again when the system recovers. I.e. the destination might receive duplicates after a failure.
This mode is available for both durable and non-durable messages.
This QoS mode ensures messages will reach the destination from the source once and only once. (Sometimes this mode is known as "exactly once"). If both the source and the destination are on the same HornetQ server instance then this can be achieved by sending and acknowledging the messages in the same local transaction. If the source and destination are on different servers this is achieved by enlisting the sending and consuming sessions in a JTA transaction. The JTA transaction is controlled by JBoss Transactions JTA * implementation which is a fully recovering transaction manager, thus providing a very high degree of durability. If JTA is required then both supplied connection factories need to be XAConnectionFactory implementations. This is likely to be the slowest mode since it requires extra persistence for the transaction logging.
This mode is only available for durable messages.
For a specific application it may possible to provide once and only once semantics without using the ONCE_AND_ONLY_ONCE QoS level. This can be done by using the DUPLICATES_OK mode and then checking for duplicates at the destination and discarding them. Some JMS servers provide automatic duplicate message detection functionality, or this may be possible to implement on the application level by maintaining a cache of received message ids on disk and comparing received messages to them. The cache would only be valid for a certain period of time so this approach is not as watertight as using ONCE_AND_ONLY_ONCE but may be a good choice depending on your specific application.
There is a possibility that the target or source server will not be available at some point in time.
If this occurs then the bridge will try Max Retries
to reconnect every
Failure Retry Interval
milliseconds as specified in the JMS Bridge definition.
However since a third party JNDI is used, in this case the JBoss naming server, it is possible for the
JNDI lookup to hang if the network were to disappear during the JNDI lookup. To stop this occuring the JNDI
definition can be configured to time out if this occurs. To do this set the jnp.timeout
and the jnp.sotimeout
on the Initial Context definition. The first sets the connection
timeout for the initial connection and the second the read timeout for the socket.
Once the initial JNDI connection has succeeded all calls are made using RMI. If you want to control the timeouts for the RMI connections then this can be done via system properties. JBoss uses Sun's RMI and the properties can be found here. The default connection timeout is 10 seconds and the default read timeout is 18 seconds.
If you implement your own factories for looking up JMS resources then you will have to bear in mind timeout issues.
Please see Section 11.3.5, “JMS Bridge” which shows how to configure and use a JMS Bridge with JBoss AS to send messages to the source destination and consume them from the target destination.
Please see Section 11.1.28, “JMS Bridge” which shows how to configure and use a JMS Bridge between two standalone HornetQ servers.
HornetQ clients can be configured to automatically reconnect or re-attach to the server in the event that a failure is detected in the connection between the client and the server.
If the failure was due to some transient failure such as a temporary network failure, and the target server was not restarted, then the sessions will still be existent on the server, asssuming the client hasn't been disconnected for more than connection-ttl Chapter 17, Detecting Dead Connections.
In this scenario, HornetQ will automatically re-attach the client sessions to the server sessions when the connection reconnects. This is done 100% transparently and the client can continue exactly as if nothing had happened.
The way this works is as follows:
As HornetQ clients send commands to their servers they store each sent command in an in-memory buffer. In the case that connection failure occurs and the client subsequently reattaches to the same server, as part of the reattachment protocol the server informs the client during reattachment with the id of the last command it successfully received from that client.
If the client has sent more commands than were received before failover it can replay any sent commands from its buffer so that the client and server can reconcile their states.
The size of this buffer is configured by the ConfirmationWindowSize
parameter, when the server has received ConfirmationWindowSize
bytes
of commands and processed them it will send back a command confirmation to the client,
and the client can then free up space in the buffer.
If you are using JMS and you're using the JMS service on the server to load your JMS
connection factory instances into JNDI then this parameter can be configured in hornetq-jms.xml
using the element confirmation-window-size
a. If you're using JMS but not using JNDI then
you can set these values directly on the HornetQConnectionFactory
instance using the appropriate setter method.
If you're using the core API you can set these values directly on the ServerLocator
instance using the appropriate setter method.
The window is specified in bytes.
Setting this parameter to -1
disables any buffering and prevents
any re-attachment from occurring, forcing reconnect instead. The default value for this
parameter is -1
. (Which means by default no auto re-attachment will occur)
Alternatively, the server might have actually been restarted after crashing or being stopped. In this case any sessions will no longer be existent on the server and it won't be possible to 100% transparently re-attach to them.
In this case, HornetQ will automatically reconnect the connection and recreate any sessions and consumers on the server corresponding to the sessions and consumers on the client. This process is exactly the same as what happens during failover onto a backup server.
Client reconnection is also used internally by components such as core bridges to allow them to reconnect to their target servers.
Please see the section on failover Section 39.2.1, “Automatic Client Failover” to get a full understanding of how transacted and non-transacted sessions are reconnected during failover/reconnect and what you need to do to maintain once and only once delivery guarantees.
Client reconnection is configured using the following parameters:
retry-interval
. This optional parameter determines the
period in milliseconds between subsequent reconnection attempts, if the
connection to the target server has failed. The default value is 2000
milliseconds.
retry-interval-multiplier
. This optional parameter
determines determines a multiplier to apply to the time since the last retry to
compute the time to the next retry.
This allows you to implement an exponential backoff between retry attempts.
Let's take an example:
If we set retry-interval
to 1000
ms and
we set retry-interval-multiplier
to 2.0
,
then, if the first reconnect attempt fails, we will wait 1000
ms then 2000
ms then 4000
ms between
subsequent reconnection attempts.
The default value is 1.0
meaning each reconnect attempt is
spaced at equal intervals.
max-retry-interval
. This optional parameter determines the
maximum retry interval that will be used. When setting retry-interval-multiplier
it would otherwise be possible that
subsequent retries exponentially increase to ridiculously large values. By
setting this parameter you can set an upper limit on that value. The default
value is 2000
milliseconds.
reconnect-attempts
. This optional parameter determines the
total number of reconnect attempts to make before giving up and shutting down. A
value of -1
signifies an unlimited number of attempts. The
default value is 0
.
If you're using JMS, and you're using the JMS Service on the server to load your JMS
connection factory instances directly into JNDI, then you can specify these parameters
in the xml configuration in hornetq-jms.xml
, for example:
<connection-factory name="ConnectionFactory"> <connectors> <connector-ref connector-name="netty"/> </connectors> <entries> <entry name="ConnectionFactory"/> <entry name="XAConnectionFactory"/> </entries> <retry-interval>1000</retry-interval> <retry-interval-multiplier>1.5</retry-interval-multiplier> <max-retry-interval>60000</max-retry-interval> <reconnect-attempts>1000</reconnect-attempts> </connection-factory>
If you're using JMS, but instantiating your JMS connection factory directly, you can
specify the parameters using the appropriate setter methods on the HornetQConnectionFactory
immediately after creating it.
If you're using the core API and instantiating the ServerLocator
instance directly you can also specify the
parameters using the appropriate setter methods on the ServerLocator
immediately after creating it.
If your client does manage to reconnect but the session is no longer available on the
server, for instance if the server has been restarted or it has timed out, then the
client won't be able to re-attach, and any ExceptionListener
or
FailureListener
instances registered on the connection or session
will be called.
HornetQ allows you to configure objects called diverts with some simple server configuration.
Diverts allow you to transparently divert messages routed to one address to some other address, without making any changes to any client application logic.
Diverts can be exclusive, meaning that the message is diverted to the new address, and does not go to the old address at all, or they can be non-exclusive which means the message continues to go the old address, and a copy of it is also sent to the new address. Non-exclusive diverts can therefore be used for splitting message flows, e.g. there may be a requirement to monitor every order sent to an order queue.
Diverts can also be configured to have an optional message filter. If specified then only messages that match the filter will be diverted.
Diverts can also be configured to apply a Transformer
. If specified,
all diverted messages will have the opportunity of being transformed by the Transformer
.
A divert will only divert a message to an address on the same server, however, if you want to divert to an address on a different server, a common pattern would be to divert to a local store-and-forward queue, then set up a bridge which consumes from that queue and forwards to an address on a different server.
Diverts are therefore a very sophisticated concept, which when combined with bridges can be used to create interesting and complex routings. The set of diverts on a server can be thought of as a type of routing table for messages. Combining diverts with bridges allows you to create a distributed network of reliable routing connections between multiple geographically distributed servers, creating your global messaging mesh.
Diverts are defined as xml in the hornetq-configuration.xml
file. There can
be zero or more diverts in the file.
Please see Section 11.1.18, “Divert” for a full working example showing you how to configure and use diverts.
Let's take a look at some divert examples:
Let's take a look at an exclusive divert. An exclusive divert diverts all matching messages that are routed to the old address to the new address. Matching messages do not get routed to the old address.
Here's some example xml configuration for an exclusive divert, it's taken from the divert example:
<divert name="prices-divert"> <address>jms.topic.priceUpdates</address> <forwarding-address>jms.queue.priceForwarding</forwarding-address> <filter string="office='New York'"/> <transformer-class-name> org.hornetq.jms.example.AddForwardingTimeTransformer </transformer-class-name> <exclusive>true</exclusive> </divert>
We define a divert called 'prices-divert
' that will divert any
messages sent to the address 'jms.topic.priceUpdates
' (this
corresponds to any messages sent to a JMS Topic called 'priceUpdates
') to another local address 'jms.queue.priceForwarding
' (this corresponds to a local JMS queue called
'priceForwarding
'
We also specify a message filter string so only messages with the message property
office
with value New York
will get diverted,
all other messages will continue to be routed to the normal address. The filter string
is optional, if not specified then all messages will be considered matched.
In this example a transformer class is specified. Again this is optional, and if specified the transformer will be executed for each matching message. This allows you to change the messages body or properties before it is diverted. In this example the transformer simply adds a header that records the time the divert happened.
This example is actually diverting messages to a local store and forward queue, which is configured with a bridge which forwards the message to an address on another HornetQ server. Please see the example for more details.
Now we'll take a look at a non-exclusive divert. Non exclusive diverts are the same as exclusive diverts, but they only forward a copy of the message to the new address. The original message continues to the old address
You can therefore think of non-exclusive diverts as splitting a message flow.
Non exclusive diverts can be configured in the same way as exclusive diverts with an optional filter and transformer, here's an example non-exclusive divert, again from the divert example:
<divert name="order-divert"> <address>jms.queue.orders</address> <forwarding-address>jms.topic.spyTopic</forwarding-address> <exclusive>false</exclusive> </divert>
The above divert example takes a copy of every message sent to the address 'jms.queue.orders
' (Which corresponds to a JMS Queue called 'orders
') and sends it to a local address called 'jms.topic.SpyTopic
' (which corresponds to a JMS Topic called 'SpyTopic
').
The function of a bridge is to consume messages from a source queue, and forward them to a target address, typically on a different HornetQ server.
The source and target servers do not have to be in the same cluster which makes bridging suitable for reliably sending messages from one cluster to another, for instance across a WAN, or internet and where the connection may be unreliable.
The bridge has built in resilience to failure so if the target server connection is lost, e.g. due to network failure, the bridge will retry connecting to the target until it comes back online. When it comes back online it will resume operation as normal.
In summary, bridges are a way to reliably connect two separate HornetQ servers together. With a core bridge both source and target servers must be HornetQ servers.
Bridges can be configured to provide once and only once delivery guarantees even in the event of the failure of the source or the target server. They do this by using duplicate detection (described in Chapter 37, Duplicate Message Detection).
Although they have similar function, don't confuse core bridges with JMS bridges!
Core bridges are for linking a HornetQ node with another HornetQ node and do not use the JMS API. A JMS Bridge is used for linking any two JMS 1.1 compliant JMS providers. So, a JMS Bridge could be used for bridging to or from different JMS compliant messaging system. It's always preferable to use a core bridge if you can. Core bridges use duplicate detection to provide once and only once guarantees. To provide the same guarantee using a JMS bridge you would have to use XA which has a higher overhead and is more complex to configure.
Bridges are configured in hornetq-configuration.xml
. Let's kick off
with an example (this is actually from the bridge example):
<bridge name="my-bridge"> <queue-name>jms.queue.sausage-factory</queue-name> <forwarding-address>jms.queue.mincing-machine</forwarding-address> <filter-string="name='aardvark'"/> <transformer-class-name> org.hornetq.jms.example.HatColourChangeTransformer </transformer-class-name> <retry-interval>1000</retry-interval> <ha>true</ha> <retry-interval-multiplier>1.0</retry-interval-multiplier> <reconnect-attempts>-1</reconnect-attempts> <failover-on-server-shutdown>false</failover-on-server-shutdown> <use-duplicate-detection>true</use-duplicate-detection> <confirmation-window-size>10000000</confirmation-window-size> <connector-ref connector-name="remote-connector" backup-connector-name="backup-remote-connector"/> <user>foouser</user> <password>foopassword</password> </bridge>
In the above example we have shown all the parameters its possible to configure for a bridge. In practice you might use many of the defaults so it won't be necessary to specify them all explicitly.
Let's take a look at all the parameters in turn:
name
attribute. All bridges must have a unique name in the
server.
queue-name
. This is the unique name of the local queue that
the bridge consumes from, it's a mandatory parameter.
The queue must already exist by the time the bridge is instantiated at start-up.
If you're using JMS then normally the JMS configuration hornetq-jms.xml
is loaded after the core configuration file
hornetq-configuration.xml
is loaded. If your bridge
is consuming from a JMS queue then you'll need to make sure the JMS queue is
also deployed as a core queue in the core configuration. Take a look at the
bridge example for an example of how this is done.
forwarding-address
. This is the address on the target
server that the message will be forwarded to. If a forwarding address is not
specified, then the original address of the message will be retained.
filter-string
. An optional filter string can be supplied.
If specified then only messages which match the filter expression specified in
the filter string will be forwarded. The filter string follows the HornetQ
filter expression syntax described in Chapter 14, Filter Expressions.
transformer-class-name
. An optional transformer-class-name
can be specified. This is the name of a user-defined class which implements the
org.hornetq.core.server.cluster.Transformer
interface.
If this is specified then the transformer's transform()
method will be invoked with the message before it is forwarded. This gives you
the opportunity to transform the message's header or body before forwarding
it.
ha
. This optional parameter determines whether or not this
bridge should support high availability. True means it will connect to any available
server in a cluster and support failover. The default value is false
.
retry-interval
. This optional parameter determines the
period in milliseconds between subsequent reconnection attempts, if the
connection to the target server has failed. The default value is 2000
milliseconds.
retry-interval-multiplier
. This optional parameter
determines determines a multiplier to apply to the time since the last retry to
compute the time to the next retry.
This allows you to implement an exponential backoff between retry attempts.
Let's take an example:
If we set retry-interval
to 1000
ms and
we set retry-interval-multiplier
to 2.0
,
then, if the first reconnect attempt fails, we will wait 1000
ms then 2000
ms then 4000
ms between
subsequent reconnection attempts.
The default value is 1.0
meaning each reconnect attempt is
spaced at equal intervals.
reconnect-attempts
. This optional parameter determines the
total number of reconnect attempts the bridge will make before giving up and
shutting down. A value of -1
signifies an unlimited number of
attempts. The default value is -1
.
failover-on-server-shutdown
. This optional parameter
determines whether the bridge will attempt to failover onto a backup server (if
specified) when the target server is cleanly shutdown rather than
crashed.
The bridge connector can specify both a live and a backup server, if it
specifies a backup server and this parameter is set to true
then if the target server is cleanly shutdown the bridge
connection will attempt to failover onto its backup. If the bridge connector has
no backup server configured then this parameter has no effect.
Sometimes you want a bridge configured with a live and a backup target server, but you don't want to failover to the backup if the live server is simply taken down temporarily for maintenance, this is when this parameter comes in handy.
The default value for this parameter is false
.
use-duplicate-detection
. This optional parameter determines
whether the bridge will automatically insert a duplicate id property into each
message that it forwards.
Doing so, allows the target server to perform duplicate detection on messages it receives from the source server. If the connection fails or server crashes, then, when the bridge resumes it will resend unacknowledged messages. This might result in duplicate messages being sent to the target server. By enabling duplicate detection allows these duplicates to be screened out and ignored.
This allows the bridge to provide a once and only once delivery guarantee without using heavyweight methods such as XA (see Chapter 37, Duplicate Message Detection for more information).
The default value for this parameter is true
.
confirmation-window-size
. This optional parameter
determines the confirmation-window-size
to use for the
connection used to forward messages to the target node. This attribute is
described in section Chapter 34, Client Reconnection and Session Reattachment
max-size-bytes
to prevent the flow of
messages from ceasing.
connector-ref
. This mandatory parameter determines which
connector pair the bridge will use to actually make the
connection to the target server.
A connector encapsulates knowledge of what transport to use (TCP, SSL, HTTP etc) as well as the server connection parameters (host, port etc). For more information about what connectors are and how to configure them, please see Chapter 16, Configuring the Transport.
The connector-ref
element can be configured with two
attributes:
connector-name
. This references the name of a
connector defined in the core configuration file hornetq-configuration.xml
. The bridge will use this
connector to make its connection to the target server. This attribute is
mandatory.
backup-connector-name
. This optional parameter also
references the name of a connector defined in the core configuration
file hornetq-configuration.xml
. It represents the
connector that the bridge will fail-over onto if it detects the live
server connection has failed. If this is specified and failover-on-server-shutdown
is set to true
then it will also attempt failover onto this
connector if the live target server is cleanly shut-down.
user
. This optional parameter determines the user name to
use when creating the bridge connection to the remote server. If it is not
specified the default cluster user specified by cluster-user
in hornetq-configuration.xml
will be used.
password
. This optional parameter determines the password
to use when creating the bridge connection to the remote server. If it is not
specified the default cluster password specified by cluster-password
in hornetq-configuration.xml
will be used.
HornetQ includes powerful automatic duplicate message detection, filtering out duplicate messages without you having to code your own fiddly duplicate detection logic at the application level. This chapter will explain what duplicate detection is, how HornetQ uses it and how and where to configure it.
When sending messages from a client to a server, or indeed from a server to another server, if the target server or connection fails sometime after sending the message, but before the sender receives a response that the send (or commit) was processed successfully then the sender cannot know for sure if the message was sent successfully to the address.
If the target server or connection failed after the send was received and processed but before the response was sent back then the message will have been sent to the address successfully, but if the target server or connection failed before the send was received and finished processing then it will not have been sent to the address successfully. From the senders point of view it's not possible to distinguish these two cases.
When the server recovers this leaves the client in a difficult situation. It knows the target server failed, but it does not know if the last message reached its destination ok. If it decides to resend the last message, then that could result in a duplicate message being sent to the address. If each message was an order or a trade then this could result in the order being fulfilled twice or the trade being double booked. This is clearly not a desirable situation.
Sending the message(s) in a transaction does not help out either. If the server or connection fails while the transaction commit is being processed it is also indeterminate whether the transaction was successfully committed or not!
To solve these issues HornetQ provides automatic duplicate messages detection for messages sent to addresses.
Enabling duplicate message detection for sent messages is simple: you just need to set a special property on the message to a unique value. You can create the value however you like, as long as it is unique. When the target server receives the message it will check if that property is set, if it is, then it will check in its in memory cache if it has already received a message with that value of the header. If it has received a message with the same value before then it will ignore the message.
Using duplicate detection to move messages between nodes can give you the same once and only once delivery guarantees as if you were using an XA transaction to consume messages from source and send them to the target, but with less overhead and much easier configuration than using XA.
If you're sending messages in a transaction then you don't have to set the property for every message you send in that transaction, you only need to set it once in the transaction. If the server detects a duplicate message for any message in the transaction, then it will ignore the entire transaction.
The name of the property that you set is given by the value of org.hornetq.api.core.HDR_DUPLICATE_DETECTION_ID
, which
is _HQ_DUPL_ID
The value of the property can be of type byte[]
or SimpleString
if you're using the core API. If you're using JMS it must be
a String
, and its value should be unique. An easy way of generating
a unique id is by generating a UUID.
Here's an example of setting the property using the core API:
... ClientMessage message = session.createMessage(true); SimpleString myUniqueID = "This is my unique id"; // Could use a UUID for this message.setStringProperty(HDR_DUPLICATE_DETECTION_ID, myUniqueID); ...
And here's an example using the JMS API:
... Message jmsMessage = session.createMessage(); String myUniqueID = "This is my unique id"; // Could use a UUID for this message.setStringProperty(HDR_DUPLICATE_DETECTION_ID.toString(), myUniqueID); ...
The server maintains caches of received values of the org.hornetq.core.message.impl.HDR_DUPLICATE_DETECTION_ID
property
sent to each address. Each address has its own distinct cache.
The cache is a circular fixed size cache. If the cache has a maximum size of n
elements, then the n + 1
th id stored will overwrite
the 0
th element in the cache.
The maximum size of the cache is configured by the parameter id-cache-size
in hornetq-configuration.xml
, the default
value is 2000
elements.
The caches can also be configured to persist to disk or not. This is configured by the
parameter persist-id-cache
, also in hornetq-configuration.xml
. If this is set to true
then
each id will be persisted to permanent storage as they are received. The default value
for this parameter is true
.
When choosing a size of the duplicate id cache be sure to set it to a larger enough size so if you resend messages all the previously sent ones are in the cache not having been overwritten.
Core bridges can be configured to automatically add a unique duplicate id value (if there isn't already one in the message) before forwarding the message to it's target. This ensures that if the target server crashes or the connection is interrupted and the bridge resends the message, then if it has already been received by the target server, it will be ignored.
To configure a core bridge to add the duplicate id header, simply set the use-duplicate-detection
to true
when configuring a
bridge in hornetq-configuration.xml
.
The default value for this parameter is true
.
For more information on core bridges and how to configure them, please see Chapter 36, Core Bridges.
Cluster connections internally use core bridges to move messages reliable between nodes of the cluster. Consequently they can also be configured to insert the duplicate id header for each message they move using their internal bridges.
To configure a cluster connection to add the duplicate id header, simply set the
use-duplicate-detection
to true
when
configuring a cluster connection in hornetq-configuration.xml
.
