Preparation & Scenario

Download WildFly 8

First we should download WildFly 8 from the website:

http://www.jboss.org/jbossas/downloads/

The version I downloaded is JBoss AS 7.1.0.CR1b, please don't use the version prior to this one, or you will meet this bug when running in clustering mode:

https://issues.jboss.org/browse/AS7-2738

After download finished, I got the zip file:

jboss-as-7.1.0.CR1b.zip

Note: The name of your archive will differ slightly due to version naming conventions.
Then I unzipped the package to master and try to make a test run:

unzip jboss-as-7.1.0.CR1b.zip
cd jboss-as-7.1.0.CR1b/bin
./domain.sh

If all is well, we should see WildFly successfully start in domain mode:

jboss-as-7.1.0.CR1b/bin$ ./domain.sh
=========================================================================

  JBoss Bootstrap Environment

  JBOSS_HOME: /Users/weli/Downloads/jboss-as-7.1.0.CR1b

  JAVA: /Library/Java/Home/bin/java

  JAVA_OPTS: -Xms64m -Xmx512m -XX:MaxPermSize=256m -Djava.net.preferIPv4Stack=true -Dorg.jboss.resolver.warning=true -Dsun.rmi.dgc.client.gcInterval=3600000 -Dsun.rmi.dgc.server.gcInterval=3600000 -Djboss.modules.system.pkgs=org.jboss.byteman -Djava.awt.headless=true

=========================================================================
...

[Server:server-two] 16:59:55,870 INFO  [org.jboss.as] (Controller Boot Thread) JBoss AS 7.1.0.CR1b "Flux Capacitor" started in 2499ms - Started 148 of 214 services (64 services are passive or on-demand)

Now exit master and let's repeat the same steps on slave. Once we get WildFly 8 running on both master and slave, we can move on to the next step.

Domain Configuration

vi domain/configuration/host.xml

<interfaces>
    <interface name="management">
        <inet-address value="${jboss.bind.address.management:127.0.0.1}"/>
    </interface>
    <interface name="public">
       <inet-address value="${jboss.bind.address:127.0.0.1}"/>
    </interface>
    <interface name="unsecured">       
       <inet-address value="127.0.0.1" />    
    </interface>
</interfaces>

<interfaces>
    <interface name="management"
        <inet-address value="${jboss.bind.address.management:10.211.55.7}"/>
    </interface>
    <interface name="public">
       <inet-address value="${jboss.bind.address:10.211.55.7}"/>
    </interface>    
    <interface name="unsecured">
       <inet-address value="10.211.55.7" />    
    </interface>
</interfaces> 

mv domain/configuration/domain.xml domain/configuration/domain.xml.move

vi domain/configuration/host.xml

<host name="master" xmlns="urn:jboss:domain:1.1">

<host name="slave" xmlns="urn:jboss:domain:1.1">

<domain-controller>
   <remote host="10.211.55.7" port="9999"/>
</domain-controller>

<interfaces>
    <interface name="management">
        <inet-address value="${jboss.bind.address.management:10.211.55.2}"/>
    </interface>
    <interface name="public">
       <inet-address value="${jboss.bind.address:10.211.55.2}"/>
    </interface>
    <interface name="unsecured">       
       <inet-address value="10.211.55.2" />    
    </interface>
</interfaces>

[Host Controller] 20:31:24,575 ERROR [org.jboss.remoting.remote] (Remoting "endpoint" read-1) JBREM000200: Remote connection failed: javax.security.sasl.SaslException: Authentication failed: all available authentication mechanisms failed
[Host Controller] 20:31:24,579 WARN  [org.jboss.as.host.controller] (Controller Boot Thread) JBAS010900: Could not connect to remote domain controller 10.211.55.7:9999
[Host Controller] 20:31:24,582 ERROR [org.jboss.as.host.controller] (Controller Boot Thread) JBAS010901: Could not connect to master. Aborting. Error was: java.lang.IllegalStateException: JBAS010942: Unable to connect due to authentication failure.

./add-user.sh

Enter the details of the new user to add.
Realm (ManagementRealm) :
Username : admin
Password : 123123
Re-enter Password : 123123
The username 'admin' is easy to guess
Are you sure you want to add user 'admin' yes/no? yes
About to add user 'admin' for realm 'ManagementRealm'
Is this correct yes/no? yes
Added user 'admin' to file '/home/weli/projs/jboss-as-7.1.0.CR1b/standalone/configuration/mgmt-users.properties'
Added user 'admin' to file '/home/weli/projs/jboss-as-7.1.0.CR1b/domain/configuration/mgmt-users.properties'

./add-user.sh

Enter the details of the new user to add.
Realm (ManagementRealm) :
Username : slave
Password : 123123
Re-enter Password : 123123
About to add user 'slave' for realm 'ManagementRealm'
Is this correct yes/no? yes
Added user 'slave' to file '/home/weli/projs/jboss-as-7.1.0.CR1b/standalone/configuration/mgmt-users.properties'
Added user 'slave' to file '/home/weli/projs/jboss-as-7.1.0.CR1b/domain/configuration/mgmt-users.properties'

