/*
* JBoss, Home of Professional Open Source
* Copyright 2005, JBoss Inc., and individual contributors as indicated
* by the @authors tag. See the copyright.txt in the distribution for a
* full listing of individual contributors.
*
* This is free software; you can redistribute it and/or modify it
* under the terms of the GNU Lesser General Public License as
* published by the Free Software Foundation; either version 2.1 of
* the License, or (at your option) any later version.
*
* This software is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this software; if not, write to the Free
* Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
* 02110-1301 USA, or see the FSF site: http://www.fsf.org.
*/
package org.jboss.messaging.core.local;
import java.util.ArrayList;
import java.util.Iterator;
import org.jboss.logging.Logger;
import org.jboss.messaging.core.Delivery;
import org.jboss.messaging.core.DeliveryObserver;
import org.jboss.messaging.core.Receiver;
import org.jboss.messaging.core.Router;
import org.jboss.messaging.core.SimpleDelivery;
import org.jboss.messaging.core.message.MessageReference;
import org.jboss.messaging.core.tx.Transaction;
/**
*
* The router will always first try the next receiver in the list to the one it tried last time.
* This gives a more balanced distribution than the FirstReceiverPointToPointRouter and is better
* suited when batching messages to consumers since we will end up with messages interleaved amongst
* consumers rather than in contiguous blocks.
*
* @author <a href="mailto:tim.fox@jboss.com">Tim Fox</a>
* @author <a href="mailto:ovidiu@jboss.org">Ovidiu Feodorov</a>
* @version <tt>$Revision: 1 $</tt>
* $Id: $
*/
public class RoundRobinPointToPointRouter implements Router
{
// Constants ------------------------------------------------------------------------------------
private static final Logger log = Logger.getLogger(RoundRobinPointToPointRouter.class);
// Static ---------------------------------------------------------------------------------------
// Attributes -----------------------------------------------------------------------------------
private boolean trace = log.isTraceEnabled();
// it's important that we're actually using an ArrayList for fast array access
private ArrayList receivers;
private int target;
private volatile boolean makeCopy;
private ArrayList receiversCopy;
// Constructors ---------------------------------------------------------------------------------
public RoundRobinPointToPointRouter()
{
receivers = new ArrayList();
target = 0;
makeCopy = true;
}
// Router implementation ------------------------------------------------------------------------
public Delivery handle(DeliveryObserver observer, MessageReference ref, Transaction tx)
{
if (makeCopy)
{
synchronized (this)
{
// We make a copy of the receivers to avoid a race condition:
// http://jira.jboss.org/jira/browse/JBMESSAGING-505
// Note that we do not make a copy every time - only when the receivers have changed
receiversCopy = new ArrayList(receivers);
if (target >= receiversCopy.size())
{
target = 0;
}
makeCopy = false;
}
}
if (receiversCopy.isEmpty())
{
return null;
}
Delivery del = null;
boolean selectorRejected = false;
int initial = target;
while (true)
{
Receiver r = (Receiver)receiversCopy.get(target);
try
{
Delivery d = r.handle(observer, ref, tx);
if (trace) { log.trace("receiver " + r + " handled " + ref + " and returned " + d); }
if (d != null)
{
if (d.isSelectorAccepted())
{
// deliver to the first receiver that accepts
del = d;
incTarget();
break;
}
else
{
selectorRejected = true;
}
}
}
catch(Throwable t)
{
// broken receiver - log the exception and ignore it
log.error("The receiver " + r + " is broken", t);
}
incTarget();
// if we've tried them all then we break
if (target == initial)
{
break;
}
}
if (del == null && selectorRejected)
{
del = new SimpleDelivery(null, null, true, false);
}
return del;
}
public synchronized boolean add(Receiver r)
{
if (receivers.contains(r))
{
return false;
}
receivers.add(r);
makeCopy = true;
return true;
}
public synchronized boolean remove(Receiver r)
{
boolean removed = receivers.remove(r);
if (removed)
{
makeCopy = true;
}
return removed;
}
public synchronized void clear()
{
receivers.clear();
makeCopy = true;
}
public synchronized boolean contains(Receiver r)
{
return receivers.contains(r);
}
public synchronized Iterator iterator()
{
return receivers.iterator();
}
public synchronized int getNumberOfReceivers()
{
return receivers.size();
}
// Public ---------------------------------------------------------------------------------------
// Package protected ----------------------------------------------------------------------------
// Protected ------------------------------------------------------------------------------------
// Private --------------------------------------------------------------------------------------
private void incTarget()
{
target++;
if (target == receiversCopy.size())
{
target = 0;
}
}
// Inner classes --------------------------------------------------------------------------------
}