The default value for this parameter is true
.
For more information on cluster connections and how to configure them, please see Chapter 38, Clusters.
HornetQ clusters allow groups of HornetQ servers to be grouped together in order to share message processing load. Each active node in the cluster is an active HornetQ server which manages its own messages and handles its own connections.
The cluster is formed by each node declaring cluster connections
to other nodes in the core configuration file hornetq-configuration.xml
. When a node forms a cluster connection to
another node, internally it creates a core bridge (as described in
Chapter 36, Core Bridges) connection between it and the other node, this is
done transparently behind the scenes - you don't have to declare an explicit bridge for
each node. These cluster connections allow messages to flow between the nodes of the
cluster to balance load.
Nodes can be connected together to form a cluster in many different topologies, we will discuss a couple of the more common topologies later in this chapter.
We'll also discuss client side load balancing, where we can balance client connections across the nodes of the cluster, and we'll consider message redistribution where HornetQ will redistribute messages between nodes to avoid starvation.
Another important part of clustering is server discovery where servers can broadcast their connection details so clients or other servers can connect to them with the minimum of configuration.
Once a cluster node has been configured it is common to simply copy that configuration
to other nodes to produce a symmetric cluster. However, care must be taken when copying the
HornetQ files. Do not copy the HornetQ data (i.e. the
bindings
, journal
, and large-messages
directories) from one node to another. When a node is started for the first time and initializes
its journal files it also persists a special identifier to the journal
directory. This id must be unique among nodes in the cluster or the
cluster will not form properly.
Server discovery is a mechanism by which servers can propagate their connection details to:
Messaging clients. A messaging client wants to be able to connect to the servers of the cluster without having specific knowledge of which servers in the cluster are up at any one time.
Other servers. Servers in a cluster want to be able to create cluster connections to each other without having prior knowledge of all the other servers in the cluster.
This information, lets call it the Cluster Topology, is actually sent around normal HornetQ connections to clients and to other servers over cluster connections. This being the case we need a way of establishing the initial first connection. This can be done using dynamic discovery techniques like UDP and JGroups, or by providing a list of initial connectors.
Server discovery uses UDP multicast or JGroups to broadcast server connection settings.
A broadcast group is the means by which a server broadcasts connectors over the network. A connector defines a way in which a client (or other server) can make connections to the server. For more information on what a connector is, please see Chapter 16, Configuring the Transport.
The broadcast group takes a set of connector pairs, each connector pair contains connection settings for a live and backup server (if one exists) and broadcasts them on the network. Depending on which broadcasting technique you configure the cluster, it uses either UDP or JGroups to broadcast connector pairs information.
Broadcast groups are defined in the server configuration file hornetq-configuration.xml
. There can be many broadcast groups per
HornetQ server. All broadcast groups must be defined in a broadcast-groups
element.
Let's take a look at an example broadcast group from hornetq-configuration.xml
that defines a UDP broadcast group:
<broadcast-groups> <broadcast-group name="my-broadcast-group"> <local-bind-address>172.16.9.3</local-bind-address> <local-bind-port>5432</local-bind-port> <group-address>231.7.7.7</group-address> <group-port>9876</group-port> <broadcast-period>2000</broadcast-period> <connector-ref connector-name="netty-connector"/> </broadcast-group> </broadcast-groups>
Some of the broadcast group parameters are optional and you'll normally use the defaults, but we specify them all in the above example for clarity. Let's discuss each one in turn:
name
attribute. Each broadcast group in the server must
have a unique name.
local-bind-address
. This is the local bind address that
the datagram socket is bound to. If you have multiple network interfaces on
your server, you would specify which one you wish to use for broadcasts by
setting this property. If this property is not specified then the socket
will be bound to the wildcard address, an IP address chosen by the
kernel. This is a UDP specific attribute.
local-bind-port
. If you want to specify a local port to
which the datagram socket is bound you can specify it here. Normally you
would just use the default value of -1
which signifies
that an anonymous port should be used. This parameter is alawys specified in conjunction with
local-bind-address
. This is a UDP specific attribute.
group-address
. This is the multicast address to which
the data will be broadcast. It is a class D IP address in the range 224.0.0.0
to 239.255.255.255
, inclusive.
The address 224.0.0.0
is reserved and is not available
for use. This parameter is mandatory. This is a UDP specific attribute.
group-port
. This is the UDP port number used for
broadcasting. This parameter is mandatory. This is a UDP specific attribute.
broadcast-period
. This is the period in milliseconds
between consecutive broadcasts. This parameter is optional, the default
value is 2000
milliseconds.
connector-ref
. This specifies the connector and
optional backup connector that will be broadcasted (see Chapter 16, Configuring the Transport for more information on connectors).
The connector to be broadcasted is specified by the connector-name
attribute.
Here is another example broadcast group that defines a JGroups broadcast group:
<broadcast-groups> <broadcast-group name="my-broadcast-group"> <jgroups-file>test-jgroups-file_ping.xml</jgroups-file> <jgroups-channel>hornetq_broadcast_channel</jgroups-channel> <broadcast-period>2000</broadcast-period> <connector-ref connector-name="netty-connector"/> </broadcast-group> </broadcast-groups>
To be able to use JGroups to broadcast, one must specify two attributes, i.e.
jgroups-file
and jgroups-channel
, as discussed
in details as following:
jgroups-file
attribute. This is the name of JGroups configuration
file. It will be used to initialize JGroups channels. Make sure the file is in the
java resource path so that HornetQ can load it.
jgroups-channel
attribute. The name that JGroups channels connect
to for broadcasting.
The JGroups attributes (jgroups-file
and jgroups-channel
)
and UDP specific attributes described above are exclusive of each other. Only one set can be
specified in a broadcast group configuration. Don't mix them!
The following is an example of a JGroups file
<config xmlns="urn:org:jgroups" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="urn:org:jgroups http://www.jgroups.org/schema/JGroups-3.0.xsd"> <TCP loopback="true" recv_buf_size="20000000" send_buf_size="640000" discard_incompatible_packets="true" max_bundle_size="64000" max_bundle_timeout="30" enable_bundling="true" use_send_queues="false" sock_conn_timeout="300" thread_pool.enabled="true" thread_pool.min_threads="1" thread_pool.max_threads="10" thread_pool.keep_alive_time="5000" thread_pool.queue_enabled="false" thread_pool.queue_max_size="100" thread_pool.rejection_policy="run" oob_thread_pool.enabled="true" oob_thread_pool.min_threads="1" oob_thread_pool.max_threads="8" oob_thread_pool.keep_alive_time="5000" oob_thread_pool.queue_enabled="false" oob_thread_pool.queue_max_size="100" oob_thread_pool.rejection_policy="run"/> <FILE_PING location="../file.ping.dir"/> <MERGE2 max_interval="30000" min_interval="10000"/> <FD_SOCK/> <FD timeout="10000" max_tries="5" /> <VERIFY_SUSPECT timeout="1500" /> <BARRIER /> <pbcast.NAKACK use_mcast_xmit="false" retransmit_timeout="300,600,1200,2400,4800" discard_delivered_msgs="true"/> <UNICAST timeout="300,600,1200" /> <pbcast.STABLE stability_delay="1000" desired_avg_gossip="50000" max_bytes="400000"/> <pbcast.GMS print_local_addr="true" join_timeout="3000" view_bundling="true"/> <FC max_credits="2000000" min_threshold="0.10"/> <FRAG2 frag_size="60000" /> <pbcast.STATE_TRANSFER/> <pbcast.FLUSH timeout="0"/> </config>
As it shows, the file content defines a jgroups protocol stacks. If you want hornetq
to use this stacks for channel creation, you have to make sure the value of
jgroups-file
in your broadcast-group/discovery-group configuration
to be the name of this jgroups configuration file. For example if the above stacks
configuration is stored in a file named "jgroups-stacks.xml" then your
jgroups-file
should be like
<jgroups-file>jgroups-stacks.xml</jgroups-file>
While the broadcast group defines how connector information is broadcasted from a server, a discovery group defines how connector information is received from a broadcast endpoint (a UDP multicast address or JGroup channel).
A discovery group maintains a list of connector pairs - one for each broadcast by a different server. As it receives broadcasts on the broadcast endpoint from a particular server it updates its entry in the list for that server.
If it has not received a broadcast from a particular server for a length of time it will remove that server's entry from its list.
Discovery groups are used in two places in HornetQ:
By cluster connections so they know how to obtain an initial connection to download the topology
By messaging clients so they know how to obtain an initial connection to download the topology
Although a discovery group will always accept broadcasts, its current list of avaliable live and backup servers is only ever used when an initial connection is made, from then server discovery is done over the normal HornetQ connections.
Each discovery group must be configured with broadcast endpoint (UDP or JGroups) that matches its broadcast group counterpart. For example, if broadcast is configured using UDP, the discovery group must also use UDP, and the same multicast address.
For cluster connections, discovery groups are defined in the server side
configuration file hornetq-configuration.xml
. All discovery
groups must be defined inside a discovery-groups
element. There
can be many discovery groups defined by HornetQ server. Let's look at an
example:
<discovery-groups> <discovery-group name="my-discovery-group"> <local-bind-address>172.16.9.7</local-bind-address> <group-address>231.7.7.7</group-address> <group-port>9876</group-port> <refresh-timeout>10000</refresh-timeout> </discovery-group> </discovery-groups>
We'll consider each parameter of the discovery group:
name
attribute. Each discovery group must have a unique
name per server.
local-bind-address
. If you are running with multiple network interfaces on the same machine, you
may want to specify that the discovery group listens only only a specific interface. To do this you can specify the interface
address with this parameter. This parameter is optional. This is a UDP specific attribute.
group-address
. This is the multicast ip address of the
group to listen on. It should match the group-address
in
the broadcast group that you wish to listen from. This parameter is
mandatory. This is a UDP specific attribute.
group-port
. This is the UDP port of the multicast
group. It should match the group-port
in the broadcast
group that you wish to listen from. This parameter is mandatory. This is a UDP specific attribute.
refresh-timeout
. This is the period the discovery group
waits after receiving the last broadcast from a particular server before
removing that servers connector pair entry from its list. You would normally
set this to a value significantly higher than the broadcast-period
on the broadcast group otherwise servers
might intermittently disappear from the list even though they are still
broadcasting due to slight differences in timing. This parameter is
optional, the default value is 10000
milliseconds (10
seconds).
Here is another example that defines a JGroups discovery group:
<discovery-groups> <discovery-group name="my-broadcast-group"> <jgroups-file>test-jgroups-file_ping.xml</jgroups-file> <jgroups-channel>hornetq_broadcast_channel</jgroups-channel> <refresh-timeout>10000</refresh-timeout> </discovery-group> </discovery-groups>
To receive broadcast from JGroups channels, one must specify two attributes,
jgroups-file
and jgroups-channel
, as discussed
in details as following:
jgroups-file
attribute. This is the name of JGroups configuration
file. It will be used to initialize JGroups channels. Make sure the file is in the
java resource path so that HornetQ can load it.
jgroups-channel
attribute. The name that JGroups channels connect
to for receiving broadcasts.
The JGroups attributes (jgroups-file
and jgroups-channel
)
and UDP specific attributes described above are exclusive of each other. Only one set can be
specified in a discovery group configuration. Don't mix them!
Let's discuss how to configure a HornetQ client to use discovery to discover a list of servers to which it can connect. The way to do this differs depending on whether you're using JMS or the core API.
If you're using JMS and you're also using the JMS Service on the server to
load your JMS connection factory instances into JNDI, then you can specify which
discovery group to use for your JMS connection factory in the server side xml
configuration hornetq-jms.xml
. Let's take a look at an
example:
<connection-factory name="ConnectionFactory"> <discovery-group-ref discovery-group-name="my-discovery-group"/> <entries> <entry name="ConnectionFactory"/> </entries> </connection-factory>
The element discovery-group-ref
specifies the name of a
discovery group defined in hornetq-configuration.xml
.
When this connection factory is downloaded from JNDI by a client application and JMS connections are created from it, those connections will be load-balanced across the list of servers that the discovery group maintains by listening on the multicast address specified in the discovery group configuration.
If you're using JMS, but you're not using JNDI to lookup a connection factory - you're instantiating the JMS connection factory directly then you can specify the discovery group parameters directly when creating the JMS connection factory. Here's an example:
final String groupAddress = "231.7.7.7"; final int groupPort = 9876; ConnectionFactory jmsConnectionFactory = HornetQJMSClient.createConnectionFactory(new DiscoveryGroupConfiguration(groupAddress, groupPort), , JMSFactoryType.CF); Connection jmsConnection1 = jmsConnectionFactory.createConnection(); Connection jmsConnection2 = jmsConnectionFactory.createConnection();
The refresh-timeout
can be set directly on the DiscoveryGroupConfiguration
by using the setter method setDiscoveryRefreshTimeout()
if you
want to change the default value.
There is also a further parameter settable on the DiscoveryGroupConfiguration using the
setter method setDiscoveryInitialWaitTimeout()
. If the connection
factory is used immediately after creation then it may not have had enough time
to received broadcasts from all the nodes in the cluster. On first usage, the
connection factory will make sure it waits this long since creation before
creating the first connection. The default value for this parameter is 10000
milliseconds.
If you're using the core API to directly instantiate
ClientSessionFactory
instances, then you can specify the
discovery group parameters directly when creating the session factory. Here's an
example:
final String groupAddress = "231.7.7.7"; final int groupPort = 9876; ServerLocator factory = HornetQClient.createServerLocatorWithHA(new DiscoveryGroupConfiguration(groupAddress, groupPort)); ClientSessionFactory factory = locator.createSessionFactory(); ClientSession session1 = factory.createSession(); ClientSession session2 = factory.createSession();
The refresh-timeout
can be set directly on the DiscoveryGroupConfiguration
by using the setter method setDiscoveryRefreshTimeout()
if you
want to change the default value.
There is also a further parameter settable on the DiscoveryGroupConfiguration using the
setter method setDiscoveryInitialWaitTimeout()
. If the session factory
is used immediately after creation then it may not have had enough time to
received broadcasts from all the nodes in the cluster. On first usage, the
session factory will make sure it waits this long since creation before creating
the first session. The default value for this parameter is 10000
milliseconds.
Sometimes it may be impossible to use UDP on the network you are using. In this case its possible to configure a connection with an initial list if possible servers. This could be just one server that you know will always be available or a list of servers where at least one will be available.
This doesn't mean that you have to know where all your servers are going to be hosted, you can configure these servers to use the reliable servers to connect to. Once they are connected there connection details will be propagated via the server it connects to
For cluster connections there is no extra configuration needed, you just need to make sure that any connectors are defined in the usual manner, (see Chapter 16, Configuring the Transport for more information on connectors). These are then referenced by the cluster connection configuration.
A static list of possible servers can also be used by a normal client.
If you're using JMS and you're also using the JMS Service on the server to
load your JMS connection factory instances into JNDI, then you can specify which
connectors to use for your JMS connection factory in the server side xml
configuration hornetq-jms.xml
. Let's take a look at an
example:
<connection-factory name="ConnectionFactory"> <connectors> <connector-ref connector-name="netty-connector"/> <connector-ref connector-name="netty-connector2"/> <connector-ref connector-name="netty-connector3"/> </connectors> <entries> <entry name="ConnectionFactory"/> </entries> </connection-factory>
The element connectors
contains a list of pre defined connectors in the
hornetq-configuration.xml
file. When this connection factory is downloaded
from JNDI by a client application and JMS connections are created from it, those connections will
be load-balanced across the list of servers defined by these connectors.
If you're using JMS, but you're not using JNDI to lookup a connection factory - you're instantiating the JMS connection factory directly then you can specify the connector list directly when creating the JMS connection factory. Here's an example:
HashMap<String, Object> map = new HashMap<String, Object>(); map.put("host", "myhost"); map.put("port", "5445"); TransportConfiguration server1 = new TransportConfiguration(NettyConnectorFactory.class.getName(), map); HashMap<String, Object> map2 = new HashMap<String, Object>(); map2.put("host", "myhost2"); map2.put("port", "5446"); TransportConfiguration server2 = new TransportConfiguration(NettyConnectorFactory.class.getName(), map2); HornetQConnectionFactory cf = HornetQJMSClient.createConnectionFactoryWithHA(JMSFactoryType.CF, server1, server2);
If you are using the core API then the same can be done as follows:
HashMap<String, Object> map = new HashMap<String, Object>(); map.put("host", "myhost"); map.put("port", "5445"); TransportConfiguration server1 = new TransportConfiguration(NettyConnectorFactory.class.getName(), map); HashMap<String, Object> map2 = new HashMap<String, Object>(); map2.put("host", "myhost2"); map2.put("port", "5446"); TransportConfiguration server2 = new TransportConfiguration(NettyConnectorFactory.class.getName(), map2); ServerLocator locator = HornetQClient.createServerLocatorWithHA(server1, server2); ClientSessionFactory factory = locator.createSessionFactory(); ClientSession session = factory.createSession();
If cluster connections are defined between nodes of a cluster, then HornetQ will load balance messages arriving at a particular node from a client.
Let's take a simple example of a cluster of four nodes A, B, C, and D arranged in a
symmetric cluster (described in
Section 38.7.1, “Symmetric cluster”). We have a queue called OrderQueue
deployed on each node of the cluster.
We have client Ca connected to node A, sending orders to the server. We have also have
order processor clients Pa, Pb, Pc, and Pd connected to each of the nodes A, B, C, D. If
no cluster connection was defined on node A, then as order messages arrive on node A
they will all end up in the OrderQueue
on node A, so will only get
consumed by the order processor client attached to node A, Pa.
If we define a cluster connection on node A, then as ordered messages arrive on node A
instead of all of them going into the local OrderQueue
instance, they
are distributed in a round-robin fashion between all the nodes of the cluster. The
messages are forwarded from the receiving node to other nodes of the cluster. This is
all done on the server side, the client maintains a single connection to node A.
For example, messages arriving on node A might be distributed in the following order between the nodes: B, D, C, A, B, D, C, A, B, D. The exact order depends on the order the nodes started up, but the algorithm used is round robin.
HornetQ cluster connections can be configured to always blindly load balance messages in a round robin fashion irrespective of whether there are any matching consumers on other nodes, but they can be a bit cleverer than that and also be configured to only distribute to other nodes if they have matching consumers. We'll look at both these cases in turn with some examples, but first we'll discuss configuring cluster connections in general.
Cluster connections group servers into clusters so that messages can be load
balanced between the nodes of the cluster. Let's take a look at a typical cluster
connection. Cluster connections are always defined in hornetq-configuration.xml
inside a cluster-connection
element. There can be zero or more cluster
connections defined per HornetQ server.
<cluster-connections> <cluster-connection name="my-cluster"> <address>jms</address> <retry-interval>500</retry-interval> <use-duplicate-detection>true</use-duplicate-detection> <forward-when-no-consumers>false</forward-when-no-consumers> <max-hops>1</max-hops> <discovery-group-ref discovery-group-name="my-discovery-group"/> </cluster-connection> </cluster-connections>
In the above cluster connection all parameters have been explicitly specified. The following shows all the available configuration options
address
. Each cluster connection only applies to
messages sent to an address that starts with this value.
In this case, this cluster connection will load balance messages sent to
address that start with jms
. This cluster connection,
will, in effect apply to all JMS queue and topic subscriptions since they
map to core queues that start with the substring "jms".
The address can be any value and you can have many cluster connections
with different values of address
, simultaneously
balancing messages for those addresses, potentially to different clusters of
servers. By having multiple cluster connections on different addresses a
single HornetQ Server can effectively take part in multiple clusters
simultaneously.
Be careful not to have multiple cluster connections with overlapping
values of address
, e.g. "europe" and "europe.news" since
this could result in the same messages being distributed between more than
one cluster connection, possibly resulting in duplicate deliveries.
This parameter is mandatory.
max-retry-interval
. This is how many times a cluster connection should try
to reconnect if the connection fails, -1 means for ever.
retry-interval
. We mentioned before that, internally,
cluster connections cause bridges to be created between the nodes of the
cluster. If the cluster connection is created and the target node has not
been started, or say, is being rebooted, then the cluster connections from
other nodes will retry connecting to the target until it comes back up, in
the same way as a bridge does.
This parameter determines the interval in milliseconds between retry
attempts. It has the same meaning as the retry-interval
on a bridge (as described in Chapter 36, Core Bridges).
This parameter is optional and its default value is 500
milliseconds.
retry-interval-multiplier
. This is a multiplier used to increase the
retry-interval
after each reconnect attempt, default is 1.
use-duplicate-detection
. Internally cluster connections
use bridges to link the nodes, and bridges can be configured to add a
duplicate id property in each message that is forwarded. If the target node
of the bridge crashes and then recovers, messages might be resent from the
source node. By enabling duplicate detection any duplicate messages will be
filtered out and ignored on receipt at the target node.
This parameter has the same meaning as use-duplicate-detection
on a bridge. For more information on
duplicate detection, please see Chapter 37, Duplicate Message Detection.
This parameter is optional and has a default value of true
.
forward-when-no-consumers
. This parameter determines
whether messages will be distributed round robin between other nodes of the
cluster irrespective of whether there are matching or
indeed any consumers on other nodes.
If this is set to true
then each incoming message will
be round robin'd even though the same queues on the other nodes of the
cluster may have no consumers at all, or they may have consumers that have
non matching message filters (selectors). Note that HornetQ will
not forward messages to other nodes if there are no
queues of the same name on the other nodes, even if
this parameter is set to true
.
If this is set to false
then HornetQ will only forward
messages to other nodes of the cluster if the address to which they are
being forwarded has queues which have consumers, and if those consumers have
message filters (selectors) at least one of those selectors must match the
message.
This parameter is optional, the default value is false
.
min-large-message-size
. This parameters determines when a
message should be splitted with multiple packages when sent over the cluster.
This parameter is optional and its default is at 100K.
reconnect-attempts"
.The number of times the system will
try to connect a node on the cluster. If the max-retry is achieved this node will
be considered permanently down and the system will stop routing messages to this
node.
