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.io.IOException;
import java.util.concurrent.Executor;
import java.util.function.Supplier;
/**
* 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;
/* --------------------------------------------- Fields ------------------------------------------------------ */
protected volatile Address local_addr, next;
protected int view_size=0;
protected Executor default_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().getThreadPool();
}
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.VIEW_CHANGE:
handleView(evt.getArg());
break;
case Event.TMP_VIEW:
view_size=((View)evt.getArg()).size();
break;
case Event.SET_LOCAL_ADDRESS:
local_addr=evt.getArg();
break;
}
return down_prot.down(evt);
}
public Object down(Message msg) {
if(msg.getDest() != null)
return down_prot.down(msg); // only process multicast messages
if(next == null) // view hasn'<> been received yet, use the normal transport
return down_prot.down(msg);
// 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);
default_pool.execute(() -> up_prot.up(msg));
}
return down_prot.down(copy);
}
public Object up(Message msg) {
DaisyHeader hdr=msg.getHeader(getId());
if(hdr == null)
return up_prot.up(msg);
// 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(copy);
}
// 2. Pass up
msg.setDest(null);
return up_prot.up(msg);
}
public void up(MessageBatch batch) {
for(Message msg: batch) {
DaisyHeader hdr=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(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 getMagicId() {return 69;}
public short getTTL() {return ttl;}
public void setTTL(short ttl) {
this.ttl=ttl;
}
public Supplier create() {return DaisyHeader::new;}
@Override
public int serializedSize() {
return Global.SHORT_SIZE;
}
@Override
public void writeTo(DataOutput out) throws IOException {
out.writeShort(ttl);
}
@Override
public void readFrom(DataInput in) throws IOException {
ttl=in.readShort();
}
public String toString() {
return "ttl=" + ttl;
}
}
}