org.jgroups.protocols.DAISYCHAIN Maven / Gradle / Ivy
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This artifact provides a single jar that contains all classes required to use remote EJB and JMS, including
all dependencies. It is intended for use by those not using maven, maven users should just import the EJB and
JMS BOM's instead (shaded JAR's cause lots of problems with maven, as it is very easy to inadvertently end up
with different versions on classes on the class path).
package org.jgroups.protocols;
import org.jgroups.*;
import org.jgroups.annotations.Experimental;
import org.jgroups.annotations.MBean;
import org.jgroups.annotations.ManagedAttribute;
import org.jgroups.annotations.Property;
import org.jgroups.stack.Protocol;
import org.jgroups.util.MessageBatch;
import org.jgroups.util.Util;
import java.io.DataInput;
import java.io.DataOutput;
import java.util.concurrent.Executor;
/**
* 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 MERGE3, in TCP based configurations.
* JIRA: https://jira.jboss.org/browse/JGRP-1021
* @author Bela Ban
* @since 2.11
*/
@Experimental
@MBean(description="Protocol just above the transport which disseminates multicasts via daisy chaining")
public class DAISYCHAIN extends Protocol {
/* ----------------------------------------- Properties -------------------------------------------------- */
@Property(description="Loop back multicast messages")
boolean loopback=true;
@Property(description="The number of messages in the forward queue. This queue is used to host messages that " +
"need to be forwarded by us on behalf of our neighbor",deprecatedMessage="not used anymore")
int forward_queue_size=10000;
@Property(description="The number of messages in the send queue. This queue is used to host messages that need " +
"to be sent",deprecatedMessage="not used anymore")
int send_queue_size=10000;
/* --------------------------------------------- Fields ------------------------------------------------------ */
protected volatile Address local_addr, next;
protected int view_size=0;
protected Executor default_pool=null;
protected Executor oob_pool=null;
protected volatile boolean running=true;
@ManagedAttribute
public int msgs_forwarded=0;
@ManagedAttribute
public int msgs_sent=0;
public void resetStats() {
super.resetStats();
msgs_forwarded=msgs_sent=0;
}
public void init() throws Exception {
default_pool=getTransport().getDefaultThreadPool();
oob_pool=getTransport().getOOBThreadPool();
}
public void start() throws Exception {
super.start();
running=true;
}
public void stop() {
super.stop();
running=false;
}
public Object down(final Event evt) {
switch(evt.getType()) {
case Event.MSG:
final Message msg=(Message)evt.getArg();
if(msg.getDest() != null)
break; // only process multicast messages
if(next == null) // view hasn't been received yet, use the normal transport
break;
// we need to copy the message, as we cannot do a msg.setSrc(next): the next retransmission
// would use 'next' as destination !
Message copy=msg.copy(true);
short hdr_ttl=(short)(loopback? view_size -1 : view_size);
DaisyHeader hdr=new DaisyHeader(hdr_ttl);
copy.setDest(next);
copy.putHeader(getId(), hdr);
msgs_sent++;
if(loopback) {
if(log.isTraceEnabled()) log.trace(new StringBuilder("looping back message ").append(msg));
if(msg.getSrc() == null)
msg.setSrc(local_addr);
Executor pool=msg.isFlagSet(Message.Flag.OOB)? oob_pool : default_pool;
pool.execute(new Runnable() {
public void run() {
up_prot.up(evt);
}
});
}
return down_prot.down(new Event(Event.MSG, copy));
case Event.VIEW_CHANGE:
handleView((View)evt.getArg());
break;
case Event.TMP_VIEW:
view_size=((View)evt.getArg()).size();
break;
case Event.SET_LOCAL_ADDRESS:
local_addr=(Address)evt.getArg();
break;
}
return down_prot.down(evt);
}
public Object up(Event evt) {
switch(evt.getType()) {
case Event.MSG:
Message msg=(Message)evt.getArg();
DaisyHeader hdr=(DaisyHeader)msg.getHeader(getId());
if(hdr == null)
break;
// 1. forward the message to the next in line if ttl > 0
short ttl=hdr.getTTL();
if(log.isTraceEnabled())
log.trace(local_addr + ": received message from " + msg.getSrc() + " with ttl=" + ttl);
if(--ttl > 0) {
Message copy=msg.copy(true);
copy.setDest(next);
copy.putHeader(getId(), new DaisyHeader(ttl));
msgs_forwarded++;
if(log.isTraceEnabled())
log.trace(local_addr + ": forwarding message to " + next + " with ttl=" + ttl);
down_prot.down(new Event(Event.MSG, copy));
}
// 2. Pass up
msg.setDest(null);
break;
}
return up_prot.up(evt);
}
public void up(MessageBatch batch) {
for(Message msg: batch) {
DaisyHeader hdr=(DaisyHeader)msg.getHeader(getId());
if(hdr != null) {
// 1. forward the message to the next in line if ttl > 0
short ttl=hdr.getTTL();
if(log.isTraceEnabled())
log.trace(local_addr + ": received message from " + msg.getSrc() + " with ttl=" + ttl);
if(--ttl > 0) {
Message copy=msg.copy(true);
copy.setDest(next);
copy.putHeader(getId(), new DaisyHeader(ttl));
msgs_forwarded++;
if(log.isTraceEnabled())
log.trace(local_addr + ": forwarding message to " + next + " with ttl=" + ttl);
down_prot.down(new Event(Event.MSG, copy));
}
// 2. Pass up
msg.setDest(null);
}
}
if(!batch.isEmpty())
up_prot.up(batch);
}
protected void handleView(View view) {
view_size=view.size();
Address tmp=Util.pickNext(view.getMembers(), local_addr);
if(tmp != null && !tmp.equals(local_addr)) {
next=tmp;
if(log.isDebugEnabled())
log.debug("next=" + next);
}
}
public static class DaisyHeader extends Header {
private short ttl;
public DaisyHeader() {
}
public DaisyHeader(short ttl) {
this.ttl=ttl;
}
public short getTTL() {return ttl;}
public void setTTL(short ttl) {
this.ttl=ttl;
}
public int size() {
return Global.SHORT_SIZE;
}
public void writeTo(DataOutput out) throws Exception {
out.writeShort(ttl);
}
public void readFrom(DataInput in) throws Exception {
ttl=in.readShort();
}
public String toString() {
return "ttl=" + ttl;
}
}
}