This parameter is optional and its default is at -1 (infinite retries).
max-hops
. When a cluster connection decides the set of
nodes to which it might load balance a message, those nodes do not have to
be directly connected to it via a cluster connection. HornetQ can be
configured to also load balance messages to nodes which might be connected
to it only indirectly with other HornetQ servers as intermediates in a
chain.
This allows HornetQ to be configured in more complex topologies and still provide message load balancing. We'll discuss this more later in this chapter.
The default value for this parameter is 1
, which means
messages are only load balanced to other HornetQ serves which are directly
connected to this server. This parameter is optional.
discovery-group-ref
. This parameter determines which
discovery group is used to obtain the list of other servers in the cluster
that this cluster connection will make connections to.
connection-ttl
. This is how long a cluster connection should stay alive if it
stops receiving messages from a specific node in the cluster
check-period
. The period (in milliseconds) used to check if the cluster connection
has failed to receive pings from another server
call-timeout
. When a packet is sent via a cluster connection and is a blocking
call, i.e. for acknowledgements, this is how long it will wait for the reply before throwing an exception
call-failover-timeout
. Similar to call-timeout
but used
when a call is made during a failover attempt
confirmation-window-size
. The size of the window used for sending confirmations
from the server connected to, default is -1 which is no window.
Alternatively if you would like your cluster connections to use a static list of servers for discovery then you can do it like this.
<cluster-connection name="my-cluster"> <address>jms</address> <connector-ref>netty-connector</connector-ref> <retry-interval>500</retry-interval> <use-duplicate-detection>true</use-duplicate-detection> <forward-when-no-consumers>true</forward-when-no-consumers> <max-hops>1</max-hops> <static-connectors> <connector-ref>server0-connector</connector-ref> <connector-ref>server1-connector</connector-ref> </static-connectors> </cluster-connection>
Here we have defined 2 servers that we know for sure will that at least one will be available. There may be many more servers in the cluster but these will; be discovered via one of these connectors once an initial connection has been made.
When creating connections between nodes of a cluster to form a cluster connection,
HornetQ uses a cluster user and cluster password which is defined in hornetq-configuration.xml
:
<cluster-user>HORNETQ.CLUSTER.ADMIN.USER</cluster-user> <cluster-password>CHANGE ME!!</cluster-password>
It is imperative that these values are changed from their default, or remote clients will be able to make connections to the server using the default values. If they are not changed from the default, HornetQ will detect this and pester you with a warning on every start-up.
With HornetQ client-side load balancing, subsequent sessions created using a single session factory can be connected to different nodes of the cluster. This allows sessions to spread smoothly across the nodes of a cluster and not be "clumped" on any particular node.
The load balancing policy to be used by the client factory is configurable. HornetQ provides four out-of-the-box load balancing policies, and you can also implement your own and use that.
The out-of-the-box policies are
Round Robin. With this policy the first node is chosen randomly then each subsequent node is chosen sequentially in the same order.
For example nodes might be chosen in the order B, C, D, A, B, C, D, A, B or D, A, B, C, D, A, B, C, D or C, D, A, B, C, D, A, B, C.
Use org.hornetq.api.core.client.loadbalance.RoundRobinConnectionLoadBalancingPolicy
as the <connection-load-balancing-policy-class-name>
.
Random. With this policy each node is chosen randomly.
Use org.hornetq.api.core.client.loadbalance.RandomConnectionLoadBalancingPolicy
as the <connection-load-balancing-policy-class-name>
.
Random Sticky. With this policy the first node is chosen randomly and then re-used for subsequent connections.
Use org.hornetq.api.core.client.loadbalance.RandomStickyConnectionLoadBalancingPolicy
as the <connection-load-balancing-policy-class-name>
.
First Element. With this policy the "first" (i.e. 0th) node is always returned.
Use org.hornetq.api.core.client.loadbalance.FirstElementConnectionLoadBalancingPolicy
as the <connection-load-balancing-policy-class-name>
.
You can also implement your own policy by implementing the interface org.hornetq.api.core.client.loadbalance.ConnectionLoadBalancingPolicy
Specifying which load balancing policy to use differs whether you are using JMS or the
core API. If you don't specify a policy then the default will be used which is org.hornetq.api.core.client.loadbalance.RoundRobinConnectionLoadBalancingPolicy
.
If you're using JMS, and you're using JNDI on the server to put your JMS connection
factories into JNDI, then you can specify the load balancing policy directly in the
hornetq-jms.xml
configuration file on the server as follows:
<connection-factory name="ConnectionFactory"> <discovery-group-ref discovery-group-name="my-discovery-group"/> <entries> <entry name="ConnectionFactory"/> </entries> <connection-load-balancing-policy-class-name> org.hornetq.api.core.client.loadbalance.RandomConnectionLoadBalancingPolicy </connection-load-balancing-policy-class-name> </connection-factory>
The above example would deploy a JMS connection factory that uses the random connection load balancing policy.
If you're using JMS but you're instantiating your connection factory directly on the
client side then you can set the load balancing policy using the setter on the
HornetQConnectionFactory
before using it:
ConnectionFactory jmsConnectionFactory = HornetQJMSClient.createConnectionFactory(...); jmsConnectionFactory.setLoadBalancingPolicyClassName("com.acme.MyLoadBalancingPolicy");
If you're using the core API, you can set the load balancing policy directly on the
ServerLocator
instance you are using:
ServerLocator locator = HornetQClient.createServerLocatorWithHA(server1, server2); locator.setLoadBalancingPolicyClassName("com.acme.MyLoadBalancingPolicy");
The set of servers over which the factory load balances can be determined in one of two ways:
Specifying servers explicitly
Using discovery.
Sometimes you want to explicitly define a cluster more explicitly, that is control which server connect to each other in the cluster. This is typically used to form non symmetrical clusters such as chain cluster or ring clusters. This can only be done using a static list of connectors and is configured as follows:
<cluster-connection name="my-cluster"> <address>jms</address> <connector-ref>netty-connector</connector-ref> <retry-interval>500</retry-interval> <use-duplicate-detection>true</use-duplicate-detection> <forward-when-no-consumers>true</forward-when-no-consumers> <max-hops>1</max-hops> <static-connectors allow-direct-connections-only="true"> <connector-ref>server1-connector</connector-ref> </static-connectors> </cluster-connection>
In this example we have set the attribute allow-direct-connections-only
which means that
the only server that this server can create a cluster connection to is server1-connector. This means you can
explicitly create any cluster topology you want.
Another important part of clustering is message redistribution. Earlier we learned how
server side message load balancing round robins messages across the cluster. If forward-when-no-consumers
is false, then messages won't be forwarded to
nodes which don't have matching consumers, this is great and ensures that messages don't
arrive on a queue which has no consumers to consume them, however there is a situation
it doesn't solve: What happens if the consumers on a queue close after the messages have
been sent to the node? If there are no consumers on the queue the message won't get
consumed and we have a starvation situation.
This is where message redistribution comes in. With message redistribution HornetQ can be configured to automatically redistribute messages from queues which have no consumers back to other nodes in the cluster which do have matching consumers.
Message redistribution can be configured to kick in immediately after the last consumer on a queue is closed, or to wait a configurable delay after the last consumer on a queue is closed before redistributing. By default message redistribution is disabled.
Message redistribution can be configured on a per address basis, by specifying the redistribution delay in the address settings, for more information on configuring address settings, please see Chapter 25, Queue Attributes.
Here's an address settings snippet from hornetq-configuration.xml
showing how message redistribution is enabled for a set of queues:
<address-settings> <address-setting match="jms.#"> <redistribution-delay>0</redistribution-delay> </address-setting> </address-settings>
The above address-settings
block would set a redistribution-delay
of 0
for any queue which is bound
to an address that starts with "jms.". All JMS queues and topic subscriptions are bound
to addresses that start with "jms.", so the above would enable instant (no delay)
redistribution for all JMS queues and topic subscriptions.
The attribute match
can be an exact match or it can be a string
that conforms to the HornetQ wildcard syntax (described in Chapter 13, Understanding the HornetQ Wildcard Syntax).
The element redistribution-delay
defines the delay in milliseconds
after the last consumer is closed on a queue before redistributing messages from that
queue to other nodes of the cluster which do have matching consumers. A delay of zero
means the messages will be immediately redistributed. A value of -1
signifies that messages will never be redistributed. The default value is -1
.
It often makes sense to introduce a delay before redistributing as it's a common case that a consumer closes but another one quickly is created on the same queue, in such a case you probably don't want to redistribute immediately since the new consumer will arrive shortly.
HornetQ clusters can be connected together in many different topologies, let's consider the two most common ones here
A symmetric cluster is probably the most common cluster topology, and you'll be familiar with if you've had experience of JBoss Application Server clustering.
With a symmetric cluster every node in the cluster is connected to every other node in the cluster. In other words every node in the cluster is no more than one hop away from every other node.
To form a symmetric cluster every node in the cluster defines a cluster connection
with the attribute max-hops
set to 1
.
Typically the cluster connection will use server discovery in order to know what
other servers in the cluster it should connect to, although it is possible to
explicitly define each target server too in the cluster connection if, for example,
UDP is not available on your network.
With a symmetric cluster each node knows about all the queues that exist on all the other nodes and what consumers they have. With this knowledge it can determine how to load balance and redistribute messages around the nodes.
Don't forget this warning when creating a symmetric cluster.
With a chain cluster, each node in the cluster is not connected to every node in the cluster directly, instead the nodes form a chain with a node on each end of the chain and all other nodes just connecting to the previous and next nodes in the chain.
An example of this would be a three node chain consisting of nodes A, B and C. Node A is hosted in one network and has many producer clients connected to it sending order messages. Due to corporate policy, the order consumer clients need to be hosted in a different network, and that network is only accessible via a third network. In this setup node B acts as a mediator with no producers or consumers on it. Any messages arriving on node A will be forwarded to node B, which will in turn forward them to node C where they can get consumed. Node A does not need to directly connect to C, but all the nodes can still act as a part of the cluster.
To set up a cluster in this way, node A would define a cluster connection that connects to node B, and node B would define a cluster connection that connects to node C. In this case we only want cluster connections in one direction since we're only moving messages from node A->B->C and never from C->B->A.
For this topology we would set max-hops
to 2
. With a value of 2
the knowledge of what queues and
consumers that exist on node C would be propagated from node C to node B to node A.
Node A would then know to distribute messages to node B when they arrive, even
though node B has no consumers itself, it would know that a further hop away is node
C which does have consumers.
We define high availability as the ability for the system to continue functioning after failure of one or more of the servers.
A part of high availability is failover which we define as the ability for client connections to migrate from one server to another in event of server failure so client applications can continue to operate.
HornetQ allows servers to be linked together as live - backup groups where each live server can have 1 or more backup servers. A backup server is owned by only one live server. Backup servers are not operational until failover occurs, however 1 chosen backup, which will be in passive mode, announces its status and waits to take over the live servers work
Before failover, only the live server is serving the HornetQ clients while the backup servers remain passive or awaiting to become a backup server. When a live server crashes or is brought down in the correct mode, the backup server currently in passive mode will become live and another backup server will become passive. If a live server restarts after a failover then it will have priority and be the next server to become live when the current live server goes down, if the current live server is configured to allow automatic failback then it will detect the live server coming back up and automatically stop.
HornetQ supports two different strategies for backing up a server shared store and replication.
Only persistent message data will survive failover. Any non persistent message data will not be available after failover.
Replication is supported since version 2.3.
When using replication, the live and the backup servers do not share the same data directories, all data synchronization is done through network traffic. Therefore all (persistent) data traffic received by the live server will be duplicated to the backup.
Notice that upon start-up the backup server will first need to synchronize all existing data from the live server, before becoming capable of replacing the live server should it fail. So unlike the shared store case, a replicating backup will not be a fully operational backup right after start, but only after it finishes synchronizing the data. The time it will take for this to happen will depend on the amount of data to be synchronized and the connection speed.
The replicating live and backup pair must be part of a cluster, meaning that even tho you may have a single live/backup it is still regarded as a cluster and must have a cluster connection configured in both the live and tha backup's for the same address. Also all servers must be on the same cluster, and have the same cluster user and password.
There are two ways that a backup server will locate a live server to replicate from, these are:
specifying a node group
. You can specify a group of live servers that a backup
server can connect to. This is done by configuring backup-group-name
in the main
hornetq-configuration.xml
. A Backup server will only connect to a live server that
shares the same node group name
connecting to any live
. Simply put not configuring backup-group-name
will allow a backup server to connect to any live server
The backup will search for any live server that it is configured to connect to. It then tries to replicate with each live server in turn until it finds a live server that has no current backup configured. If no live server is available it will wait until the cluster topology changes and repeats the process.
Much like in the shared-store case, when the live server stops or crashes, its replicating backup will become active and take over its duties. Specifically, the backup will become active when it loses connection to its live server. This can be problematic because this can also happen because of a temporary network problem. In order to address this issue, the backup will try to determine whether it still can connect to the other servers in the cluster. If it can connect to more than half the servers, it will become active, if more than half the servers also disappeared with the live, the backup will wait and try reconnecting with the live. This avoids a split brain situation.
To configure the live and backup servers to be a replicating pair, configure
both hornetq-configuration.xml
to have:
<shared-store>false</shared-store> . . . <cluster-connections> <cluster-connection name="my-cluster"> <cluster-user>fish<cluster-user> <cluster-password>ILikeToSwim<cluster-password> ... </cluster-connection> </cluster-connections>
The backup server must be flagged explicitly as a backup.
<backup>true</backup> <connectors> <connector name="nameOfConfiguredLiveServerConnector"> <factory-class> org.hornetq.core.remoting.impl.netty.NettyConnectorFactory </factory-class> <param key="port" value="5445"/> </connector> <!-- a real configuration could have more connectors here --> <connectors>
When using a shared store, both live and backup servers share the same entire data directory using a shared file system. This means the paging directory, journal directory, large messages and binding journal.
When failover occurs and a backup server takes over, it will load the persistent storage from the shared file system and clients can connect to it.
This style of high availability differs from data replication in that it requires a shared file system which is accessible by both the live and backup nodes. Typically this will be some kind of high performance Storage Area Network (SAN). We do not recommend you use Network Attached Storage (NAS), e.g. NFS mounts to store any shared journal (NFS is slow).
The advantage of shared-store high availability is that no replication occurs between the live and backup nodes, this means it does not suffer any performance penalties due to the overhead of replication during normal operation.
The disadvantage of shared store replication is that it requires a shared file system, and when the backup server activates it needs to load the journal from the shared store which can take some time depending on the amount of data in the store.
If you require the highest performance during normal operation, have access to a fast SAN, and can live with a slightly slower failover (depending on amount of data), we recommend shared store high availability
To configure the live and backup servers to share their store, configure
all hornetq-configuration.xml
:
<shared-store>true</shared-store>
Additionally, each backup server must be flagged explicitly as a backup:
<backup>true</backup>
In order for live - backup groups to operate properly with a shared store, both servers must have configured the location of journal directory to point to the same shared location (as explained in Section 15.3, “Configuring the message journal”)
todo write something about GFS
Also each node, live and backups, will need to have a cluster connection defined even if not part of a cluster. The Cluster Connection info defines how backup servers announce there presence to it's live server or any other nodes in the cluster. refer to Chapter 38, Clusters for details on how this is done.
After a live server has failed and a backup taken has taken over its duties, you may want to restart the live server and have clients fail back. To do this simply restart the original live server and kill the new live server. You can do this by killing the process itself or just waiting for the server to crash naturally
It is also possible to cause failover to occur on normal server shutdown, to enable
this set the following property to true in the hornetq-configuration.xml
configuration file like so:
<failover-on-shutdown>true</failover-on-shutdown>
By default this is set to false, if by some chance you have set this to false but still want to stop the server normally and cause failover then you can do this by using the management API as explained at Section 30.1.1.1, “Core Server Management”
You can also force the new live server to shutdown when the old live server comes back up allowing
the original live server to take over automatically by setting the following property in the
hornetq-configuration.xml
configuration file as follows:
<allow-failback>true</allow-failback>
In replication HA mode you need to set an extra property check-for-live-server
to true
in order to force the new live server to shutdown when the old live server
comes back up in hornetq-configuration.xml
configuration file as follows:
<check-for-live-server>true</check-for-live-server>
HornetQ defines two types of client failover:
Automatic client failover
Application-level client failover
HornetQ also provides 100% transparent automatic reattachment of connections to the same server (e.g. in case of transient network problems). This is similar to failover, except it's reconnecting to the same server and is discussed in Chapter 34, Client Reconnection and Session Reattachment
During failover, if the client has consumers on any non persistent or temporary queues, those queues will be automatically recreated during failover on the backup node, since the backup node will not have any knowledge of non persistent queues.
HornetQ clients can be configured to receive knowledge of all live and backup servers, so that in event of connection failure at the client - live server connection, the client will detect this and reconnect to the backup server. The backup server will then automatically recreate any sessions and consumers that existed on each connection before failover, thus saving the user from having to hand-code manual reconnection logic.
HornetQ clients detect connection failure when it has not received packets from
the server within the time given by client-failure-check-period
as explained in section Chapter 17, Detecting Dead Connections. If the client does not
receive data in good time, it will assume the connection has failed and attempt
failover. Also if the socket is closed by the OS, usually if the server process is
killed rather than the machine itself crashing, then the client will failover straight away.
HornetQ clients can be configured to discover the list of live-backup server groups in a number of different ways. They can be configured explicitly or probably the most common way of doing this is to use server discovery for the client to automatically discover the list. For full details on how to configure server discovery, please see Chapter 38, Clusters. Alternatively, the clients can explicitly connect to a specific server and download the current servers and backups see Chapter 38, Clusters.
To enable automatic client failover, the client must be configured to allow non-zero reconnection attempts (as explained in Chapter 34, Client Reconnection and Session Reattachment).
By default failover will only occur after at least one connection has been made to the live server. In other words, by default, failover will not occur if the client fails to make an initial connection to the live server - in this case it will simply retry connecting to the live server according to the reconnect-attempts property and fail after this number of attempts.
Since the client doesn't learn about the full topology until after the first
connection is made there is a window where it doesn't know about the backup. If a failure happens at
this point the client can only try reconnecting to the original live server. To configure
how many attempts the client will make you can set the property initialConnectAttempts
on the ClientSessionFactoryImpl
or HornetQConnectionFactory
or
initial-connect-attempts
in xml. The default for this is 0
, that
is try only once. Once the number of attempts has been made an exception will be thrown.
For examples of automatic failover with transacted and non-transacted JMS sessions, please see Section 11.1.67, “Transaction Failover” and Section 11.1.41, “Non-Transaction Failover With Server Data Replication”.
HornetQ does not replicate full server state between live and backup servers. When the new session is automatically recreated on the backup it won't have any knowledge of messages already sent or acknowledged in that session. Any in-flight sends or acknowledgements at the time of failover might also be lost.
By replicating full server state, theoretically we could provide a 100% transparent seamless failover, which would avoid any lost messages or acknowledgements, however this comes at a great cost: replicating the full server state (including the queues, session, etc.). This would require replication of the entire server state machine; every operation on the live server would have to replicated on the replica server(s) in the exact same global order to ensure a consistent replica state. This is extremely hard to do in a performant and scalable way, especially when one considers that multiple threads are changing the live server state concurrently.
It is possible to provide full state machine replication using techniques such as virtual synchrony, but this does not scale well and effectively serializes all operations to a single thread, dramatically reducing concurrency.
Other techniques for multi-threaded active replication exist such as replicating lock states or replicating thread scheduling but this is very hard to achieve at a Java level.
Consequently it has decided it was not worth massively reducing performance and concurrency for the sake of 100% transparent failover. Even without 100% transparent failover, it is simple to guarantee once and only once delivery, even in the case of failure, by using a combination of duplicate detection and retrying of transactions. However this is not 100% transparent to the client code.
If the client code is in a blocking call to the server, waiting for a response to continue its execution, when failover occurs, the new session will not have any knowledge of the call that was in progress. This call might otherwise hang for ever, waiting for a response that will never come.
To prevent this, HornetQ will unblock any blocking calls that were in progress
at the time of failover by making them throw a javax.jms.JMSException
(if using JMS), or a HornetQException
with error code HornetQException.UNBLOCKED
. It is up to the client code to catch
this exception and retry any operations if desired.
If the method being unblocked is a call to commit(), or prepare(), then the
transaction will be automatically rolled back and HornetQ will throw a javax.jms.TransactionRolledBackException
(if using JMS), or a
HornetQException
with error code HornetQException.TRANSACTION_ROLLED_BACK
if using the core
API.
If the session is transactional and messages have already been sent or acknowledged in the current transaction, then the server cannot be sure that messages sent or acknowledgements have not been lost during the failover.
Consequently the transaction will be marked as rollback-only, and any
subsequent attempt to commit it will throw a javax.jms.TransactionRolledBackException
(if using JMS), or a
HornetQException
with error code HornetQException.TRANSACTION_ROLLED_BACK
if using the core
API.
The caveat to this rule is when XA is used either via JMS or through the core API.
If 2 phase commit is used and prepare has already been called then rolling back could
cause a HeuristicMixedException
. Because of this the commit will throw
a XAException.XA_RETRY
exception. This informs the Transaction Manager
that it should retry the commit at some later point in time, a side effect of this is
that any non persistent messages will be lost. To avoid this use persistent
messages when using XA. With acknowledgements this is not an issue since they are
flushed to the server before prepare gets called.
It is up to the user to catch the exception, and perform any client side local rollback code as necessary. There is no need to manually rollback the session - it is already rolled back. The user can then just retry the transactional operations again on the same session.
HornetQ ships with a fully functioning example demonstrating how to do this, please see Section 11.1.67, “Transaction Failover”
If failover occurs when a commit call is being executed, the server, as previously described, will unblock the call to prevent a hang, since no response will come back. In this case it is not easy for the client to determine whether the transaction commit was actually processed on the live server before failure occurred.
