org.jgroups.protocols

Class DAISYCHAIN

java.lang.Object

org.jgroups.stack.Protocol

org.jgroups.protocols.DAISYCHAIN

public class DAISYCHAIN
extends Protocol

Implementation of daisy chaining. Multicast messages are sent to our neighbor, which sends them to its neighbor etc. A TTL restricts the number of times a message is forwarded. The advantage of daisy chaining is that - for point-to-point transports such as TCP - we can avoid the N-1 issue: when A sends a multicast message to 10 members, it needs to send it 9 times. With daisy chaining, it sends it 1 time, and in the next round, can already send another message. This leads to much better throughput, see the ref in the JIRA.

Should be inserted just above MERGE2, in TCP based configurations. JIRA: https://jira.jboss.org/browse/JGRP-1021

Since:

2.11

Author:

Bela Ban

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	DAISYCHAIN.DaisyHeader

Field Summary

Fields

Modifier and Type	Field and Description
protected Executor	default_pool
protected boolean	forward
protected BlockingQueue<Message>	forward_queue
protected Address	local_addr
int	msgs_forwarded
int	msgs_sent
protected Address	next
protected Executor	oob_pool
protected boolean	running
protected BlockingQueue<Message>	send_queue
protected int	view_size

Fields inherited from class org.jgroups.stack.Protocol

down_prot, ergonomics, id, log, name, stack, stats, up_prot

Constructor Summary

Constructors

Constructor and Description
DAISYCHAIN()

Method Summary

Methods

Modifier and Type	Method and Description
Object	down(Event evt) An event is to be sent down the stack.
int	getElementsInForwardQueue()
int	getElementsInSendQueue()
protected void	handleView(View view)
void	init() Called after instance has been created (null constructor) and before protocol is started.
protected Object	processQueues()
void	start() This method is called on a Channel.connect(String).
void	stop() This method is called on a Channel.disconnect().
Object	up(Event evt) An event was received from the layer below.

Methods inherited from class org.jgroups.stack.Protocol

destroy, dumpStats, enableStats, getConfigurableObjects, getDownProtocol, getId, getLevel, getName, getProtocolStack, getSocketFactory, getThreadFactory, getTransport, getUpProtocol, getValue, isErgonomics, printStats, providedDownServices, providedUpServices, requiredDownServices, requiredUpServices, resetStatistics, resetStats, setDownProtocol, setErgonomics, setId, setLevel, setProtocolStack, setSocketFactory, setUpProtocol, setValue, setValues, statsEnabled

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

local_addr

protected Address local_addr

next

protected Address next

view_size

protected int view_size

default_pool

protected Executor default_pool

oob_pool

protected Executor oob_pool

send_queue

protected BlockingQueue<Message> send_queue

forward_queue

protected BlockingQueue<Message> forward_queue

forward

protected volatile boolean forward

running

protected volatile boolean running

msgs_forwarded

public int msgs_forwarded

msgs_sent

public int msgs_sent

Constructor Detail

DAISYCHAIN

public DAISYCHAIN()

Method Detail

getElementsInForwardQueue

public int getElementsInForwardQueue()

getElementsInSendQueue

public int getElementsInSendQueue()

init

public void init()
          throws Exception

Description copied from class: Protocol

Called after instance has been created (null constructor) and before protocol is started. Properties are already set. Other protocols are not yet connected and events cannot yet be sent.

Overrides:

init in class Protocol

Throws:

Exception - Thrown if protocol cannot be initialized successfully. This will cause the ProtocolStack to fail, so the channel constructor will throw an exception

start

public void start()
           throws Exception

Description copied from class: Protocol

This method is called on a Channel.connect(String). Starts work. Protocols are connected and queues are ready to receive events. Will be called from bottom to top. This call will replace the START and START_OK events.

Overrides:

start in class Protocol

Throws:

Exception - Thrown if protocol cannot be started successfully. This will cause the ProtocolStack to fail, so Channel.connect(String) will throw an exception

stop

public void stop()

Description copied from class: Protocol

This method is called on a Channel.disconnect(). Stops work (e.g. by closing multicast socket). Will be called from top to bottom. This means that at the time of the method invocation the neighbor protocol below is still working. This method will replace the STOP, STOP_OK, CLEANUP and CLEANUP_OK events. The ProtocolStack guarantees that when this method is called all messages in the down queue will have been flushed

Overrides:

stop in class Protocol

down

public Object down(Event evt)

Description copied from class: Protocol

An event is to be sent down the stack. The layer may want to examine its type and perform some action on it, depending on the event's type. If the event is a message MSG, then the layer may need to add a header to it (or do nothing at all) before sending it down the stack using down_prot.down(). In case of a GET_ADDRESS event (which tries to retrieve the stack's address from one of the bottom layers), the layer may need to send a new response event back up the stack using up_prot.up().

Overrides:

down in class Protocol

up

public Object up(Event evt)

Description copied from class: Protocol

An event was received from the layer below. Usually the current layer will want to examine the event type and - depending on its type - perform some computation (e.g. removing headers from a MSG event type, or updating the internal membership list when receiving a VIEW_CHANGE event). Finally the event is either a) discarded, or b) an event is sent down the stack using down_prot.down() or c) the event (or another event) is sent up the stack using up_prot.up().

Overrides:

up in class Protocol

processQueues

protected Object processQueues()

handleView

protected void handleView(View view)