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).
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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.conf.AttributeType;
import org.jgroups.stack.Protocol;
import org.jgroups.util.Util;
import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
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://issues.redhat.com/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 {
@Property(description="Loop back multicast messages")
boolean loopback=true;
@ManagedAttribute(description="The member to which all multicasts are forwarded")
protected volatile Address next;
@ManagedAttribute(description="The current view")
protected volatile View view;
@ManagedAttribute(type=AttributeType.SCALAR)
protected int msgs_forwarded;
@ManagedAttribute(type=AttributeType.SCALAR)
protected int msgs_sent;
protected TP transport;
public void resetStats() {
super.resetStats();
msgs_forwarded=msgs_sent=0;
}
public void init() throws Exception {
transport=getTransport();
}
public Object down(final Event evt) {
switch(evt.getType()) {
case Event.VIEW_CHANGE:
handleView(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't been received yet, use the normal transport
return down_prot.down(msg);
if(loopback) {
if(msg.getSrc() == null && local_addr != null)
msg.setSrc(local_addr);
if(log.isTraceEnabled())
log.trace("%s: looping back message %s", local_addr, msg);
transport.loopback(msg, true);
}
// 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, true).setDest(next)
.putHeader(getId(), new DaisyHeader(local_addr));
msgs_sent++;
if(log.isTraceEnabled())
log.trace("%s: forwarding multicast message %s (hdrs: %s) to %s", local_addr, msg, msg.getHeaders(), next);
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, unless next is the original sender
if(log.isTraceEnabled())
log.trace("%s: received message from %s with original sender=%s", local_addr, msg.getSrc(), hdr.getOriginalSender());
if(next != null && !next.equals(hdr.getOriginalSender())) {
Message copy=msg.copy(true, true).setSrc(null) // so TP will set src to local_addr
.setDest(next);
msgs_forwarded++;
if(log.isTraceEnabled())
log.trace("%s: forwarding message to %s", local_addr, next);
down_prot.down(copy);
}
// 2. Pass up
msg.setDest(null).setSrc(hdr.getOriginalSender());
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("%s: received message from %s with ttl=%d", local_addr, msg.getSrc(), ttl);
if(--ttl > 0) {
Message copy=msg.copy(true, true)
.setDest(next).putHeader(getId(), new DaisyHeader(ttl));
msgs_forwarded++;
if(log.isTraceEnabled())
log.trace("%s: forwarding message to %s with ttl=%d", local_addr, next, ttl);
down_prot.down(copy);
}
// 2. Pass up
msg.setDest(null);
}
}
if(!batch.isEmpty())
up_prot.up(batch);
}*/
protected void handleView(View view) {
this.view=view;
Address tmp=Util.pickNext(view.getMembers(), local_addr);
if(tmp != null && !tmp.equals(local_addr)) {
next=tmp;
log.debug("%s: next=%s", local_addr, next);
}
else
next=null;
}
public static class DaisyHeader extends Header {
protected Address original_sender;
public DaisyHeader() {
}
public DaisyHeader(Address original_sender) {
this.original_sender=original_sender;
}
public short getMagicId() {return 69;}
public Address getOriginalSender() {return original_sender;}
public DaisyHeader setOriginalSender(Address s) {this.original_sender=s; return null;}
public Supplier create() {return DaisyHeader::new;}
@Override public int serializedSize() {return Util.size(original_sender);}
@Override public void writeTo(DataOutput out) throws IOException {Util.writeAddress(original_sender, out);}
@Override public void readFrom(DataInput in) throws IOException, ClassNotFoundException {
original_sender=Util.readAddress(in);
}
public String toString() {return "original sender=" + original_sender;}
}
}