If XA is being used either via JMS or through the core API then an XAException.XA_RETRY
is thrown. This is to inform Transaction Managers that a retry should occur at some point. At
some later point in time the Transaction Manager will retry the commit. If the original
commit hadn't occurred then it will still exist and be committed, if it doesn't exist
then it is assumed to have been committed although the transaction manager may log a warning.
To remedy this, the client can simply enable duplicate detection (Chapter 37, Duplicate Message Detection) in the transaction, and retry the transaction operations again after the call is unblocked. If the transaction had indeed been committed on the live server successfully before failover, then when the transaction is retried, duplicate detection will ensure that any durable messages resent in the transaction will be ignored on the server to prevent them getting sent more than once.
By catching the rollback exceptions and retrying, catching unblocked calls and enabling duplicate detection, once and only once delivery guarantees for messages can be provided in the case of failure, guaranteeing 100% no loss or duplication of messages.
If the session is non transactional, messages or acknowledgements can be lost in the event of failover.
If you wish to provide once and only once delivery guarantees for non transacted sessions too, enabled duplicate detection, and catch unblock exceptions as described in Section 39.2.1.3, “Handling Blocking Calls During Failover”
JMS provides a standard mechanism for getting notified asynchronously of
connection failure: java.jms.ExceptionListener
. Please consult
the JMS javadoc or any good JMS tutorial for more information on how to use
this.
The HornetQ core API also provides a similar feature in the form of the class
org.hornet.core.client.SessionFailureListener
Any ExceptionListener or SessionFailureListener instance will always be called by
HornetQ on event of connection failure, irrespective of whether the connection was successfully failed over,
reconnected or reattached, however you can find out if reconnect or reattach has happened
by either the failedOver
flag passed in on the connectionFailed
on SessionfailureListener
or by inspecting the error code on the
javax.jms.JMSException
which will be one of the following:
Table 39.1. JMSException error codes
error code | Description |
---|---|
FAILOVER | Failover has occurred and we have successfully reattached or reconnected. |
DISCONNECT | No failover has occurred and we are disconnected. |
In some cases you may not want automatic client failover, and prefer to handle any connection failure yourself, and code your own manually reconnection logic in your own failure handler. We define this as application-level failover, since the failover is handled at the user application level.
To implement application-level failover, if you're using JMS then you need to set
an ExceptionListener
class on the JMS connection. The ExceptionListener
will be called by HornetQ in the event that
connection failure is detected. In your ExceptionListener
, you
would close your old JMS connections, potentially look up new connection factory
instances from JNDI and creating new connections. In this case you may well be using
HA-JNDI
to ensure that the new connection factory is looked up from a different
server.
For a working example of application-level failover, please see Section 11.1.2, “Application-Layer Failover”.
If you are using the core API, then the procedure is very similar: you would set a
FailureListener
on the core ClientSession
instances.
HornetQ distributes a native library, used as a bridge between HornetQ and linux libaio.
libaio
is a library, developed as part of the linux kernel project.
With libaio
we submit writes to the operating system where they are
processed asynchronously. Some time later the OS will call our code back when they have been
processed.
We use this in our high performance journal if configured to do so, please see Chapter 15, Persistence.
These are the native libraries distributed by HornetQ:
libHornetQAIO32.so - x86 32 bits
libHornetQAIO64.so - x86 64 bits
When using libaio, HornetQ will always try loading these files as long as they are on the library path.
In the case that you are using Linux on a platform other than x86_32 or x86_64 (for example Itanium 64 bits or IBM Power) you may need to compile the native library, since we do not distribute binaries for those platforms with the release.
At the moment the native layer is only available on Linux. If you are in a platform other than Linux the native compilation will not work
The native library uses autoconf what makes the compilation process easy, however you need to install extra packages as a requirement for compilation:
gcc - C Compiler
gcc-c++ or g++ - Extension to gcc with support for C++
autoconf - Tool for automating native build process
make - Plain old make
automake - Tool for automating make generation
libtool - Tool for link editing native libraries
libaio - library to disk asynchronous IO kernel functions
libaio-dev - Compilation support for libaio
A full JDK installed with the environment variable JAVA_HOME set to its location
To perform this installation on RHEL or Fedora, you can simply type this at a command line:
sudo yum install automake libtool autoconf gcc-c++ gcc libaio libaio-devel make
Or on debian systems:
sudo apt-get install automake libtool autoconf gcc-g++ gcc libaio libaio-dev make
You could find a slight variation of the package names depending on the version and linux distribution. (for example gcc-c++ on Fedora versus g++ on Debian systems)
In the distribution, in the native-src
directory, execute the
shell script bootstrap
. This script will invoke automake
and make
what will create all the make
files and the native library.
someUser@someBox:/messaging-distribution/native-src$ ./bootstrap checking for a BSD-compatible install... /usr/bin/install -c checking whether build environment is sane... yes checking for a thread-safe mkdir -p... /bin/mkdir -p ... configure: creating ./config.status config.status: creating Makefile config.status: creating ./src/Makefile config.status: creating config.h config.status: config.h is unchanged config.status: executing depfiles commands config.status: executing libtool commands ...
The produced library will be at ./native-src/src/.libs/libHornetQAIO.so
. Simply move that file over
bin
on the distribution or the place you have chosen on the
library path.
If you want to perform changes on the HornetQ libaio code, you could just call
make directly at the native-src
directory.
This chapter describes how HornetQ uses and pools threads and how you can manage them.
First we'll discuss how threads are managed and used on the server side, then we'll look at the client side.
Each HornetQ Server maintains a single thread pool for general use, and a scheduled thread pool for scheduled use. A Java scheduled thread pool cannot be configured to use a standard thread pool, otherwise we could use a single thread pool for both scheduled and non scheduled activity.
When using old (blocking) IO, a separate thread pool is also used to service connections. Since old IO requires a thread per connection it does not make sense to get them from the standard pool as the pool will easily get exhausted if too many connections are made, resulting in the server "hanging" since it has no remaining threads to do anything else. If you require the server to handle many concurrent connections you should make sure you use NIO, not old IO.
When using new IO (NIO), HornetQ will, by default, use a number of threads equal to
three times the number of cores (or hyper-threads) as reported by
Runtime.getRuntime().availableProcessors() for processing incoming packets. If you want
to override this value, you can set the number of threads by specifying the parameter
nio-remoting-threads
in the transport configuration. See the
Chapter 16, Configuring the Transport for more information on this.
There are also a small number of other places where threads are used directly, we'll discuss each in turn.
The server scheduled thread pool is used for most activities on the server side
that require running periodically or with delays. It maps internally to a java.util.concurrent.ScheduledThreadPoolExecutor
instance.
The maximum number of thread used by this pool is configure in hornetq-configuration.xml
with the scheduled-thread-pool-max-size
parameter. The default value is
5
threads. A small number of threads is usually sufficient
for this pool.
This general purpose thread pool is used for most asynchronous actions on the
server side. It maps internally to a java.util.concurrent.ThreadPoolExecutor
instance.
The maximum number of thread used by this pool is configure in hornetq-configuration.xml
with the thread-pool-max-size
parameter.
If a value of -1
is used this signifies that the thread pool
has no upper bound and new threads will be created on demand if there are not enough
threads available to satisfy a request. If activity later subsides then threads are
timed-out and closed.
If a value of n
where n
is a positive integer
greater than zero is used this signifies that the thread pool is bounded. If more
requests come in and there are no free threads in the pool and the pool is full then
requests will block until a thread becomes available. It is recommended that a
bounded thread pool is used with caution since it can lead to dead-lock situations
if the upper bound is chosen to be too low.
The default value for thread-pool-max-size
is 30
.
See the J2SE javadoc for more information on unbounded (cached), and bounded (fixed) thread pools.
A single thread is also used on the server side to scan for expired messages in queues. We cannot use either of the thread pools for this since this thread needs to run at its own configurable priority.
For more information on configuring the reaper, please see Chapter 22, Message Expiry.
Asynchronous IO has a thread pool for receiving and dispatching events out of the native layer. You will find it on a thread dump with the prefix HornetQ-AIO-poller-pool. HornetQ uses one thread per opened file on the journal (there is usually one).
There is also a single thread used to invoke writes on libaio. We do that to avoid context switching on libaio that would cause performance issues. You will find this thread on a thread dump with the prefix HornetQ-AIO-writer-pool.
On the client side, HornetQ maintains a single static scheduled thread pool and a single static general thread pool for use by all clients using the same classloader in that JVM instance.
The static scheduled thread pool has a maximum size of 5
threads,
and the general purpose thread pool has an unbounded maximum size.
If required HornetQ can also be configured so that each ClientSessionFactory
instance does not use these static pools but instead
maintains its own scheduled and general purpose pool. Any sessions created from that
ClientSessionFactory
will use those pools instead.
To configure a ClientSessionFactory
instance to use its own pools,
simply use the appropriate setter methods immediately after creation, for
example:
ServerLocator locator = HornetQClient.createServerLocatorWithoutHA(...) ClientSessionFactory myFactory = locator.createClientSessionFactory(); myFactory.setUseGlobalPools(false); myFactory.setScheduledThreadPoolMaxSize(10); myFactory.setThreadPoolMaxSize(-1);
If you're using the JMS API, you can set the same parameters on the
ClientSessionFactory and use it to create the ConnectionFactory
instance, for example:
ConnectionFactory myConnectionFactory = HornetQJMSClient.createConnectionFactory(myFactory);
If you're using JNDI to instantiate HornetQConnectionFactory
instances, you can also set these parameters in the hornetq-jms.xml
file where you describe your connection factory, for example:
<connection-factory name="ConnectionFactory"> <connectors> <connector-ref connector-name="netty"/> </connectors> <entries> <entry name="ConnectionFactory"/> <entry name="XAConnectionFactory"/> </entries> <use-global-pools>false</use-global-pools> <scheduled-thread-pool-max-size>10</scheduled-thread-pool-max-size> <thread-pool-max-size>-1</thread-pool-max-size> </connection-factory>
HornetQ uses the JBoss Logging framework to do its logging and is configurable via the logging.properties
file found in the configuration directories. This is configured by Default to log to both the console and to a file.
There are 6 loggers availabe which are as follows:
Table 42.1. Global Configuration Properties
Logger | Logger Description |
---|---|
org.jboss.logging | Logs any calls not handled by the HornetQ loggers |
org.hornetq.core.server | Logs the core server |
org.hornetq.utils | Logs utility calls |
org.hornetq.journal | Logs Journal calls |
org.hornetq.jms | Logs JMS calls |
org.hornetq.integration.bootstrap | Logs bootstrap calls |
you can configure the levels on these loggers independently in the appropriate logging.properties
file
Firstly, if you want to enable logging on the client side you need to include the jboss logging jars in your library. If you are using the distribution make sure the jnp-client.jar is included or if you are using maven add the following dependencies.
<dependency> <groupId>org.jboss.naming</groupId> <artifactId>jnp-client</artifactId> <version>5.0.5.Final</version> <exclusions> <exclusion> <groupId>org.jboss.logging</groupId> <artifactId>jboss-logging-spi</artifactId> </exclusion> </exclusions> </dependency> <dependency> <groupId>org.jboss.logmanager</groupId> <artifactId>jboss-logmanager</artifactId> <version>1.3.1.Final</version> </dependency> <dependency> <groupId>org.hornetq</groupId> <artifactId>hornetq-core-client</artifactId> <version>2.3.0.Final</version> </dependency>
The first dependency jnp-client
is not actually needed for logging, however this is needed for
using JNDI and imports a previous version JBoss logging which needs to be excluded
There are 2 properties you need to set when starting your java program, the first is to set the Log Manager to use
the JBoss Log Manager, this is done by setting the -Djava.util.logging.manager
property i.e.
-Djava.util.logging.manager=org.jboss.logmanager.LogManager
The second is to set the location of the logging.properties file to use, this is done via the -Dlogging.configuration
for instance -Dlogging.configuration=file:///home/user/projects/myProject/logging.properties
.
The following is a typical logging.properties for a client
# Root logger option loggers=org.jboss.logging,org.hornetq.core.server,org.hornetq.utils,org.hornetq.journal,org.hornetq.jms,org.hornetq.ra # Root logger level logger.level=INFO # HornetQ logger levels logger.org.hornetq.core.server.level=INFO logger.org.hornetq.utils.level=INFO logger.org.hornetq.jms.level=DEBUG # Root logger handlers logger.handlers=FILE,CONSOLE # Console handler configuration handler.CONSOLE=org.jboss.logmanager.handlers.ConsoleHandler handler.CONSOLE.properties=autoFlush handler.CONSOLE.level=FINE handler.CONSOLE.autoFlush=true handler.CONSOLE.formatter=PATTERN # File handler configuration handler.FILE=org.jboss.logmanager.handlers.FileHandler handler.FILE.level=FINE handler.FILE.properties=autoFlush,fileName handler.FILE.autoFlush=true handler.FILE.fileName=hornetq.log handler.FILE.formatter=PATTERN # Formatter pattern configuration formatter.PATTERN=org.jboss.logmanager.formatters.PatternFormatter formatter.PATTERN.properties=pattern formatter.PATTERN.pattern=%d{HH:mm:ss,SSS} %-5p [%c] %s%E%n
The HornetQ REST interface allows you to leverage the reliability and scalability features of HornetQ over a simple REST/HTTP interface. Messages are produced and consumed by sending and receiving simple HTTP messages that contain the content you want to push around. For instance, here's a simple example of posting an order to an order processing queue express as an HTTP message:
POST /queue/orders/create HTTP/1.1 Host: example.com Content-Type: application/xml <order> <name>Bill</name> <item>iPhone 4</item> <cost>$199.99</cost> </order>
As you can see, we're just posting some arbitrary XML document to a URL. When the XML is received on the server is it processed within HornetQ as a JMS message and distributed through core HornetQ. Simple and easy. Consuming messages from a queue or topic looks very similar. We'll discuss the entire interface in detail later in this docbook.
Why would you want to use HornetQ's REST interface? What are the goals of the REST interface?
Easily usable by machine-based (code) clients.
Zero client footprint. We want HornetQ to be usable by any client/programming language that has an adequate HTTP client library. You shouldn't have to download, install, and configure a special library to interact with HornetQ.
Lightweight interoperability. The HTTP protocol is strong enough to be our message exchange protocol. Since interactions are RESTful the HTTP uniform interface provides all the interoperability you need to communicate between different languages, platforms, and even messaging implementations that choose to implement the same RESTful interface as HornetQ (i.e. the REST-* effort.)
No envelope (e.g. SOAP) or feed (e.g. Atom) format requirements. You shouldn't have to learn, use, or parse a specific XML document format in order to send and receive messages through HornetQ's REST interface.
Leverage the reliability, scalability, and clustering features of HornetQ on the back end without sacrificing the simplicity of a REST interface.
HornetQ's REST interface is installed as a Web archive (WAR). It depends on the RESTEasy project and can currently only run within a servlet container. Installing the HornetQ REST interface is a little bit different depending whether HornetQ is already installed and configured for your environment (e.g. you're deploying within JBoss AS 7) or you want the HornetQ REST WAR to startup and manage the HornetQ server (e.g. you're deploying within something like Apache Tomcat).
The section should be used when you want to use the HornetQ REST interface in an environment that already has HornetQ installed and running, e.g. JBoss AS 7. You must create a Web archive (.WAR) file with the following web.xml settings:
<web-app> <listener> <listener-class> org.jboss.resteasy.plugins.server.servlet.ResteasyBootstrap </listener-class> </listener> <listener> <listener-class> org.hornetq.rest.integration.RestMessagingBootstrapListener </listener-class> </listener> <filter> <filter-name>Rest-Messaging</filter-name> <filter-class> org.jboss.resteasy.plugins.server.servlet.FilterDispatcher </filter-class> </filter> <filter-mapping> <filter-name>Rest-Messaging</filter-name> <url-pattern>/*</url-pattern> </filter-mapping> </web-app>
Within your WEB-INF/lib directory you must have the hornetq-rest.jar file. If RESTEasy is not installed within your environment, you must add the RESTEasy jar files within the lib directory as well. Here's a sample Maven pom.xml that can build your WAR for this case.
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>org.somebody</groupId> <artifactId>myapp</artifactId> <packaging>war</packaging> <name>My App</name> <version>0.1-SNAPSHOT</version> <repositories> <repository> <id>jboss</id> <url>http://repository.jboss.org/nexus/content/groups/public/</url> </repository> </repositories> <build> <plugins> <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-compiler-plugin</artifactId> <configuration> <source>1.6</source> <target>1.6</target> </configuration> </plugin> </plugins> </build> <dependencies> <dependency> <groupId>org.hornetq.rest</groupId> <artifactId>hornetq-rest</artifactId> <version>2.3.0-SNAPSHOT</version> </dependency> </dependencies> </project>
JBoss AS 7 loads classes differently than previous versions. To work properly in AS 7 the WAR will need this in its MANIFEST.MF:
Dependencies: org.hornetq, org.jboss.netty
You can add this to the<plugins>
section of the pom.xml to create this entry automatically:
<plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-war-plugin</artifactId> <configuration> <archive> <manifestEntries> <Dependencies>org.hornetq, org.jboss.netty</Dependencies> </manifestEntries> </archive> </configuration> </plugin>
You can bootstrap HornetQ within your WAR as well. To do this, you must have the HornetQ core and JMS jars along with Netty, Resteasy, and the HornetQ REST jar within your WEB-INF/lib. You must also have a hornetq-configuration.xml, hornetq-jms.xml, and hornetq-users.xml config files within WEB-INF/classes. The examples that come with the HornetQ REST distribution show how to do this. You must also add an additional listener to your web.xml file. Here's an example:
<web-app> <listener> <listener-class> org.jboss.resteasy.plugins.server.servlet.ResteasyBootstrap </listener-class> </listener> <listener> <listener-class> org.hornetq.rest.integration.HornetqBootstrapListener </listener-class> </listener> <listener> <listener-class> org.hornetq.rest.integration.RestMessagingBootstrapListener </listener-class> </listener> <filter> <filter-name>Rest-Messaging</filter-name> <filter-class> org.jboss.resteasy.plugins.server.servlet.FilterDispatcher </filter-class> </filter> <filter-mapping> <filter-name>Rest-Messaging</filter-name> <url-pattern>/*</url-pattern> </filter-mapping> </web-app>
Here's a Maven pom.xml file for creating a WAR for this environment. Make sure your hornetq configuration files are within the src/main/resources directory so that they are stuffed within the WAR's WEB-INF/classes directory!
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>org.somebody</groupId> <artifactId>myapp</artifactId> <packaging>war</packaging> <name>My App</name> <version>0.1-SNAPSHOT</version> <repositories> <repository> <id>jboss</id> <url>http://repository.jboss.org/nexus/content/groups/public/</url> </repository> </repositories> <build> <plugins> <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-compiler-plugin</artifactId> <configuration> <source>1.6</source> <target>1.6</target> </configuration> </plugin> </plugins> </build> <dependencies> <dependency> <groupId>org.hornetq</groupId> <artifactId>hornetq-core</artifactId> <version>2.3.0-SNAPSHOT</version> </dependency> <dependency> <groupId>io.netty</groupId> <artifactId>netty</artifactId> <version>3.4.5.Final</version> </dependency> <dependency> <groupId>org.hornetq</groupId> <artifactId>hornetq-jms</artifactId> <version>2.3.0-SNAPSHOT</version> </dependency> <dependency> <groupId>org.jboss.spec.javax.jms</groupId> <artifactId>jboss-jms-api_1.1_spec</artifactId> <version>1.0.0.Final</version> </dependency> <dependency> <groupId>org.hornetq.rest</groupId> <artifactId>hornetq-rest</artifactId> <version>2.3.0-SNAPSHOT</version> </dependency> <dependency> <groupId>org.jboss.resteasy</groupId> <artifactId>resteasy-jaxrs</artifactId> <version>2.3.4.Final</version> </dependency> <dependency> <groupId>org.jboss.resteasy</groupId> <artifactId>resteasy-jaxb-provider</artifactId> <version>2.3.4.Final</version> </dependency> </dependencies> </project>
The HornetQ REST implementation does have some configuration
options. These are configured via XML configuration file that must be in
your WEB-INF/classes directory. You must set the web.xml context-param
rest.messaging.config.file
to specify the name of the
configuration file. Below is the format of the XML configuration file
and the default values for each.
<rest-messaging> <server-in-vm-id>0</server-in-vm-id> <use-link-headers>false</use-link-headers> <default-durable-send>false</default-durable-send> <dups-ok>true</dups-ok> <topic-push-store-dir>topic-push-store</topic-push-store-dir> <queue-push-store-dir>queue-push-store</queue-push-store-dir> <producer-time-to-live>0</producer-time-to-live> <producer-session-pool-size>10</producer-session-pool-size> <session-timeout-task-interval>1</session-timeout-task-interval> <consumer-session-timeout-seconds>300</consumer-session-timeout-seconds> <consumer-window-size>-1</consumer-window-size> </rest-messaging>
Let's give an explanation of each config option.
server-in-vm-id
. The HornetQ REST
impl uses the IN-VM transport to communicate with HornetQ.
It uses the default server id, which is "0".
use-link-headers
. By default, all
links (URLs) are published using custom headers. You can
instead have the HornetQ REST implementation publish links
using the
Link Header specification
instead if you desire.
default-durable-send
. Whether a posted
message should be persisted by default if the user does not
specify a durable query parameter.
dups-ok
. If this is true, no duplicate
detection protocol will be enforced for message posting.
topic-push-store-dir
. This must be
a relative or absolute file system path. This is a directory
where push registrations for topics are stored. See
Pushing Messages.
queue-push-store-dir
. This must be
a relative or absolute file system path. This is a
directory where push registrations for queues are stored.
See Pushing Messages.
producer-session-pool-size
. The REST
implementation pools HornetQ sessions for sending messages.
This is the size of the pool. That number of sessions will
be created at startup time.
producer-time-to-live
. Default time
to live for posted messages. Default is no ttl.
session-timeout-task-interval
. Pull
consumers and pull subscriptions can time out. This is
the interval the thread that checks for timed-out sessions
will run at. A value of 1 means it will run every 1 second.
consumer-session-timeout-seconds
.