./add-user.sh   What type of user do you wish to add?
 a) Management User (mgmt-users.properties)
 b) Application User (application-user.properties)
 (a):

<security-realms>
   <security-realm name="ManagementRealm">
       <server-identities>
           <secret value="MTIzMTIz="/>
       </server-identities>
       <authentication>
           <properties path="mgmt-users.properties" relative-to="jboss.domain.config.dir"/>
       </authentication>
   </security-realm>
</security-realms>

<domain-controller>
   <remote host="10.211.55.7" port="9999" security-realm="ManagementRealm"/>
</domain-controller>

[Host Controller] 21:30:52,042 INFO  [org.jboss.as.domain] (management-handler-threads - 1) JBAS010918: Registered remote slave host slave

Deployment

Now we can deploy a demo project into the domain. I have created a simple project located at:

https://github.com/liweinan/cluster-demo

We can use the git command to fetch a copy of the demo:

git clone git://github.com/liweinan/cluster-demo.git

In this demo project we have a very simple web application. In web.xml we've enabled session replication by adding following entry:

<distributable/>

And it contains a jsp page called put.jsp which will put the current time into a session attribute called 'current.time':

<%
    session.setAttribute("current.time", new java.util.Date());
%>

Then we can obtain this value using get.jsp:

The time is <%= session.getAttribute("current.time") %>

It's an extremely simple project but it could help us to test the cluster later: we will access put.jsp from the cluster and check that the request is distributed to master, then we disconnect master and access get.jsp. We should see the request is forwarded to slave but the 'current.time' value is held by session replication. We'll cover this in more detail later.

Let's go back to this demo project. Now we need to create a war from it. In the project directory, run the following command to get the war:

mvn package

It will generate cluster-demo.war. Then we need to deploy the war into domain. First we should access the http management console on master (because master is acting as domain controller):

http://10.211.55.7:9990

It will prompt you for an account name and password.  We can use the 'admin' account we added a short while ago. After logging in we see the 'Server Instances' window. By default there are three servers listed, which are:

• server-one

• server-two

• server-three

We can see that server-one and server-two have the status 'running' and that they belong to main-server-group; server-three has the status 'idle', and belongs to other-server-group.

All these servers and server groups are set in domain.xml on master as7. What we are interested in is the 'other-server-group' in domain.xml:

<server-group name="other-server-group" profile="ha">
   <jvm name="default">
       <heap size="64m" max-size="512m"/>
   </jvm>
   <socket-binding-group ref="ha-sockets"/>
</server-group>

We can see that this server-group is using the 'ha' profile, which then uses the 'ha-sockets' socket binding group. It enables all the modules we need to establish the cluster later (including infinispan, jgroup and mod_cluster modules). So we will deploy our demo project into a server that belongs to 'other-server-group', so 'server-three' is our choice.

<server-group name="other-server-group" profile="full-ha">

Let's go back to the domain controller's management console:

http://10.211.55.7:9990

Now server-three is not running, so let's click on 'server-three' and then click the 'start' button at the bottom right of the server list. Wait a moment and server-three should start.

Now we should also enable 'server-three' on slave: from the top of the menu list on the left-hand side of the page, we can see that we are currently managing master. Click on the list, select 'slave', then choose 'server-three'.  We are now on the host management page for slave.

Then repeat these steps on master to start 'server-three' on slave.

After server-three on both master and slave are started, we will add our cluster-demo.war for deployment. Click on the 'Manage Deployments' link at the bottom of left menu list.

We should ensure that server-three is started on both master and slave.

After the enter 'Manage Deployments' page, click 'Add Content' at the top right-hand corner. Then choose the cluster-demo.war, and follow the instructions to add it into our content repository.

Now we can see cluster-demo.war is added. Next we click the 'Add to Groups' button and add the war to 'other-server-group' and then click 'save'.

After a few seconds, the management console will say that the project is deployed into 'other-server-group'.：

Please note that we have two hosts participating in this server group, so the project should be deployed in both master and slave now - that's the power of domain management.

