/*
*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*
*/
package org.apache.qpid.server.queue;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.atomic.AtomicReference;
import org.apache.qpid.server.message.ServerMessage;
import org.apache.qpid.server.txn.AutoCommitTransaction;
import org.apache.qpid.server.txn.ServerTransaction;
public class ConflationQueueList extends SimpleQueueEntryList
{
private final String _conflationKey;
private final ConcurrentHashMap<Object, AtomicReference<QueueEntry>> _latestValuesMap =
new ConcurrentHashMap<Object, AtomicReference<QueueEntry>>();
public ConflationQueueList(AMQQueue queue, String conflationKey)
{
super(queue);
_conflationKey = conflationKey;
}
public String getConflationKey()
{
return _conflationKey;
}
@Override
protected ConflationQueueEntry createQueueEntry(ServerMessage message)
{
return new ConflationQueueEntry(this, message);
}
@Override
public QueueEntry add(final ServerMessage message)
{
ConflationQueueEntry entry = (ConflationQueueEntry) (super.add(message));
AtomicReference<QueueEntry> latestValueReference = null;
Object value = message.getMessageHeader().getHeader(_conflationKey);
if(value != null)
{
latestValueReference = _latestValuesMap.get(value);
if(latestValueReference == null)
{
_latestValuesMap.putIfAbsent(value, new AtomicReference<QueueEntry>(entry));
latestValueReference = _latestValuesMap.get(value);
}
QueueEntry oldEntry;
do
{
oldEntry = latestValueReference.get();
}
while(oldEntry.compareTo(entry) < 0 && !latestValueReference.compareAndSet(oldEntry, entry));
if(oldEntry.compareTo(entry) < 0)
{
// We replaced some other entry to become the newest value
if(oldEntry.acquire())
{
discardEntry(oldEntry);
}
}
else if (oldEntry.compareTo(entry) > 0)
{
// A newer entry came along
discardEntry(entry);
}
}
entry.setLatestValueReference(latestValueReference);
return entry;
}
private void discardEntry(final QueueEntry entry)
{
if(entry.acquire())
{
ServerTransaction txn = new AutoCommitTransaction(getQueue().getVirtualHost().getTransactionLog());
txn.dequeue(entry.getQueue(),entry.getMessage(),
new ServerTransaction.Action()
{
public void postCommit()
{
entry.discard();
}
public void onRollback()
{
}
});
}
}
private final class ConflationQueueEntry extends QueueEntryImpl
{
private AtomicReference<QueueEntry> _latestValueReference;
public ConflationQueueEntry(SimpleQueueEntryList queueEntryList, ServerMessage message)
{
super(queueEntryList, message);
}
public void release()
{
super.release();
if(_latestValueReference != null)
{
if(_latestValueReference.get() != this)
{
discardEntry(this);
}
}
}
public void setLatestValueReference(final AtomicReference<QueueEntry> latestValueReference)
{
_latestValueReference = latestValueReference;
}
}
static class Factory implements QueueEntryListFactory
{
private final String _conflationKey;
Factory(String conflationKey)
{
_conflationKey = conflationKey;
}
public QueueEntryList createQueueEntryList(AMQQueue queue)
{
return new ConflationQueueList(queue, _conflationKey);
}
}
}