Timeout in seconds for pull consumers/subscriptions that
remain idle for that amount of time.
consumer-window-size
. For consumers,
this config option is the same as the HornetQ one of the
same name. It will be used by sessions created by the
HornetQ REST implementation.
The HornetQ REST interface publishes a variety of REST resources to perform various tasks on a queue or topic. Only the top-level queue and topic URI schemes are published to the outside world. You must discover all over resources to interact with by looking for and traversing links. You'll find published links within custom response headers and embedded in published XML representations. Let's look at how this works.
To interact with a queue or topic you do a HEAD or GET request on the following relative URI pattern:
/queues/{name} /topics/{name}
The base of the URI is the base URL of the WAR you deployed the
HornetQ REST server within as defined in the Installation and
Configuration section of this document. Replace the
{name}
string within the above URI pattern with the
name of the queue or topic you are interested in interacting with. For
example if you have configured a JMS topic named "foo" within your
hornetq-jms.xml
file, the URI name should be
"jms.topic.foo". If you have configured a JMS queue name "bar" within
your hornetq-jms.xml
file, the URI name should be
"jms.queue.bar". Internally, HornetQ prepends the "jms.topic" or
"jms.queue" strings to the name of the deployed destination. Next,
perform your HEAD or GET request on this URI. Here's what a
request/response would look like.
HEAD /queues/jms.queue.bar HTTP/1.1 Host: example.com --- Response --- HTTP/1.1 200 Ok msg-create: http://example.com/queues/jms.queue.bar/create msg-pull-consumers: http://example.com/queues/jms.queue.bar/pull-consumers msg-push-consumers: http://example.com/queues/jms.queue.bar/push-consumers
The HEAD or GET response contains a number of custom response headers that are URLs to additional REST resources that allow you to interact with the queue or topic in different ways. It is important not to rely on the scheme of the URLs returned within these headers as they are an implementation detail. Treat them as opaque and query for them each and every time you initially interact (at boot time) with the server. If you treat all URLs as opaque then you will be isolated from implementation changes as the HornetQ REST interface evolves over time.
Below is a list of response headers you should expect when interacting with a Queue resource.
msg-create
. This is a URL you POST messages
to. The semantics of this link are described in
Posting Messages.
msg-create-with-id
. This is a URL template
you POST message to. The semantics of this link are described
in Posting Messages.
msg-pull-consumers
. This is a URL for
creating consumers that will pull from a queue. The semantics
of this link are described in HornetQ
REST Interface Basics.
msg-push-consumers
. This is a URL for
registering other URLs you want the HornetQ REST server to
push messages to. The semantics of this link are described
in Pushing Messages.
Below is a list of response headers you should expect when interacting with a Topic resource.
msg-create
. This is a URL you POST
messages to. The semantics of this link are described in
Posting Messages.
msg-create-with-id
. This is a URL
template you POST messages to. The semantics of this link
are described in Posting
Messages.
msg-pull-subscriptions
. This is a
URL for creating subscribers that will pull from a topic.
The semantics of this link are described in
Consuming Messages via Pull.
msg-push-subscriptions
. This is a
URL for registering other URLs you want the HornetQ REST
server to push messages to. The semantics of this link
are described in Pushing
Messages.
This chapter discusses the protocol for posting messages to a queue
or a topic. In HornetQ REST Interface Basics, you saw that a queue or topic resource publishes
variable custom headers that are links to other RESTful resources. The
msg-create
header is the URL you post messages to.
Messages are published to a queue or topic by sending a simple HTTP
message to the URL published by the msg-create header. The HTTP message
contains whatever content you want to publish to the HornetQ destination.
Here's an example scenario:
Obtain the starting msg-create
header from
the queue or topic resource.
HEAD /queues/jms.queue.bar HTTP/1.1 Host: example.com --- Response --- HTTP/1.1 200 Ok msg-create: http://example.com/queues/jms.queue.bar/create msg-create-with-id: http://example.com/queues/jms.queue.bar/create/{id}
Do a POST to the URL contained in the msg-create
header.
POST /queues/jms.queue.bar/create Host: example.com Content-Type: application/xml <order> <name>Bill</name> <item>iPhone4</name> <cost>$199.99</cost> </order> --- Response --- HTTP/1.1 201 Created msg-create-next: http://example.com/queues/jms.queue.bar/create/002
A successful response will return a 201 response code. Also
notice that a msg-create-next
response header
is sent as well. You must use this URL to POST your next message.
POST your next message to the queue using the URL returned in
the
msg-create-next
header.
POST /queues/jms.queue.bar/create/002 Host: example.com Content-Type: application/xml <order> <name>Monica</name> <item>iPad</item> <cost>$499.99</cost> </order> --- Response -- HTTP/1.1 201 Created msg-create-next: http://example.com/queues/jms.queue.bar/create/003
Continue using the new msg-create-next
header returned with each response.
It is VERY IMPORTANT that you never re-use returned
msg-create-next
headers to post new messages. This URL may
be uniquely generated for each message and used for duplicate detection. If
you lose the URL within the msg-create-next
header, then
just go back to the queue or topic resource to get the msg-create URL.
Sometimes you might have network problems when posting new
messages to a queue or topic. You may do a POST and never receive a
response. Unfortunately, you don't know whether or not the server
received the message and so a re-post of the message might cause
duplicates to be posted to the queue or topic. By default, the HornetQ
REST interface is configured to accept and post duplicate messages. You
can change this by turning on duplicate message detection by setting the
dups-ok
config option to false
as described in HornetQ REST Interface Basics. When you do this, the initial POST to the
msg-create URL will redirect you, using the standard HTTP 307
redirection mechanism to a unique URL to POST to. All other interactions
remain the same as discussed earlier. Here's an example:
Obtain the starting msg-create
header from
the queue or topic resource.
HEAD /queues/jms.queue.bar HTTP/1.1 Host: example.com --- Response --- HTTP/1.1 200 Ok msg-create: http://example.com/queues/jms.queue.bar/create msg-create-with-id: http://example.com/queues/jms.queue.bar/create/{id}
Do a POST to the URL contained in the msg-create
header.
POST /queues/jms.queue.bar/create Host: example.com Content-Type: application/xml <order> <name>Bill</name> <item>iPhone4</name> <cost>$199.99</cost> </order> --- Response --- HTTP/1.1 307 Redirect Location: http://example.com/queues/jms.queue.bar/create/001
A successful response will return a 307 response code. This
is standard HTTP protocol. It is telling you that you must re-POST
to the URL contained within the Location
header.
re-POST your message to the URL provided within the
Location
header.
POST /queues/jms.queue.bar/create/001 Host: example.com Content-Type: application/xml <order> <name>Bill</name> <item>iPhone4</name> <cost>$199.99</cost> </order> --- Response -- HTTP/1.1 201 Created msg-create-next: http://example.com/queues/jms.queue.bar/create/002
You should receive a 201 Created response. If there is a
network failure, just re-POST to the Location header. For new
messages, use the returned msg-create-next
header returned with each response.
POST any new message to the returned
msg-create-next
header.
POST /queues/jms.queue.bar/create/002 Host: example.com Content-Type: application/xml <order> <name>Monica</name> <item>iPad</name> <cost>$499.99</cost> </order> --- Response -- HTTP/1.1 201 Created msg-create-next: http://example.com/queues/jms.queue.bar/create/003
If there ever is a network problem, just repost to the URL
provided in the msg-create-next
header.
How can this work? As you can see, with each successful response,
the HornetQ REST server returns a uniquely generated URL within the
msg-create-next header. This URL is dedicated to the next new message
you want to post. Behind the scenes, the code extracts an identify from
the URL and uses HornetQ's duplicate detection mechanism by setting the
DUPLICATE_DETECTION_ID
property of the JMS message
that is actually posted to the system.
An alternative to this approach is to use the msg-create-with-id
header. This is not an invokable URL, but a URL template. The idea is that
the client provides the DUPLICATE_DETECTION_ID
and creates
it's own create-next
URL. The msg-create-with-id
header looks like this (you've see it in previous examples, but we haven't used it):
msg-create-with-id: http://example.com/queues/jms.queue.bar/create/{id}
You see that it is a regular URL appended with a {id}
. This
{id}
is a pattern matching substring. A client would generate its
DUPLICATE_DETECTION_ID
and replace {id}
with that generated id, then POST to the new URL. The URL the client creates
works exactly like a create-next
URL described earlier. The
response of this POST would also return a new msg-create-next
header. The client can continue to generate its own DUPLICATE_DETECTION_ID, or
use the new URL returned via the msg-create-nex
t header.
The advantage of this approach is that the client does not have to
repost the message. It also only has to come up with a unique
DUPLICATE_DETECTION_ID
once.
By default, posted messages are not durable and will not be
persisted in HornetQ's journal. You can create durable messages by
modifying the default configuration as expressed in Chapter 2 so that
all messages are persisted when sent. Alternatively, you can set a URL
query parameter called durable
to true when you post
your messages to the URLs returned in themsg-create
,
msg-create-with-id
, or msg-create-next
headers. here's an example of that.
POST /queues/jms.queue.bar/create?durable=true Host: example.com Content-Type: application/xml <order> <name>Bill</name> <item>iPhone4</item> <cost>$199.99</cost> </order>
You can set the time to live, expiration, and/or the priority of
the message in the queue or topic by setting an additional query
parameter. The expiration
query parameter is an long
specify the time in milliseconds since epoch (a long date). The
ttl
query parameter is a time in milliseconds you
want the message active. The priority
is another
query parameter with an integer value between 0 and 9 expressing the
priority of the message. i.e.:
POST /queues/jms.queue.bar/create?expiration=30000&priority=3 Host: example.com Content-Type: application/xml <order> <name>Bill</name> <item>iPhone4</item> <cost>$199.99</cost> </order>
There are two different ways to consume messages from a topic or queue. You can wait and have the messaging server push them to you, or you can continuously poll the server yourself to see if messages are available. This chapter discusses the latter. Consuming messages via a pull works almost identically for queues and topics with some minor, but important caveats. To start consuming you must create a consumer resource on the server that is dedicated to your client. Now, this pretty much breaks the stateless principle of REST, but after much prototyping, this is the best way to work most effectively with HornetQ through a REST interface.
You create consumer resources by doing a simple POST to the URL
published by the msg-pull-consumers
response header if you're interacting with a queue, the
msg-pull-subscribers
response header if you're
interacting with a topic. These headers are provided by the main queue or
topic resource discussed in HornetQ REST Interface
Basics. Doing an empty POST to one of these
URLs will create a consumer resource that follows an auto-acknowledge
protocol and, if you're interacting with a topic, creates a temporty
subscription to the topic. If you want to use the acknowledgement protocol
and/or create a durable subscription (topics only), then you must use the
form parameters (application/x-www-form-urlencoded
)
described below.
autoAck
. A value of true
or false
can be given. This defaults to
true
if you do not pass this parameter.
durable
. A value of true
or false
can be given. This defaults to
false
if you do not pass this parameter.
Only available on topics. This specifies whether you want a
durable subscription or not. A durable subscription persists
through server restart.
name
. This is the name of the durable
subscription. If you do not provide this parameter, the name
will be automatically generated by the server. Only usable
on topics.
selector
. This is an optional JMS selector
string. The HornetQ REST interface adds HTTP headers to the
JMS message for REST produced messages. HTTP headers are
prefixed with "http_" and every '-' charactor is converted
to a '$'.
idle-timeout
. For a topic subscription,
idle time in milliseconds in which the consumer connections
will be closed if idle.
delete-when-idle
. Boolean value, If
true, a topic subscription will be deleted (even if it is
durable) when an the idle timeout is reached.
This section focuses on the auto-acknowledge protocol for consuming messages via a pull. Here's a list of the response headers and URLs you'll be interested in.
msg-pull-consumers
. The URL of
a factory resource for creating queue consumer
resources. You will pull from these created resources.
msg-pull-subscriptions
. The URL
of a factory resource for creating topic subscription
resources. You will pull from the created resources.
msg-consume-next
. The URL you
will pull the next message from. This is returned
with every response.
msg-consumer
. This is a URL
pointing back to the consumer or subscription
resource created for the client.
Here is an example of creating an auto-acknowledged queue pull consumer.
Find the pull-consumers URL by doing a HEAD or GET request to the base queue resource.
HEAD /queues/jms.queue.bar HTTP/1.1 Host: example.com --- Response --- HTTP/1.1 200 Ok msg-create: http://example.com/queues/jms.queue.bar/create msg-pull-consumers: http://example.com/queues/jms.queue.bar/pull-consumers msg-push-consumers: http://example.com/queues/jms.queue.bar/push-consumers
Next do an empty POST to the URL returned in the
msg-pull-consumers
header.
POST /queues/jms.queue.bar/pull-consumers HTTP/1.1 Host: example.com --- response --- HTTP/1.1 201 Created Location: http://example.com/queues/jms.queue.bar/pull-consumers/auto-ack/333 msg-consume-next: http://example.com/queues/jms.queue.bar/pull-consumers/auto-ack/333/consume-next-1
The
Location
header points to the JMS
consumer resource that was created on the server. It is good to
remember this URL, although, as you'll see later, it is
transmitted with each response just to remind you.
Creating an auto-acknowledged consumer for a topic is pretty much the same. Here's an example of creating a durable auto-acknowledged topic pull subscription.
Find the
pull-subscriptions
URL by doing
a HEAD or GET request to the base topic resource
HEAD /topics/jms.topic.bar HTTP/1.1 Host: example.com --- Response --- HTTP/1.1 200 Ok msg-create: http://example.com/topics/jms.topic.foo/create msg-pull-subscriptions: http://example.com/topics/jms.topic.foo/pull-subscriptions msg-push-subscriptions: http://example.com/topics/jms.topic.foo/push-subscriptions
Next do a POST to the URL returned in the
msg-pull-subscriptions
header passing in a true
value for the durable
form parameter.
POST /topics/jms.topic.foo/pull-subscriptions HTTP/1.1 Host: example.com Content-Type: application/x-www-form-urlencoded durable=true --- Response --- HTTP/1.1 201 Created Location: http://example.com/topics/jms.topic.foo/pull-subscriptions/auto-ack/222 msg-consume-next: http://example.com/topics/jms.topic.foo/pull-subscriptions/auto-ack/222/consume-next-1
The
Location
header points to the JMS
subscription resource that was created on the server. It is good
to remember this URL, although, as you'll see later, it is
transmitted with each response just to remind you.
After you have created a consumer resource, you are ready to
start pulling messages from the server. Notice that when you created
the consumer for either the queue or topic, the response contained a
msg-consume-next
response header. POST to the URL
contained within this header to consume the next message in the queue
or topic subscription. A successful POST causes the server to extract
a message from the queue or topic subscription, acknowledge it, and
return it to the consuming client. If there are no messages in the
queue or topic subscription, a 503 (Service Unavailable) HTTP code is
returned.
For both successful and unsuccessful posts to the msg-consume-next URL, the response will contain a new msg-consume-next header. You must ALWAYS use this new URL returned within the new msg-consume-next header to consume new messages.
Here's an example of pulling multiple messages from the consumer resource.
Do a POST on the msg-consume-next URL that was returned with the consumer or subscription resource discussed earlier.
POST /queues/jms.queue.bar/pull-consumers/consume-next-1 Host: example.com --- Response --- HTTP/1.1 200 Ok Content-Type: application/xml msg-consume-next: http://example.com/queues/jms.queue.bar/pull-consumers/333/consume-next-2 msg-consumer: http://example.com/queues/jms.queue.bar/pull-consumers/333 <order>...</order>
The POST returns the message consumed from the queue. It also returns a new msg-consume-next link. Use this new link to get the next message. Notice also a msg-consumer response header is returned. This is a URL that points back to the consumer or subscription resource. You will need that to clean up your connection after you are finished using the queue or topic.
The POST returns the message consumed from the queue. It also returns a new msg-consume-next link. Use this new link to get the next message.
POST /queues/jms.queue.bar/pull-consumers/consume-next-2 Host: example.com --- Response --- Http/1.1 503 Service Unavailable Retry-After: 5 msg-consume-next: http://example.com/queues/jms.queue.bar/pull-consumers/333/consume-next-2
In this case, there are no messages in the queue, so we get a 503 response back. As per the HTTP 1.1 spec, a 503 response may return a Retry-After head specifying the time in seconds that you should retry a post. Also notice, that another new msg-consume-next URL is present. Although it probabley is the same URL you used last post, get in the habit of using URLs returned in response headers as future versions of HornetQ REST might be redirecting you or adding additional data to the URL after timeouts like this.
POST to the URL within the last
msg-consume-next
to get the next
message.
POST /queues/jms.queue.bar/pull-consumers/consume-next-2 Host: example.com --- Response --- HTTP/1.1 200 Ok Content-Type: application/xml msg-consume-next: http://example.com/queues/jms.queue.bar/pull-consumers/333/consume-next-3 <order>...</order>
If you experience a network failure and do not know if your post to a msg-consume-next URL was successful or not, just re-do your POST. A POST to a msg-consume-next URL is idempotent, meaning that it will return the same result if you execute on any one msg-consume-next URL more than once. Behind the scenes, the consumer resource caches the last consumed message so that if there is a message failure and you do a re-post, the cached last message will be returned (along with a new msg-consume-next URL). This is the reason why the protocol always requires you to use the next new msg-consume-next URL returned with each response. Information about what state the client is in is embedded within the actual URL.
If the server crashes and you do a POST to the msg-consume-next URL, the server will return a 412 (Preconditions Failed) response code. This is telling you that the URL you are using is out of sync with the server. The response will contain a new msg-consume-next header to invoke on.
If the client crashes there are multiple ways you can recover. If you have remembered the last msg-consume-next link, you can just re-POST to it. If you have remembered the consumer resource URL, you can do a GET or HEAD request to obtain a new msg-consume-next URL. If you have created a topic subscription using the name parameter discussed earlier, you can re-create the consumer. Re-creation will return a msg-consume-next URL you can use. If you cannot do any of these things, you will have to create a new consumer.
The problem with the auto-acknowledge protocol is that if the client or server crashes, it is possible for you to skip messages. The scenario would happen if the server crashes after auto-acknowledging a message and before the client receives the message. If you want more reliable messaging, then you must use the acknowledgement protocol.
The manual acknowledgement protocol is similar to the auto-ack protocol except there is an additional round trip to the server to tell it that you have received the message and that the server can internally ack the message. Here is a list of the respone headers you will be interested in.
msg-pull-consumers
. The URL of a factory resource for creating queue
consumer
resources. You will pull from these created resources
msg-pull-subscriptions
. The URL of a factory resource for creating topic
subscription resources. You will pull from the created
resources.
msg-acknowledge-next
. URL used to obtain the next message in the queue or
topic
subscription. It does not acknowledge the message though.
msg-acknowledgement
. URL used to acknowledge a message.
msg-consumer
. This is a URL pointing back to the consumer or subscription
resource created for the client.
Here is an example of creating an auto-acknowledged queue pull consumer.
Find the pull-consumers URL by doing a HEAD or GET request to the base queue resource.
HEAD /queues/jms.queue.bar HTTP/1.1 Host: example.com --- Response --- HTTP/1.1 200 Ok msg-create: http://example.com/queues/jms.queue.bar/create msg-pull-consumers: http://example.com/queues/jms.queue.bar/pull-consumers msg-push-consumers: http://example.com/queues/jms.queue.bar/push-consumers
Next do a POST to the URL returned in the
msg-pull-consumers
header passing in a
false
value to the
autoAck
form parameter .
POST /queues/jms.queue.bar/pull-consumers HTTP/1.1 Host: example.com Content-Type: application/x-www-form-urlencoded autoAck=false --- response --- HTTP/1.1 201 Created Location: http://example.com/queues/jms.queue.bar/pull-consumers/acknowledged/333 msg-acknowledge-next: http://example.com/queues/jms.queue.bar/pull-consumers/acknowledged/333/acknowledge-next-1
The
Location
header points to the JMS
consumer resource that was created on the server. It is good to
remember this URL, although, as you'll see later, it is
transmitted with each response just to remind you.
Creating an manually-acknowledged consumer for a topic is pretty much the same. Here's an example of creating a durable manually-acknowledged topic pull subscription.
Find the
pull-subscriptions
URL by doing
a HEAD or GET request to the base topic resource
HEAD /topics/jms.topic.bar HTTP/1.1 Host: example.com --- Response --- HTTP/1.1 200 Ok msg-create: http://example.com/topics/jms.topic.foo/create msg-pull-subscriptions: http://example.com/topics/jms.topic.foo/pull-subscriptions msg-push-subscriptions: http://example.com/topics/jms.topic.foo/push-subscriptions
Next do a POST to the URL returned in the
msg-pull-subscriptions
header passing in a
true
value for the
durable
form parameter and a
false
value to the
autoAck
form parameter.
POST /topics/jms.topic.foo/pull-subscriptions HTTP/1.1 Host: example.com Content-Type: application/x-www-form-urlencoded durable=true&autoAck=false --- Response --- HTTP/1.1 201 Created Location: http://example.com/topics/jms.topic.foo/pull-subscriptions/acknowledged/222 msg-acknowledge-next: http://example.com/topics/jms.topic.foo/pull-subscriptions/acknowledged/222/consume-next-1
The
Location
header points to the JMS
subscription resource that was created on the server. It is good
to remember this URL, although, as you'll see later, it is
transmitted with each response just to remind you.
After you have created a consumer resource, you are ready to
start pulling messages from the server. Notice that when you created
the consumer for either the queue or topic, the response contained a
msg-acknowledge-next
response header. POST to the
URL contained within this header to consume the next message in the
queue or topic subscription. If there are no messages in the queue or
topic subscription, a 503 (Service Unavailable) HTTP code is returned.
A successful POST causes the server to extract a message from the
queue or topic subscription and return it to the consuming client. It
does not acknowledge the message though. The response will contain the
acknowledgement
header which you will use to
acknowledge the message.