Now let's verify this, trying to access cluster-demo from both master and slave:

http://10.211.55.7:8330/cluster-demo/

http://10.211.55.2:8330/cluster-demo/

Now that we have finished the project deployment and seen the usage of the domain controller, we will then use these two hosts to establish a cluster

<server name="server-three" group="other-server-group" auto-start="false">
    <!-- server-three avoids port conflicts by incrementing the ports in
         the default socket-group declared in the server-group -->
    <socket-bindings port-offset="250"/>
</server>

Now we quit the WildFly process on both master and slave. We have some work left to do on the host.xml configurations. Open host.xml on master, and make some modifications to the servers section:

<server name="server-three" group="other-server-group" auto-start="false">
    <!-- server-three avoids port conflicts by incrementing the ports in
         the default socket-group declared in the server-group -->
    <socket-bindings port-offset="250"/>
</server>

to:

<server name="server-three" group="other-server-group" auto-start="true">
    <!-- server-three avoids port conflicts by incrementing the ports in
         the default socket-group declared in the server-group -->
    <socket-bindings port-offset="250"/>
</server>

We've set auto-start to true so we don't need to enable it in the management console each time WildFly restarts. Now open slave's host.xml, and modify the server-three section:

<server name="server-three-slave" group="other-server-group" auto-start="true">
    <!-- server-three avoids port conflicts by incrementing the ports in
         the default socket-group declared in the server-group -->
    <socket-bindings port-offset="250"/>
</server>

Besides setting auto-start to true, we've also renamed the 'server-three' to 'server-three-slave'. We need to do this because mod_cluster will fail to register the hosts with same name in a single server group, due to a name conflict.

After finishing the above configuration, let's restart the two as7 hosts and examine the cluster configuration.

Cluster Configuration

We will use mod_cluster + apache httpd on master as our cluster controller here. WildFly 8 has been configured to support mod_cluster out of box, so it's the easiest way.

First we need to ensure that httpd is installed:

sudo yum install httpd

And then we need to download newer version of mod_cluster from its website:

http://www.jboss.org/mod_cluster/downloads

The version I downloaded is:

http://downloads.jboss.org/mod_cluster/1.1.3.Final/mod_cluster-1.1.3.Final-linux2-x86-so.tar.gz

Then we extract it into:

/etc/httpd/modules

Then we edit httpd.conf:

sudo vi /etc/httpd/conf/httpd.conf

We should add the modules:

LoadModule slotmem_module modules/mod_slotmem.so
LoadModule manager_module modules/mod_manager.so
LoadModule proxy_cluster_module modules/mod_proxy_cluster.so
LoadModule advertise_module modules/mod_advertise.so

Note that we should comment out the proxy_balancer_module:

#LoadModule proxy_balancer_module modules/mod_proxy_balancer.so

This is because it will otherwise conflict with the cluster module. And then we need to make httpd listen on the public address so we can perform the testing. Because we installed httpd on master host, we know its IP address:

Listen 10.211.55.7:80

Then we do the necessary configuration at the bottom of httpd.conf:

# This Listen port is for the mod_cluster-manager, where you can see the status of mod_cluster.
# Port 10001 is not a reserved port, so this prevents problems with SELinux.
Listen 10.211.55.7:10001
# This directive only applies to Red Hat Enterprise Linux. It prevents the temmporary
# files from being written to /etc/httpd/logs/ which is not an appropriate location.
MemManagerFile /var/cache/httpd

<VirtualHost 10.211.55.7:10001>

  <Directory />
    Order deny,allow
    Deny from all
    Allow from 10.211.55.
  </Directory>


  # This directive allows you to view mod_cluster status at URL http://10.211.55.4:10001/mod_cluster-manager
  <Location /mod_cluster-manager>
   SetHandler mod_cluster-manager
   Order deny,allow
   Deny from all
   Allow from 10.211.55.
  </Location>

  KeepAliveTimeout 60
  MaxKeepAliveRequests 0

  ManagerBalancerName other-server-group
  AdvertiseFrequency 5

</VirtualHost>

http://docs.jboss.org/mod_cluster/1.2.0/html/Quick_Start_Guide.html

Testing

All being well, we can start the httpd service:

service httpd start

Now we access the cluster:

http://10.211.55.7/cluster-demo/put.jsp

We should see from the WildFly log that the request is distributed to one of the hosts (master or slave). In this instance, the request is sent to master:

[Server:server-three] 16:06:22,256 INFO  [stdout] (http-10.211.55.7-10.211.55.7-8330-4) Putting date now

Now I disconnect master by using the management interface. Select 'runtime' and the server 'master' in the upper corners.

Select 'server-three' and click the stop button.  The active icon should change.

Killing the server by using system commands will cause the Host-Controller to restart the instance immediately!

After a few seconds, access the cluster:

http://10.211.55.7/cluster-demo/get.jsp

Now the request should be served by slave, which should see borne out in slave's log:

[Server:server-three-slave] 16:08:29,860 INFO  [stdout] (http-10.211.55.2-10.211.55.2-8330-1) Getting date now

And from get.jsp we should see that the time returned is the same gathered by 'put.jsp'. Thus it's proven that the session has correctly replicated to slave.

Now we restart master and should see that the host is registered back to the cluster.

Special Thanks

Wolf-Dieter Fink has contributed the updated add-user.sh usages and configs in host.xml from 7.1.0.Final.
Jean-Frederic Clere provided the mod_cluster 1.2.0 usage.
Misty Stanley-Jones has given a lot of suggestions and helps to make this document readable.