Here's an example of pulling multiple messages from the consumer resource.
Do a POST on the msg-acknowledge-next URL that was returned with the consumer or subscription resource discussed earlier.
POST /queues/jms.queue.bar/pull-consumers/consume-next-1 Host: example.com --- Response --- HTTP/1.1 200 Ok Content-Type: application/xml msg-acknowledgement: http://example.com/queues/jms.queue.bar/pull-consumers/333/acknowledgement/2 msg-consumer: http://example.com/queues/jms.queue.bar/pull-consumers/333 <order>...</order>
The POST returns the message consumed from the queue. It
also returns amsg-acknowledgemen
t link. You
will use this new link to acknowledge the message. Notice also a
msg-consumer
response header is returned. This
is a URL that points back to the consumer or subscription
resource. You will need that to clean up your connection after you
are finished using the queue or topic.
Acknowledge or unacknowledge the message by doing a POST to
the URL contained in the
msg-acknowledgement
header. You must pass an
acknowledge
form
parameter set to
true
or
false
depending on whether you want to
acknowledge or unacknowledge the message on the server.
POST /queues/jms.queue.bar/pull-consumers/acknowledgement/2 Host: example.com Content-Type: application/x-www-form-urlencoded acknowledge=true --- Response --- Http/1.1 200 Ok msg-acknowledge-next: http://example.com/queues/jms.queue.bar/pull-consumers/333/acknowledge-next-2
Whether you acknowledge or unacknowledge the message, the response will contain a new msg-acknowledge-next header that you must use to obtain the next message.
If you experience a network failure and do not know if your post
to a
msg-acknowledge-next
or
msg-acknowledgement
URL was successful or not, just
re-do your POST. A POST to one of these URLs is idempotent, meaning
that it will return the same result if you re-post. Behind the scenes,
the consumer resource keeps track of its current state. If the last
action was a call tomsg-acknowledge-next
, it will
have the last message cached, so that if a re-post is done, it will
return the message again. Same goes with re-posting to
msg-acknowledgement
. The server remembers its last
state and will return the same results. If you look at the URLs you'll
see that they contain information about the expected current state of
the server. This is how the server knows what the client is
expecting.
If the server crashes and while you are doing a POST to the
msg-acknowledge-next
URL, just re-post. Everything
should reconnect all right. On the other hand, if the server crashes
while you are doing a POST tomsg-acknowledgement
,
the server will return a 412 (Preconditions Failed) response code.
This is telling you that the URL you are using is out of sync with the
server and the message you are acknowledging was probably re-enqueued.
The response will contain a new
msg-acknowledge-next
header to invoke on.
As long as you have "bookmarked" the consumer resource URL
(returned from
Location
header on a create, or the
msg-consumer
header), you can recover from client
crashes by doing a GET or HEAD request on the consumer resource to
obtain what state you are in. If the consumer resource is expecting
you to acknowledge a message, it will return a
msg-acknowledgement
header in the response. If the
consumer resource is expecting you to pull for the next message, the
msg-acknowledge-next
header will be in the
response. With manual acknowledgement you are pretty much guaranteed
to avoid skipped messages. For topic subscriptions that were created
with a name parameter, you do not have to "bookmark" the returned URL.
Instead, you can re-create the consumer resource with the same exact
name. The response will contain the same information as if you did a
GET or HEAD request on the consumer resource.
Unless your queue or topic has a high rate of message flowing
though it, if you use the pull protocol, you're going to be receiving a
lot of 503 responses as you continuously pull the server for new
messages. To alleviate this problem, the HornetQ REST interface provides
the
Accept-Wait
header. This is a generic HTTP
request header that is a hint to the server for how long the client is
willing to wait for a response from the server. The value of this header
is the time in seconds the client is willing to block for. You would
send this request header with your pull requests. Here's an
example:
POST /queues/jms.queue.bar/pull-consumers/consume-next-2 Host: example.com Accept-Wait: 30 --- Response --- HTTP/1.1 200 Ok Content-Type: application/xml msg-consume-next: http://example.com/queues/jms.queue.bar/pull-consumers/333/consume-next-3 <order>...</order>
In this example, we're posting to a msg-consume-next URL and telling the server that we would be willing to block for 30 seconds.
When the client is done with its consumer or topic subscription it
should do an HTTP DELETE call on the consumer URL passed back from the
Location header or the msg-consumer response header. The server will
time out a consumer with the value of
consumer-session-timeout-seconds
configured from
REST configuration, so you
don't have to clean up if you don't want to, but if you are a good kid,
you will clean up your messes. A consumer timeout for durable
subscriptions will not delete the underlying durable JMS subscription
though, only the server-side consumer resource (and underlying JMS
session).
You can configure the HornetQ REST server to push messages to a registered URL either remotely through the REST interface, or by creating a pre-configured XML file for the HornetQ REST server to load at boot time.
Creating a push consumer for a queue first involves creating a very simple XML document. This document tells the server if the push subscription should survive server reboots (is it durable). It must provide a URL to ship the forwarded message to. Finally, you have to provide authentication information if the final endpoint requires authentication. Here's a simple example:
<push-registration> <durable>false</durable> <selector><![CDATA[ SomeAttribute > 1 ]]> </selector> <link rel="push" href="http://somewhere.com" type="application/json" method="PUT"/> <maxRetries>5</maxRetries> <retryWaitMillis>1000</retryWaitMillis> <disableOnFailure>true</disableOnFailure> </push-registration>
The durable
element specifies whether the
registration should be saved to disk so that if there is a server
restart, the push subscription will still work. This element is not
required. If left out it defaults tofalse
. If
durable is set to true, an XML file for the push subscription will be
created within the directory specified by the
queue-push-store-dir
config variable defined in
Chapter 2 (topic-push-store-dir
for topics).
The selector
element is optional and defines a
JMS message selector. You should enclose it within CDATA blocks as some
of the selector characters are illegal XML.
The maxRetries
element specifies how many times
a the server will try to push a message to a URL if there is a
connection failure.
The retryWaitMillis
element specifies how long
to wait before performing a retry.
The
disableOnFailure
element, if set to true,
will disable the registration if all retries have failed. It will not
disable the connection on non-connection-failure issues (like a bad
request for instance). In these cases, the dead letter queue logic of
HornetQ will take over.
The link
element specifies the basis of the
interaction. The href
attribute contains the URL you
want to interact with. It is the only required attribute. The
type
attribute specifies the content-type of what the
push URL is expecting. The method
attribute defines
what HTTP method the server will use when it sends the message to the
server. If it is not provided it defaults to POST. The
rel
attribute is very important and the value of it
triggers different behavior. Here's the values a rel attribute can
have:
destination
. The href URL is assumed to be a queue or topic resource of
another HornetQ REST server. The push registration will initially
do a HEAD request to this URL to obtain a msg-create-with-id
header. It will use this header to push new messages to the
HornetQ REST endpoint reliably. Here's an example:
<push-registration> <link rel="destination" href="http://somewhere.com/queues/jms.queue.foo"/> </push-registration>
template
. In this case, the server is expecting the link element's
href attribute to be a URL expression. The URL expression must
have one and only one URL parameter within it. The server will use
a unique value to create the endpoint URL. Here's an
example:
<push-registration> <link rel="template" href="http://somewhere.com/resources/{id}/messages" method="PUT"/> </push-registration>
In this example, the {id} sub-string is the one and only one URL parameter.
user defined
. If the rel attributes is not destination or template (or is
empty or missing), then the server will send an HTTP message to
the href URL using the HTTP method defined in the method
attribute. Here's an example:
<push-registration> <link href="http://somewhere.com" type="application/json" method="PUT"/> </push-registration>
The push XML for a topic is the same except the root element is
push-topic-registration. (Also remember the selector
element is optional). The rest of the document is the same. Here's an
example of a template registration:
<push-topic-registration> <durable>true</durable> <selector><![CDATA[ SomeAttribute > 1 ]]> </selector> <link rel="template" href="http://somewhere.com/resources/{id}/messages" method="POST"/> </push-topic registration>
Creating a push subscription at runtime involves getting the factory resource URL from the msg-push-consumers header, if the destination is a queue, or msg-push-subscriptions header, if the destination is a topic. Here's an example of creating a push registration for a queue:
First do a HEAD request to the queue resource:
HEAD /queues/jms.queue.bar HTTP/1.1 Host: example.com --- Response --- HTTP/1.1 200 Ok msg-create: http://example.com/queues/jms.queue.bar/create msg-pull-consumers: http://example.com/queues/jms.queue.bar/pull-consumers msg-push-consumers: http://example.com/queues/jms.queue.bar/push-consumers
Next POST your subscription XML to the URL returned from msg-push-consumers header
POST /queues/jms.queue.bar/push-consumers Host: example.com Content-Type: application/xml <push-registration> <link rel="destination" href="http://somewhere.com/queues/jms.queue.foo"/> </push-registration> --- Response --- HTTP/1.1 201 Created Location: http://example.com/queues/jms.queue.bar/push-consumers/1-333-1212
The Location header contains the URL for the created resource. If you want to unregister this, then do a HTTP DELETE on this URL.
Here's an example of creating a push registration for a topic:
First do a HEAD request to the topic resource:
HEAD /topics/jms.topic.bar HTTP/1.1 Host: example.com --- Response --- HTTP/1.1 200 Ok msg-create: http://example.com/topics/jms.topic.bar/create msg-pull-subscriptions: http://example.com/topics/jms.topic.bar/pull-subscriptions msg-push-subscriptions: http://example.com/topics/jms.topic.bar/push-subscriptions
Next POST your subscription XML to the URL returned from msg-push-subscriptions header
POST /topics/jms.topic.bar/push-subscriptions Host: example.com Content-Type: application/xml <push-registration> <link rel="template" href="http://somewhere.com/resources/{id}"/> </push-registration> --- Response --- HTTP/1.1 201 Created Location: http://example.com/topics/jms.topic.bar/push-subscriptions/1-333-1212
The Location header contains the URL for the created resource. If you want to unregister this, then do a HTTP DELETE on this URL.
You can create a push XML file yourself if you do not want to go through the REST interface to create a push subscription. There is some additional information you need to provide though. First, in the root element, you must define a unique id attribute. You must also define a destination element to specify the queue you should register a consumer with. For a topic, the destination element is the name of the subscription that will be reated. For a topic, you must also specify the topic name within the topic element.
Here's an example of a hand-created queue registration. This file must go in the directory specified by the queue-push-store-dir config variable defined in Chapter 2:
<push-registration id="111"> <destination>jms.queue.bar</destination> <durable>true</durable> <link rel="template" href="http://somewhere.com/resources/{id}/messages" method="PUT"/> </push-registration>
Here's an example of a hand-created topic registration. This file must go in the directory specified by the topic-push-store-dir config variable defined in Chapter 2:
<push-topic-registration id="112"> <destination>my-subscription-1</destination <durable>true</durable> <link rel="template" href="http://somewhere.com/resources/{id}/messages" method="PUT"/> <topic>jms.topic.foo</topic> </push-topic-registration>
Push subscriptions only support BASIC and DIGEST authentication out of the box. Here is an example of adding BASIC authentication:
<push-topic-registration> <durable>true</durable> <link rel="template" href="http://somewhere.com/resources/{id}/messages" method="POST"/> <authentication> <basic-auth> <username>guest</username> <password>geheim</password> </basic-auth> </authentication> </push-topic registration>
For DIGEST, just replace basic-auth with digest-auth.
For other authentication mechanisms, you can register headers you want transmitted with each request. Use the header element with the name attribute representing the name of the header. Here's what custom headers might look like:
<push-topic-registration> <durable>true</durable> <link rel="template" href="http://somewhere.com/resources/{id}/messages" method="POST"/> <header name="secret-header">jfdiwe3321</header> </push-topic registration>
You can create a durable queue or topic through the REST interface. Currently you cannot create a temporary queue or topic. To create a queue you do a POST to the relative URL /queues with an XML representation of the queue. The XML syntax is the same queue syntax that you would specify in hornetq-jms.xml if you were creating a queue there. For example:
POST /queues Host: example.com Content-Type: application/hornetq.jms.queue+xml <queue name="testQueue"> <durable>true</durable> </queue> --- Response --- HTTP/1.1 201 Created Location: http://example.com/queues/jms.queue.testQueue
Notice that the Content-Type is application/hornetq.jms.queue+xml.
Here's what creating a topic would look like:
POST /topics Host: example.com Content-Type: application/hornetq.jms.topic+xml <topic name="testTopic"> </topic> --- Response --- HTTP/1.1 201 Created Location: http://example.com/topics/jms.topic.testTopic
Securing the HornetQ REST interface is very simple with the JBoss Application Server. You turn on authentication for all URLs within your WAR's web.xml, and let the user Principal to propagate to HornetQ. This only works if you are using the JBossSecurityManager with HornetQ. See the HornetQ documentation for more details.
To secure the HornetQ REST interface in other environments you must role your own security by specifying security constraints with your web.xml for every path of every queue and topic you have deployed. Here is a list of URI patterns:
Table 43.1.
/queues | secure the POST operation to secure queue creation |
/queues/{queue-name} | secure the GET HEAD operation to getting information about the queue. |
/queues/{queue-name}/create/* | secure this URL pattern for producing messages. |
/queues/{queue-name}/pull-consumers/* | secure this URL pattern for pulling messages messages. |
/queues/{queue-name}/push-consumers/* | secure this URL pattern for pushing messages. |
/topics | secure the POST operation to secure topic creation |
/topics/{topic-name} | secure the GET HEAD operation to getting information about the topic. |
/topics/{topic-name}/create/* | secure this URL pattern for producing messages. |
/topics/{topic-name}/pull-subscriptions/* | secure this URL pattern for pulling messages messages. |
/topics/{topic-name}/push-subscriptions/* | secure this URL pattern for pushing messages. |
The HornetQ REST interface supports mixing JMS and REST producres and consumers. You can send an ObjectMessage through a JMS Producer, and have a REST client consume it. You can have a REST client POST a message to a topic and have a JMS Consumer receive it. Some simple transformations are supported if you have the correct RESTEasy providers installed.
If you have a JMS producer, the HornetQ REST interface only supports ObjectMessage type. If the JMS producer is aware that there may be REST consumers, it should set a JMS property to specify what Content-Type the Java object should be translated into by REST clients. The HornetQ REST server will use RESTEasy content handlers (MessageBodyReader/Writers) to transform the Java object to the type desired. Here's an example of a JMS producer setting the content type of the message.
ObjectMessage message = session.createObjectMessage(); message.setStringProperty(org.hornetq.rest.HttpHeaderProperty.CONTENT_TYPE, "application/xml");
If the JMS producer does not set the content-type, then this information must be obtained from the REST consumer. If it is a pull consumer, then the REST client should send an Accept header with the desired media types it wants to convert the Java object into. If the REST client is a push registration, then the type attribute of the link element of the push registration should be set to the desired type.
If you have a REST client producing messages and a JMS consumer, HornetQ REST has a simple helper class for you to transform the HTTP body to a Java object. Here's some example code:
public void onMessage(Message message) { MyType obj = org.hornetq.rest.Jms.getEntity(message, MyType.class); }
The way the
getEntity()
method works is that if
the message is an ObjectMessage, it will try to extract the desired type
from it like any other JMS message. If a REST producer sent the message,
then the method uses RESTEasy to convert the HTTP body to the Java
object you want. See the Javadoc of this class for more helper
methods.
HornetQ is designed as set of simple Plain Old Java Objects (POJOs). This means HornetQ can be instantiated and run in any dependency injection framework such as JBoss Microcontainer, Spring or Google Guice. It also means that if you have an application that could use messaging functionality internally, then it can directly instantiate HornetQ clients and servers in its own application code to perform that functionality. We call this embedding HornetQ.
Examples of applications that might want to do this include any application that needs very high performance, transactional, persistent messaging but doesn't want the hassle of writing it all from scratch.
Embedding HornetQ can be done in very few easy steps. Instantiate the configuration object, instantiate the server, start it, and you have a HornetQ running in your virtual machine. It's as simple and easy as that.
The simplest way to embed HornetQ is to use the embedded wrapper classes and configure HornetQ through its configuration files. There are two different helper classes for this depending on whether your using the HornetQ Core API or JMS.
For instantiating a core HornetQ Server only, the steps are pretty
simple. The example requires that you have defined a configuration file
hornetq-configuration.xml
in your
classpath:
import org.hornetq.core.server.embedded.EmbeddedHornetQ; ... EmbeddedHornetQ embedded = new EmbeddedHornetQ(); embedded.start(); ClientSessionFactory nettyFactory = HornetQClient.createClientSessionFactory( new TransportConfiguration( InVMConnectorFactory.class.getName())); ClientSession session = factory.createSession(); session.createQueue("example", "example", true); ClientProducer producer = session.createProducer("example"); ClientMessage message = session.createMessage(true); message.getBody().writeString("Hello"); producer.send(message); session.start(); ClientConsumer consumer = session.createConsumer("example"); ClientMessage msgReceived = consumer.receive(); System.out.println("message = " + msgReceived.getBody().readString()); session.close();
The EmbeddedHornetQ
class has a
few additional setter methods that allow you to specify a different
config file name as well as other properties. See the javadocs for this
class for more details.
JMS embedding is simple as well. This example requires that you
have defined the config files
hornetq-configuration.xml
,
hornetq-jms.xml
, and a
hornetq-users.xml
if you have security enabled. Let's
also assume that a queue and connection factory has been defined in the
hornetq-jms.xml
config file.
import org.hornetq.jms.server.embedded.EmbeddedJMS; ... EmbeddedJMS jms = new EmbeddedJMS(); jms.start(); // This assumes we have configured hornetq-jms.xml with the appropriate config information ConnectionFactory connectionFactory = jms.lookup("ConnectionFactory"); Destination destination = jms.lookup("/example/queue"); ... regular JMS code ...
By default, the EmbeddedJMS
class will store component entries defined within your
hornetq-jms.xml
file in an internal concurrent hash
map. The EmbeddedJMS.lookup()
method returns
components stored in this map. If you want to use JNDI, call the
EmbeddedJMS.setContext()
method with the root JNDI
context you want your components bound into. See the javadocs for this
class for more details on other config options.
You can follow this step-by-step guide to programmatically embed the core, non-JMS HornetQ Server instance:
Create the configuration object - this contains configuration information for a HornetQ instance. The setter methods of this class allow you to programmitcally set configuration options as describe in the Section 49.1, “Server Configuration” section.
The acceptors are configured through
ConfigurationImpl
. Just add the
NettyAcceptorFactory
on the transports the same way you
would through the main configuration file.
import org.hornetq.core.config.Configuration; import org.hornetq.core.config.impl.ConfigurationImpl; ... Configuration config = new ConfigurationImpl(); HashSet<TransportConfiguration> transports = new HashSet<TransportConfiguration>(); transports.add(new TransportConfiguration(NettyAcceptorFactory.class.getName())); transports.add(new TransportConfiguration(InVMAcceptorFactory.class.getName())); config.setAcceptorConfigurations(transports);
You need to instantiate an instance of
org.hornetq.api.core.server.embedded.EmbeddedHornetQ
and add the configuration object to it.
import org.hornetq.api.core.server.HornetQ; import org.hornetq.core.server.embedded.EmbeddedHornetQ; ... EmbeddedHornetQ server = new EmbeddedHornetQ(); server.setConfiguration(config); server.start();
You also have the option of instantiating
HornetQServerImpl
directly:
HornetQServer server = new HornetQServerImpl(config); server.start();
For JMS POJO instantiation, you work with the EmbeddedJMS class instead as described earlier. First you define the configuration programmatically for your ConnectionFactory and Destination objects, then set the JmsConfiguration property of the EmbeddedJMS class. Here is an example of this:
// Step 1. Create HornetQ core configuration, and set the properties accordingly Configuration configuration = new ConfigurationImpl(); configuration.setPersistenceEnabled(false); configuration.setSecurityEnabled(false); configuration.getAcceptorConfigurations().add(new TransportConfiguration(NettyAcceptorFactory.class.getName())); // Step 2. Create the JMS configuration JMSConfiguration jmsConfig = new JMSConfigurationImpl(); // Step 3. Configure the JMS ConnectionFactory TransportConfiguration connectorConfig = new TransportConfiguration(NettyConnectorFactory.class.getName()); ConnectionFactoryConfiguration cfConfig = new ConnectionFactoryConfigurationImpl("cf", connectorConfig, "/cf"); jmsConfig.getConnectionFactoryConfigurations().add(cfConfig); // Step 4. Configure the JMS Queue JMSQueueConfiguration queueConfig = new JMSQueueConfigurationImpl("queue1", null, false, "/queue/queue1"); jmsConfig.getQueueConfigurations().add(queueConfig); // Step 5. Start the JMS Server using the HornetQ core server and the JMS configuration EmbeddedJMS jmsServer = new EmbeddedJMS(); jmsServer.setConfiguration(configuration); jmsServer.setJmsConfiguration(jmsConfig); jmsServer.start();
Please see Section 11.1.20, “Embedded” for an example which shows how to setup and run HornetQ embedded with JMS.
You may also choose to use a dependency injection framework such as JBoss Micro Container™ or Spring Framework™. See Chapter 45, Spring Integration for more details on Spring and HornetQ, but here's how you would do things with the JBoss Micro Contaier.
HornetQ standalone uses JBoss Micro Container as the injection
framework. HornetQBootstrapServer
and
hornetq-beans.xml
which are part of the HornetQ
distribution provide a very complete implementation of what's needed to
bootstrap the server using JBoss Micro Container.
When using JBoss Micro Container, you need to provide an XML file
declaring the HornetQServer
and
Configuration
object, you can also inject a security
manager and a MBean server if you want, but those are optional.
A very basic XML Bean declaration for the JBoss Micro Container would be:
<?xml version="1.0" encoding="UTF-8"?> <deployment xmlns="urn:jboss:bean-deployer:2.0"> <!-- The core configuration --> <bean name="Configuration" class="org.hornetq.core.config.impl.FileConfiguration"> </bean> <!-- The core server --> <bean name="HornetQServer" class="org.hornetq.core.server.impl.HornetQServerImpl"> <constructor> <parameter> <inject bean="Configuration"/> </parameter> </constructor> </bean> </deployment>
HornetQBootstrapServer
provides an easy
encapsulation of JBoss Micro Container.
HornetQBootstrapServer bootStrap = new HornetQBootstrapServer(new String[] {"hornetq-beans.xml"}); bootStrap.run();
HornetQ provides a simple bootstrap class,
org.hornetq.integration.spring.SpringJmsBootstrap
, for
integration with Spring. To use it, you configure HornetQ as you always
would, through its various configuration files like
hornetq-configuration.xml
,
hornetq-jms.xml
, and
hornetq-users.xml
. The Spring helper class starts the
HornetQ server and adds any factories or destinations configured within
hornetq-jms.xml
directly into the namespace of the Spring
context. Let's take this hornetq-jms.xml
file for
instance:
<configuration xmlns="urn:hornetq" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="urn:hornetq /schema/hornetq-jms.xsd"> <!--the connection factory used by the example--> <connection-factory name="ConnectionFactory"> <connectors> <connector-ref connector-name="in-vm"/> </connectors> <entries> <entry name="ConnectionFactory"/> </entries> </connection-factory> <!--the queue used by the example--> <queue name="exampleQueue"> <entry name="/queue/exampleQueue"/> </queue> </configuration>
Here we've specified a
javax.jms.ConnectionFactory
we want bound to a
ConnectionFactory
entry as well as a queue destination
bound to a /queue/exampleQueue
entry. Using the
SpringJmsBootStrap
bean will automatically populate the
Spring context with references to those beans so that you can use them.
Below is an example Spring JMS bean file taking advantage of this
feature:
<beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd"> <bean id="EmbeddedJms" class="org.hornetq.integration.spring.SpringJmsBootstrap" init-method="start"/> <bean id="listener" class="org.hornetq.tests.integration.spring.ExampleListener"/> <bean id="listenerContainer" class="org.springframework.jms.listener.DefaultMessageListenerContainer"> <property name="connectionFactory" ref="ConnectionFactory"/> <property name="destination" ref="/queue/exampleQueue"/> <property name="messageListener" ref="listener"/> </bean> </beans>
As you can see, the
listenerContainer
bean references the components defined
in the hornetq-jms.xml
file. The
SpringJmsBootstrap
class extends the EmbeddedJMS class
talked about in Section 44.1.2, “JMS API” and the same defaults and
configuration options apply. Also notice that an
init-method
must be declared with a start value so that
the bean's lifecycle is executed. See the javadocs for more details on other
properties of the bean class.
HornetQ supports interceptors to intercept packets entering and exiting the server. Incoming and outgoing interceptors are be called for any packet entering or exiting the server respectively. This allows custom code to be executed, e.g. for auditing packets, filtering or other reasons. Interceptors can change the packets they intercept. This makes interceptors powerful, but also potentially dangerous.
An interceptor must implement the Interceptor interface
:
package org.hornetq.api.core.interceptor; public interface Interceptor { boolean intercept(Packet packet, RemotingConnection connection) throws HornetQException; }
The returned boolean value is important:
if true
is returned, the process continues normally
if false
is returned, the process is aborted, no other interceptors
will be called and the packet will not be processed further by the server.
Both incoming and outgoing interceptors are configured in
hornetq-configuration.xml
:
<remoting-incoming-interceptors> <class-name>org.hornetq.jms.example.LoginInterceptor</class-name> <class-name>org.hornetq.jms.example.AdditionalPropertyInterceptor</class-name> </remoting-incoming-interceptors>
<remoting-outgoing-interceptors> <class-name>org.hornetq.jms.example.LogoutInterceptor</class-name> <class-name>org.hornetq.jms.example.AdditionalPropertyInterceptor</class-name> </remoting-outgoing-interceptors>
The interceptors classes (and their dependencies) must be added to the server classpath to be properly instantiated and called.
The interceptors can also be run on the client side to intercept packets either sent by the
client to the server or by the server to the client. This is done by adding the interceptor to
the ServerLocator
with the addIncomingInterceptor(Interceptor)
or
addOutgoingInterceptor(Interceptor)
methods.
As noted above, if an interceptor returns false
then the sending of the
packet is aborted which means that no other interceptors are be called and the packet is not
be processed further by the client. Typically this process happens transparently to the client
(i.e. it has no idea if a packet was aborted or not). However, in the case of an outgoing packet
that is sent in a blocking
fashion a HornetQException
will
be thrown to the caller. The exception is thrown because blocking sends provide reliability and
it is considered an error for them not to succeed. Blocking
sends occurs when,
for example, an application invokes setBlockOnNonDurableSend(true)
or
setBlockOnDurableSend(true)
on its ServerLocator
or if an
application is using a JMS connection factory retrieved from JNDI that has either
block-on-durable-send
or block-on-non-durable-send
set to true
. Blocking is also used for packets dealing with transactions (e.g.
commit, roll-back, etc.). The HornetQException
thrown will contain the name
of the interceptor that returned false.
As on the server, the client interceptor classes (and their dependencies) must be added to the classpath to be properly instantiated and invoked.
See Section 11.1.26, “Interceptor” for an example which shows how to use interceptors to add properties to a message on the server.
Stomp is a text-orientated wire protocol that allows Stomp clients to communicate with Stomp Brokers. HornetQ now supports both Stomp 1.0 and Stomp 1.1.
Stomp clients are available for several languages and platforms making it a good choice for interoperability.
HornetQ provides native support for Stomp. To be able to send and receive Stomp messages,
you must configure a NettyAcceptor
with a protocol
parameter set to stomp
:
<acceptor name="stomp-acceptor"> <factory-class>org.hornetq.core.remoting.impl.netty.NettyAcceptorFactory</factory-class> <param key="protocol" value="stomp"/> <param key="port" value="61613"/> </acceptor>
With this configuration, HornetQ will accept Stomp connections on
the port 61613
(which is the default port of the Stomp brokers).
See the stomp
example which shows how to configure a HornetQ server with Stomp.
Message acknowledgements are not transactional. The ACK frame can not be part of a transaction
(it will be ignored if its transaction
header is set).
HornetQ currently doesn't support virtual hosting, which means the 'host' header in CONNECT fram will be ignored.
HornetQ specifies a minimum value for both client and server heart-beat intervals. The minimum interval for both client and server heartbeats is 500 milliseconds. That means if a client sends a CONNECT frame with heartbeat values lower than 500, the server will defaults the value to 500 milliseconds regardless the values of the 'heart-beat' header in the frame.
Stomp clients deals with destinations when sending messages and subscribing. Destination names are simply strings which are mapped to some form of destination on the server - how the server translates these is left to the server implementation.
In HornetQ, these destinations are mapped to addresses and queues.
When a Stomp client sends a message (using a SEND
frame), the specified destination is mapped
to an address.
When a Stomp client subscribes (or unsubscribes) for a destination (using a SUBSCRIBE
or UNSUBSCRIBE
frame), the destination is mapped to a HornetQ queue.
Well behaved STOMP clients will always send a DISCONNECT frame before closing their connections. In this case the server will clear up any server side resources such as sessions and consumers synchronously. However if STOMP clients exit without sending a DISCONNECT frame or if they crash the server will have no way of knowing immediately whether the client is still alive or not. STOMP connections therefore default to a connection-ttl value of 1 minute (see chapter on connection-ttl for more information. This value can be overridden using connection-ttl-override.
If you need a specific connection-ttl for your stomp connections without affecting the connection-ttl-override setting, you can configure your stomp acceptor with the "connection-ttl" property, which is used to set the ttl for connections that are created from that acceptor. For example:
<acceptor name="stomp-acceptor"> <factory-class>org.hornetq.core.remoting.impl.netty.NettyAcceptorFactory</factory-class> <param key="protocol" value="stomp"/> <param key="port" value="61613"/> <param key="connection-ttl" value="20000"/> </acceptor>
The above configuration will make sure that any stomp connection that is created from that acceptor will have its connection-ttl set to 20 seconds.
Please note that the STOMP protocol version 1.0 does not contain any heartbeat frame. It is therefore the user's
responsibility to make sure data is sent within connection-ttl or the server will assume the client is dead and clean up server
side resources. With Stomp 1.1
users can use heart-beats to maintain the life cycle of stomp
connections.
As explained in Chapter 9, Mapping JMS Concepts to the Core API, JMS destinations are also mapped to HornetQ addresses and queues. If you want to use Stomp to send messages to JMS destinations, the Stomp destinations must follow the same convention:
send or subscribe to a JMS Queue by prepending the queue name by jms.queue.
.
For example, to send a message to the orders
JMS Queue, the Stomp client must send the frame:
SEND destination:jms.queue.orders hello queue orders ^@
send or subscribe to a JMS Topic by prepending the topic name by jms.topic.
.
For example to subscribe to the stocks
JMS Topic, the Stomp client must send the frame:
SUBSCRIBE destination:jms.topic.stocks ^@
Stomp is mainly a text-orientated protocol. To make it simpler to interoperate with JMS and HornetQ Core API,
our Stomp implementation checks for presence of the content-length
header to decide how to map a Stomp message
to a JMS Message or a Core message.
If the Stomp message does not have a content-length
header, it will be mapped to a JMS TextMessage
or a Core message with a single nullable SimpleString in the body buffer.
Alternatively, if the Stomp message has a content-length
header,
it will be mapped to a JMS BytesMessage
or a Core message with a byte[] in the body buffer.
The same logic applies when mapping a JMS message or a Core message to Stomp. A Stomp client can check the presence
of the content-length
header to determine the type of the message body (String or bytes).
When receiving Stomp messages via a JMS consumer or a QueueBrowser, the messages have
no properties like JMSMessageID by default. However this may bring some inconvenience to
clients who wants an ID for their purpose. HornetQ Stomp provides a parameter to enable
message ID on each incoming Stomp message. If you want each Stomp message to have a unique ID,
just set the stomp-enable-message-id
to true. For example:
<acceptor name="stomp-acceptor"> <factory-class>org.hornetq.core.remoting.impl.netty.NettyAcceptorFactory</factory-class> <param key="protocol" value="stomp"/> <param key="port" value="61613"/> <param key="stomp-enable-message-id" value="true"/> </acceptor>
When the server starts with the above setting, each stomp message sent through this
acceptor will have an extra property added. The property key is
hq-message-id
and the value is a String representation of a long type internal
message id prefixed with "STOMP
", like:
hq-message-id : STOMP12345
If stomp-enable-message-id
is not specified in the configuration, default
is false
.
HornetQ also support Stomp over Web Sockets. Modern web browser which support Web Sockets can send and receive Stomp messages from HornetQ.
To enable Stomp over Web Sockets, you must configure a NettyAcceptor
with a protocol
parameter set to stomp_ws
:
<acceptor name="stomp-ws-acceptor"> <factory-class>org.hornetq.core.remoting.impl.netty.NettyAcceptorFactory</factory-class> <param key="protocol" value="stomp_ws"/> <param key="port" value="61614"/> </acceptor>
With this configuration, HornetQ will accept Stomp connections over Web Sockets on
the port 61614
with the URL path /stomp
.
Web browser can then connect to ws://<server>:61614/stomp
using a Web Socket to send and receive Stomp
messages.
A companion JavaScript library to ease client-side development is available from GitHub (please see its documentation for a complete description).
The stomp-websockets
example shows how to configure HornetQ server to have web browsers and Java
applications exchanges messages on a JMS topic.
StompConnect is a server that can act as a Stomp broker and proxy the Stomp protocol to the standard JMS API. Consequently, using StompConnect it is possible to turn HornetQ into a Stomp Broker and use any of the available stomp clients. These include clients written in C, C++, c# and .net etc.
To run StompConnect first start the HornetQ server and make sure that it is using JNDI.
Stomp requires the file jndi.properties
to be available on the
classpath. This should look something like:
java.naming.factory.initial=org.jnp.interfaces.NamingContextFactory java.naming.provider.url=jnp://localhost:1099 java.naming.factory.url.pkgs=org.jboss.naming:org.jnp.interfaces
Make sure this file is in the classpath along with the StompConnect jar and the
HornetQ jars and simply run java org.codehaus.stomp.jms.Main
.
In this chapter we'll discuss how to tune HornetQ for optimum performance.
Put the message journal on its own physical volume. If the disk is shared with other processes e.g. transaction co-ordinator, database or other journals which are also reading and writing from it, then this may greatly reduce performance since the disk head may be skipping all over the place between the different files. One of the advantages of an append only journal is that disk head movement is minimised - this advantage is destroyed if the disk is shared. If you're using paging or large messages make sure they're ideally put on separate volumes too.
Minimum number of journal files. Set journal-min-files
to a
number of files that would fit your average sustainable rate. If you see new
files being created on the journal data directory too often, i.e. lots of data
is being persisted, you need to increase the minimal number of files, this way
the journal would reuse more files instead of creating new data files.
Journal file size. The journal file size should be aligned to the capacity of a cylinder on the disk. The default value 10MiB should be enough on most systems.
Use AIO journal. If using Linux, try to keep your journal type as AIO. AIO will scale better than Java NIO.
Tune journal-buffer-timeout
. The timeout can be increased
to increase throughput at the expense of latency.
If you're running AIO you might be able to get some better performance by
increasing journal-max-io
. DO NOT change this parameter if
you are running NIO.
There are a few areas where some tweaks can be done if you are using the JMS API
Disable message id. Use the setDisableMessageID()
method on
the MessageProducer
class to disable message ids if you don't
need them. This decreases the size of the message and also avoids the overhead
of creating a unique ID.
Disable message timestamp. Use the setDisableMessageTimeStamp()
method on the MessageProducer
class to disable message timestamps if you don't
need them.
Avoid ObjectMessage
. ObjectMessage
is
convenient but it comes at a cost. The body of a ObjectMessage
uses Java serialization to serialize it to bytes.
The Java serialized form of even small objects is very verbose so takes up a lot
of space on the wire, also Java serialization is slow compared to custom
marshalling techniques. Only use ObjectMessage
if you really
can't use one of the other message types, i.e. if you really don't know the type
of the payload until run-time.
Avoid AUTO_ACKNOWLEDGE
. AUTO_ACKNOWLEDGE
mode requires an acknowledgement to be sent from the server for each message
received on the client, this means more traffic on the network. If you can, use
DUPS_OK_ACKNOWLEDGE
or use CLIENT_ACKNOWLEDGE
or a transacted session and batch up many
acknowledgements with one acknowledge/commit.
Avoid durable messages. By default JMS messages are durable. If you don't really need durable messages then set them to be non-durable. Durable messages incur a lot more overhead in persisting them to storage.
Batch many sends or acknowledgements in a single transaction. HornetQ will only require a network round trip on the commit, not on every send or acknowledgement.
There are various other places in HornetQ where we can perform some tuning:
Use Asynchronous Send Acknowledgements. If you need to send durable messages non transactionally and you need a guarantee that they have reached the server by the time the call to send() returns, don't set durable messages to be sent blocking, instead use asynchronous send acknowledgements to get your acknowledgements of send back in a separate stream, see Chapter 20, Guarantees of sends and commits for more information on this.
Use pre-acknowledge mode. With pre-acknowledge mode, messages are acknowledged
before
they are sent to the client. This reduces the
amount of acknowledgement traffic on the wire. For more information on this, see
Chapter 29, Extra Acknowledge Modes.
Disable security. You may get a small performance boost by disabling security
by setting the security-enabled
parameter to false
in hornetq-configuration.xml
.
Disable persistence. If you don't need message persistence, turn it off
altogether by setting persistence-enabled
to false in
hornetq-configuration.xml
.
Sync transactions lazily. Setting journal-sync-transactional
to false
in
hornetq-configuration.xml
can give you better
transactional persistent performance at the expense of some possibility of loss
of transactions on failure. See Chapter 20, Guarantees of sends and commits for more
information.
Sync non transactional lazily. Setting journal-sync-non-transactional
to false
in
hornetq-configuration.xml
can give you better
non-transactional persistent performance at the expense of some possibility of
loss of durable messages on failure. See Chapter 20, Guarantees of sends and commits for
more information.
Send messages non blocking. Setting block-on-durable-send
and block-on-non-durable-send
to false
in
hornetq-jms.xml
(if you're using JMS and JNDI) or
directly on the ClientSessionFactory. This means you don't have to wait a whole
network round trip for every message sent. See Chapter 20, Guarantees of sends and commits
for more information.
If you have very fast consumers, you can increase consumer-window-size. This effectively disables consumer flow control.
Socket NIO vs Socket Old IO. By default HornetQ uses old (blocking) on the server and the client side (see the chapter on configuring transports for more information Chapter 16, Configuring the Transport). NIO is much more scalable but can give you some latency hit compared to old blocking IO. If you need to be able to service many thousands of connections on the server, then you should make sure you're using NIO on the server. However, if don't expect many thousands of connections on the server you can keep the server acceptors using old IO, and might get a small performance advantage.
Use the core API not JMS. Using the JMS API you will have slightly lower
performance than using the core API, since all JMS operations need to be
translated into core operations before the server can handle them. If using the
core API try to use methods that take SimpleString
as much as
possible. SimpleString
, unlike java.lang.String does not
require copying before it is written to the wire, so if you re-use SimpleString
instances between calls then you can avoid some
unnecessary copying.
TCP buffer sizes. If you have a fast network and fast machines you may get a performance boost by increasing the TCP send and receive buffer sizes. See the Chapter 16, Configuring the Transport for more information on this.
Note that some operating systems like later versions of Linux include TCP auto-tuning and setting TCP buffer sizes manually can prevent auto-tune from working and actually give you worse performance!
Increase limit on file handles on the server. If you expect a lot of concurrent connections on your servers, or if clients are rapidly opening and closing connections, you should make sure the user running the server has permission to create sufficient file handles.
This varies from operating system to operating system. On Linux systems you
can increase the number of allowable open file handles in the file /etc/security/limits.conf
e.g. add the lines
serveruser soft nofile 20000 serveruser hard nofile 20000
This would allow up to 20000 file handles to be open by the user serveruser
.
Use batch-delay
and set direct-deliver
to false for the best throughput for very small messages. HornetQ comes with a
preconfigured connector/acceptor pair (netty-throughput
) in
hornetq-configuration.xml
and JMS connection factory
(ThroughputConnectionFactory
) in hornetq-jms.xml
which can be used to give the very best
throughput, especially for small messages. See the Chapter 16, Configuring the Transport for more information on this.
We highly recommend you use the latest Java JVM for the best performance. We test internally using the Sun JVM, so some of these tunings won't apply to JDKs from other providers (e.g. IBM or JRockit)
Garbage collection. For smooth server operation we recommend using a parallel
garbage collection algorithm, e.g. using the JVM argument -XX:+UseParallelGC
on Sun JDKs.
Memory settings. Give as much memory as you can to the server. HornetQ can run
in low memory by using paging (described in Chapter 24, Paging) but if it
can run with all queues in RAM this will improve performance. The amount of
memory you require will depend on the size and number of your queues and the
size and number of your messages. Use the JVM arguments -Xms
and -Xmx
to set server available RAM. We recommend setting
them to the same high value.
Aggressive options. Different JVMs provide different sets of JVM tuning
parameters, for the Sun Hotspot JVM the full list of options is available here. We recommend at least using -XX:+AggressiveOpts
and
-XX:+UseFastAccessorMethods
. You may get some mileage with the
other tuning parameters depending on your OS platform and application usage
patterns.
Re-use connections / sessions / consumers / producers. Probably the most common messaging anti-pattern we see is users who create a new connection/session/producer for every message they send or every message they consume. This is a poor use of resources. These objects take time to create and may involve several network round trips. Always re-use them.
Some popular libraries such as the Spring JMS Template are known to use these anti-patterns. If you're using Spring JMS Template and you're getting poor performance you know why. Don't blame HornetQ! The Spring JMS Template can only safely be used in an app server which caches JMS sessions (e.g. using JCA), and only then for sending messages. It cannot be safely be used for synchronously consuming messages, even in an app server.
Avoid fat messages. Verbose formats such as XML take up a lot of space on the wire and performance will suffer as result. Avoid XML in message bodies if you can.
Don't create temporary queues for each request. This common anti-pattern involves the temporary queue request-response pattern. With the temporary queue request-response pattern a message is sent to a target and a reply-to header is set with the address of a local temporary queue. When the recipient receives the message they process it then send back a response to the address specified in the reply-to. A common mistake made with this pattern is to create a new temporary queue on each message sent. This will drastically reduce performance. Instead the temporary queue should be re-used for many requests.
Don't use Message-Driven Beans for the sake of it. As soon as you start using MDBs you are greatly increasing the codepath for each message received compared to a straightforward message consumer, since a lot of extra application server code is executed. Ask yourself do you really need MDBs? Can you accomplish the same task using just a normal message consumer?
This section is a quick index for looking up configuration. Click on the element name to go to the specific chapter.
This is the main core server configuration file.
Table 49.1. Server Configuration
Element Name | Element Type | Description | Default |
---|---|---|---|
allow-failback | Boolean | Will this server automatically shutdown if the original live server comes back up | false |
backup | Boolean | Is this server a backup server | false |
bindings-directory | String | the directory to store the persisted bindings to | data/bindings |
clustered | Boolean | Deprecated. This option is ignored. If the configuration has at least one cluster-configuration, the server will be clustered | false |
connection-ttl-override | Long | if set, this will override how long (in ms) to keep a connection alive without receiving a ping. | -1 |
create-bindings-dir | Boolean | true means that the server will create the bindings directory on start up | true |
create-journal-dir | Boolean | true means that the journal directory will be created | true |
Continued..
file-deployment-enabled | Boolean | true means that the server will load configuration from the configuration files | true |
failover-on-shutdown | Boolean | Will this backup server come live on a normal server shutdown | false |
id-cache-size | Integer | the size of the cache for pre creating message id's | 2000 |
journal-buffer-size | Long | The size of the internal buffer on the journal. | 128 KiB |
journal-buffer-timeout | Long | The timeout (in nanoseconds) used to flush internal buffers on the journal. | 20000 |
journal-compact-min-files | Integer | The minimal number of data files before we can start compacting | 10 |
journal-compact-percentage | Integer | The percentage of live data on which we consider compacting the journal | 30 |
journal-directory | String | the directory to store the journal files in | data/journal |
journal-file-size | Long | the size (in bytes) of each journal file | 10 * 1024 * 1024 (10 MiB) |
journal-max-io | Integer | the maximum number of write requests that can be in the AIO queue at any one time | 500 |
journal-min-files | Integer | how many journal files to pre-create | 2 |
journal-sync-transactional | Boolean | if true wait for transaction data to be synchronized to the journal before returning response to client | true |
journal-sync-non-transactional | Boolean | if true wait for non transaction data to be synced to the journal before returning response to client. | true |
journal-type | ASYNCIO|NIO | the type of journal to use | ASYNCIO |
jmx-management-enabled | Boolean | true means that the management API is available via JMX | true |
jmx-domain | String | the JMX domain used to registered HornetQ MBeans in the MBeanServer | org.hornetq |
log-delegate-factory-class-name | String | todo | todo |
large-messages-directory | String | the directory to store large messages | data/largemessages |
management-address | String | the name of the management address to send management messages to | jms.queue.hornetq.management |
cluster-user | String | the user used by cluster connections to communicate between the clustered nodes | HORNETQ.CLUSTER.ADMIN.USER |
cluster-password | String | the password used by cluster connections to communicate between the clustered nodes | CHANGE ME!! |
management-notification-address | String | the name of the address that consumers bind to receive management notifications | hornetq.notifications |
message-counter-enabled | Boolean | true means that message counters are enabled | false |
message-counter-max-day-history | Integer | how many days to keep message counter history | 10 |
message-counter-sample-period | Long | the sample period (in ms) to use for message counters | 10000 |
message-expiry-scan-period | Long | how often (in ms) to scan for expired messages | 30000 |
message-expiry-thread-priority | Integer | the priority of the thread expiring messages | 3 |
paging-directory | String | the directory to store paged messages in | data/paging |
persist-delivery-count-before-delivery | Boolean | true means that the delivery count is persisted before delivery. False means that this only happens after a message has been cancelled. | false |
persistence-enabled | Boolean | true means that the server will use the file based journal for persistence. | true |
persist-id-cache | Boolean | true means that id's are persisted to the journal | true |
remoting-interceptors | todo | todo | todo |
shared-store | Boolean | is this server using a shared store for failover | false |
scheduled-thread-pool-max-size | Integer | the number of threads that the main scheduled thread pool has. | 5 |
security-enabled | Boolean | true means that security is enabled | true |
security-invalidation-interval | Long | how long (in ms) to wait before invalidating the security cache | 10000 |
thread-pool-max-size | Integer | the number of threads that the main thread pool has. -1 means no limit | -1 |
async-connection-execution-enabled | Boolean | Should incoming packets on the server be handed off to a thread from the thread pool for processing or should they be handled on the remoting thread? | true |
transaction-timeout | Long | how long (in ms) before a transaction can be removed from the resource manager after create time | 60000 |
transaction-timeout-scan-period | Long | how often (in ms) to scan for timeout transactions | 1000 |
wild-card-routing-enabled | Boolean | true means that the server supports wild card routing | true |
memory-measure-interval | Long | frequency to sample JVM memory in ms (or -1 to disable memory sampling) | -1 |
memory-warning-threshold | Integer | Percentage of available memory which threshold a warning log | 25 |
connectors | Connector | a list of remoting connectors configurations to create | |
connector.name (attribute) | String | Name of the connector - mandatory | |
connector.factory-class | String | Name of the ConnectorFactory implementation - mandatory | |
connector.param | A connector configuration parameter | A key-value pair used to configure the connector. A connector can have many param | |
connector.param.key (attribute) | String | Key of a configuration parameter - mandatory | |
connector.param.value (attribute) | String | Value of a configuration parameter - mandatory | |
acceptors | Acceptor | a list of remoting acceptors to create | |
acceptor.name (attribute) | String | Name of the acceptor - optional | |
acceptor.factory-class | String | Name of the AcceptorFactory implementation - mandatory | |
acceptor.param | An acceptor configuration parameter | A key-value pair used to configure the acceptor. An acceptor can have many param | |
acceptor.param.key (attribute) | String | Key of a configuration parameter - mandatory | |
acceptor.param.value (attribute) | String | Value of a configuration parameter - mandatory | |
broadcast-groups | BroadcastGroup | a list of broadcast groups to create | |
broadcast-group.name (attribute) | String | a unique name for the broadcast group - mandatory | |
broadcast-group.local-bind-address | String | local bind address that the datagram socket is bound to | wildcard IP address chosen by the kernel |
broadcast-group.local-bind-port | Integer | local port to which the datagram socket is bound to | -1 (anonymous port) |
broadcast-group.group-address | String | multicast address to which the data will be broadcast - mandatory | |
broadcast-group.group-port | Integer | UDP port number used for broadcasting - mandatory | |
broadcast-group.broadcast-period | Long | period in milliseconds between consecutive broadcasts | 2000 (in milliseconds) |
broadcast-group.jgroups-file | String | Name of JGroups configuration file. If specified, the server uses JGroups for broadcasting. - Optional | |
broadcast-group.jgroups-channel | String | Name of JGroups Channel. If specified, the server uses the named channel for broadcasting. - Optional | |
broadcast-group.connector-ref | A pair of connector | A pair connector and optional backup connector that will be broadcasted. A broadcast-group can have multiple connector-ref | |
broadcast-group.connector-ref.connector-name (attribute) | String | Name of the live connector - mandatory | |
broadcast-group.connector-ref.backup-connector-name (attribute) | String | Name of the backup connector - optional | |
discovery-groups | DiscoveryGroup | a list of discovery groups to create | |
discovery-group.name (attribute) | String | a unique name for the discovery group - mandatory | |
discovery-group.local-bind-address | String | the discovery group will be bound only to this local address | |
discovery-group.group-address | String | Multicast IP address of the group to listen on - mandatory | |
discovery-group.group-port | Integer | UDP port of the multicast group - mandatory | |
discovery-group.refresh-timeout | Integer | Period the discovery group waits after receiving the last broadcast from a particular server before removing that servers connector pair entry from its list. | 5000 (in milliseconds) |
discovery-group.jgroups-file | String | Name of JGroups configuration file. If specified, the server uses JGroups for discovery. - Optional | |
discovery-group.jgroups-channel | String | Name of JGroups Channel. If specified, the server uses the named channel for discovery. - Optional | |
diverts | Divert | a list of diverts to use | |
divert.name (attribute) | String | a unique name for the divert - mandatory | |
divert.routing-name | String | the routing name for the divert - mandatory | |
divert.address | String | the address this divert will divert from - mandatory | |
divert.forwarding-address | String | the forwarding address for the divert - mandatory | |
divert.exclusive | Boolean | is this divert exclusive? | false |
divert.filter | String | an optional core filter expression | null |
divert.transformer-class-name | String | an optional class name of a transformer | |
queues | Queue | a list of pre configured queues to create | |
queues.name (attribute) | String | unique name of this queue | |
queues.address | String | address for this queue - mandatory | |
queues.filter | String | optional core filter expression for this queue | null |
queues.durable | Boolean | is this queue durable? | true |
bridges | Bridge | a list of bridges to create | |
bridges.name (attribute) | String | unique name for this bridge | |
bridges.queue-name | String | name of queue that this bridge consumes from - mandatory | |
bridges.forwarding-address | String | address to forward to. If omitted original address is used | null |
bridges.filter | String | optional core filter expression | null |
bridges.transformer-class-name | String | optional name of transformer class | null |
bridges.retry-interval | Long | period (in ms) between successive retries | 2000 ms |
bridges.retry-interval-multiplier | Double | multiplier to apply to successive retry intervals | 1.0 |
bridges.reconnect-attempts | Integer | maximum number of retry attempts, -1 signifies infinite | -1 |
bridges.failover-on-server-shutdown | Boolean | should failover be prompted if target server is cleanly shutdown? | false |
bridges.use-duplicate-detection | Boolean | should duplicate detection headers be inserted in forwarded messages? | true |
bridges.discovery-group-ref | String | name of discovery group used by this bridge | null |
bridges.connector-ref.connector-name (attribute) | String | name of connector to use for live connection | |
bridges.connector-ref.backup-connector-name (attribute) | String | optional name of connector to use for backup connection | null |
cluster-connections | ClusterConnection | a list of cluster connections | |
cluster-connections.name (attribute) | String | unique name for this cluster connection | |
cluster-connections.address | String | name of address this cluster connection applies to | |
cluster-connections.forward-when-no-consumers | Boolean | should messages be load balanced if there are no matching consumers on target? | false |
cluster-connections.max-hops | Integer | maximum number of hops cluster topology is propagated | 1 |
cluster-connections.retry-interval | Long | period (in ms) between successive retries | 2000 |
cluster-connections.use-duplicate-detection | Boolean | should duplicate detection headers be inserted in forwarded messages? | true |
cluster-connections.discovery-group-ref | String | name of discovery group used by this bridge | null |
cluster-connections.connector-ref.connector-name (attribute) | String | name of connector to use for live connection | |
cluster-connections.connector-ref.backup-connector-name (attribute) | String | optional name of connector to use for backup connection | null |
security-settings | SecuritySetting | a list of security settings | |
security-settings.match (attribute) | String | the string to use for matching security against an address | |
security-settings.permission | Security Permission | a permision to add to the address | |
security-settings.permission.type (attribute) | Permission Type | the type of permission | |
security-settings.permission.roles (attribute) | Roles | a comma-separated list of roles to apply the permission to | |
address-settings | AddressSetting | a list of address settings | |
address-settings.dead-letter-address | String | the address to send dead messages to | |
address-settings.max-delivery-attempts | Integer | how many times to attempt to deliver a message before sending to dead letter address | 10 |
address-settings.expiry-address | String | the address to send expired messages to | |
address-settings.redelivery-delay | Long | the time (in ms) to wait before redelivering a cancelled message. | 0 |
address-settings.last-value-queue | boolean | whether to treat the queue as a last value queue | false |
address-settings.page-size-bytes | Long | the page size (in bytes) to use for an address | 10 * 1024 * 1024 |
address-settings.max-size-bytes | Long | the maximum size (in bytes) to use in paging for an address | -1 |
address-settings.redistribution-delay | Long | how long (in ms) to wait after the last consumer is closed on a queue before redistributing messages. | -1 |
This is the configuration file used by the server side JMS service to load JMS Queues, Topics and Connection Factories.
Table 49.2. JMS Server Configuration
Element Name | Element Type | Description | Default |
---|---|---|---|
connection-factory | ConnectionFactory | a list of connection factories to create and add to JNDI |
Continued..
connection-factory.signature (attribute) | String | Type of connection factory | generic |
connection-factory.xa | Boolean | If it is a XA connection factory | false |
connection-factory.auto-group | Boolean | whether or not message grouping is automatically used | false |
connection-factory.connectors | String | A list of connectors used by the connection factory | |
connection-factory.connectors.connector-ref.connector-name (attribute) | String | Name of the connector to connect to the live server | |
connection-factory.connectors.connector-ref.backup-connector-name (attribute) | String | Name of the connector to connect to the backup server | |
connection-factory.discovery-group-ref.discovery-group-name (attribute) | String | Name of discovery group used by this connection factory | |
connection-factory.discovery-initial-wait-timeout | Long | the initial time to wait (in ms) for discovery groups to wait for broadcasts | 10000 |
connection-factory.block-on-acknowledge | Boolean | whether or not messages are acknowledged synchronously | false |
connection-factory.block-on-non-durable-send | Boolean | whether or not non-durable messages are sent synchronously | false |
connection-factory.block-on-durable-send | Boolean | whether or not durable messages are sent synchronously | true |
connection-factory.call-timeout | Long | the timeout (in ms) for remote calls | 30000 |
connection-factory.client-failure-check-period | Long | the period (in ms) after which the client will consider the connection failed after not receiving packets from the server | 5000 |
connection-factory.client-id | String | the pre-configured client ID for the connection factory | null |
connection-factory.connection-load-balancing-policy-class-name | String | the name of the load balancing class | org.hornetq.api.core.client.loadbalance.RoundRobinConnectionLoadBalancingPolicy |
connection-factory.connection-ttl | Long | the time to live (in ms) for connections | 1 * 60000 |
connection-factory.consumer-max-rate | Integer | the fastest rate a consumer may consume messages per second | -1 |
connection-factory.consumer-window-size | Integer | the window size (in bytes) for consumer flow control | 1024 * 1024 |
connection-factory.dups-ok-batch-size | Integer | the batch size (in bytes) between acknowledgements when using DUPS_OK_ACKNOWLEDGE mode | 1024 * 1024 |
connection-factory.failover-on-initial-connection | Boolean | whether or not to failover to backup on event that initial connection to live server fails | false |
connection-factory.failover-on-server-shutdown | Boolean | whether or not to failover on server shutdown | false |
connection-factory.min-large-message-size | Integer | the size (in bytes) before a message is treated as large | 100 * 1024 |
connection-factory.cache-large-message-client | Boolean | If true clients using this connection factory will hold the large message body on temporary files. | false |
connection-factory.pre-acknowledge | Boolean | whether messages are pre acknowledged by the server before sending | false |
connection-factory.producer-max-rate | Integer | the maximum rate of messages per second that can be sent | -1 |
connection-factory.producer-window-size | Integer | the window size in bytes for producers sending messages | 1024 * 1024 |
connection-factory.confirmation-window-size | Integer | the window size (in bytes) for reattachment confirmations | 1024 * 1024 |
connection-factory.reconnect-attempts | Integer | maximum number of retry attempts, -1 signifies infinite | 0 |
connection-factory.retry-interval | Long | the time (in ms) to retry a connection after failing | 2000 |
connection-factory.retry-interval-multiplier | Double | multiplier to apply to successive retry intervals | 1.0 |
connection-factory.max-retry-interval | Integer | The maximum retry interval in the case a retry-interval-multiplier has been specified | 2000 |
connection-factory.scheduled-thread-pool-max-size | Integer | the size of the scheduled thread pool | 5 |
connection-factory.thread-pool-max-size | Integer | the size of the thread pool | -1 |
connection-factory.transaction-batch-size | Integer | the batch size (in bytes) between acknowledgements when using a transactional session | 1024 * 1024 |
connection-factory.use-global-pools | Boolean | whether or not to use a global thread pool for threads | true |
queue | Queue | a queue to create and add to JNDI | |
queue.name (attribute) | String | unique name of the queue | |
queue.entry | String | context where the queue will be bound in JNDI (there can be many) | |
queue.durable | Boolean | is the queue durable? | true |
queue.filter | String | optional filter expression for the queue | |
topic | Topic | a topic to create and add to JNDI | |
topic.name (attribute) | String | unique name of the topic | |
topic.entry | String | context where the topic will be bound in JNDI (there can be many) |
By default all passwords in HornetQ server's configuration files are in plaintext form. This usually poses no security issues as those files should be well protected from unauthorized accessing. However, in some circumstances a user doesn't want to expose its passwords to more eyes than necessary.
HornetQ can be configured to use 'masked' passwords in its configuration files. A masked password is an obscure string representation of a real password. To mask a password a user will use an 'encoder'. The encoder takes in the real password and outputs the masked version. A user can then replace the real password in the configuration files with the new masked password. When HornetQ loads a masked password, it uses a suitable 'decoder' to decode it into real password.
Hornetq provides a default password encoder and decoder. Optionally users can use or implement their own encoder and decoder for masking the passwords.
The server configuration file has a property that defines the default masking behaviors over the entire file scope.
mask-password
: this boolean type property indicates if a password should be masked or not. Set it to "true"
if you want your passwords masked. The default value is "false".
The nature of the value of cluster-password is subject to the value of property 'mask-password'. If it is true the cluster-password is masked.
In the server configuration, Connectors and Acceptors sometimes needs to specify passwords. For example if a users wants to use an SSL-enabled NettyAcceptor, it can specify a key-store-password and a trust-store-password. Because Acceptors and Connectors are pluggable implementations, each transport will have different password masking needs.
When a Connector or Acceptor configuration is initialised, HornetQ will add the "mask-password" and
"password-codec" values to the Connector or Acceptors params using the keys hornetq.usemaskedpassword
and hornetq.passwordcodec
respectively. The Netty and InVM implementations will use these
as needed and any other implementations will have access to these to use if they so wish.
The following table summarizes the relations among the above-mentioned properties
Table 49.3.
mask-password | cluster-password | acceptor/connector passwords | bridge password |
---|---|---|---|
absent | plain text | plain text | plain text |
false | plain text | plain text | plain text |
true | masked | masked | masked |
Examples
Note: In the following examples if related attributed or properties are absent, it means they are not specified in the configure file.
example 1
<cluster-password>bbc</cluster-password>
This indicates the cluster password is a plaintext value ("bbc").
example 2
<mask-password>true</mask-password> <cluster-password>80cf731af62c290</cluster-password>
This indicates the cluster password is a masked value and HorentQ will use its built-in decoder to decode it. All other passwords in the configuration file, Connectors, Acceptors and Bridges, will also use masked passwords.
The JMS Bridges are configured and deployed as separate beans so they need separate configuration to control the password masking. A JMS Bridge has two password parameters in its constructor, SourcePassword and TargetPassword. It uses the following two optional properties to control their masking:
useMaskedPassword
-- If set to "true" the passwords are masked. Default is false.
passwordCodec
-- Class name and its parameters for the Decoder used to decode the masked password. Ignored if
useMaskedPassword
is false. The format of this property is a full qualified class name optionally followed by key/value pairs,
separated by semi-colons. For example:
<property name="useMaskedPassword">true</property>
<property name="passwordCodec">com.foo.FooDecoder;key=value</property>
HornetQ will load this property and initialize the class with a parameter map containing the "key"->"value" pair.
If passwordCodec
is not specified, the built-in decoder is used.
Both ra.xml and MDB activation configuration have a 'password' property that can be masked. They are controlled by the following two optional Resource Adapter properties in ra.xml:
UseMaskedPassword
-- If setting to "true" the passwords are masked. Default is false.
PasswordCodec
-- Class name and its parameters for the Decoder used to decode the masked password.
Ignored if UseMaskedPassword is false. The format of this property is a full qualified class name optionally followed by key/value pairs.
It is the same format as that for JMS Bridges. Example:
<config-property> <config-property-name>UseMaskedPassword</config-property-name> <config-property-type>boolean</config-property-type> <config-property-value>true</config-property-value> </config-property> <config-property> <config-property-name>PasswordCodec</config-property-name> <config-property-type>java.lang.String</config-property-type> <config-property-value>com.foo.ADecoder;key=helloworld</config-property-value> </config-property>
With this configuration, both passwords in ra.xml and all of its MDBs will have to be in masked form.
HornetQ's built-in security manager uses plain configuration files where the user passwords are specified in plaintext forms by default. To mask those parameters the following two properties are needed:
mask-password
-- If set to "true" all the passwords are masked. Default is false.
password-codec
-- Class name and its parameters for the Decoder used to decode the masked password.
Ignored if mask-password
is false. The format of this property is a full qualified class name optionally
followed by key/value pairs. It is the same format as that for JMS Bridges. Example:
<mask-password>true</mask-password> <password-codec>org.hornetq.utils.DefaultSensitiveStringCodec;key=hello world</password-codec>
When so configured, the HornetQ security manager will initialize a DefaultSensitiveStringCodec with the parameters "key"->"hello world", then use it to decode all the masked passwords in this configuration file.
As described in the previous sections, all password masking requires a decoder. A decoder uses an algorithm to convert a masked password into its original cleartext form in order to be used in various security operations. The algorithm used for decoding must match that for encoding. Otherwise the decoding may not be successful.
For user's convenience HornetQ provides a default built-in Decoder. However a user can if they so wish implement their own.
Whenever no decoder is specified in the configuration file, the built-in decoder is used. The class name for the built-in decoder is org.hornetq.utils.DefaultSensitiveStringCodec. It has both encoding and decoding capabilities. It uses java.crypto.Cipher utilities to encrypt (encode) a plaintext password and decrypt a mask string using same algorithm. Using this decoder/encoder is pretty straightforward. To get a mask for a password, just run the following in command line:
java org.hornetq.utils.DefaultSensitiveStringCodec "your plaintext password"
Make sure the classpath is correct. You'll get something like
Encoded password: 80cf731af62c290
Just copy "80cf731af62c290" and replace your plaintext password with it.
It is possible to use a different decoder rather than the built-in one. Simply make sure the decoder is in HornetQ's classpath and configure the server to use it as follows:
<password-codec>com.foo.SomeDecoder;key1=value1;key2=value2</password-codec>
If your decoder needs params passed to it you can do this via key/value pairs when configuring. For instance if your decoder needs say a "key-location" parameter, you can define like so:
<password-codec>com.foo.NewDecoder;key-location=/some/url/to/keyfile</password-codec>
Then configure your cluster-password like this:
<mask-password>true</mask-password> <cluster-password>masked_password</cluster-password>
When HornetQ reads the cluster-password it will initialize the NewDecoder and use it to decode "mask_password". It also process all passwords using the new defined decoder.
To use a different decoder than the built-in one, you either pick one from existing libraries or you implement it yourself.
All decoders must implement the org.hornetq.utils.SensitiveDataCodec<T>
interface:
public interface SensitiveDataCodec<T> { T decode(Object mask) throws Exception; void init(Map<String, String> params); }
This is a generic type interface but normally for a password you just need String type. So a new decoder would be defined like
public class MyNewDecoder implements SensitiveDataCodec<String> { public String decode(Object mask) throws Exception { //decode the mask into cleartext passord return "the password"; } public void init(Map<String, String> params) { //initialization done here. It is called right after the decoder has been created. } }
Last but not least, once you get your own decoder, please add it to the classpath. Otherwise HornetQ will fail to load it!