/*
* Copyright 2014 Cisco Systems, Inc.
*
* Licensed 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 com.cisco.oss.foundation.message;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;
/**
* MessageDispatcher contains thread pool to process messages in parallel;
* For each received message it check whether it dispatchable, if so it dispatch it to the thread-pool;
* otherwise it put it on waiting list and will try to dispatch it when a thread from the thread-pool became free.
* MessageDispatcher is thread-safe.
* @author yglass
*
*/
class LockMessageDispatcher extends AbstractMessageDispatcher {
//private static final Logger LOGGER = LoggerFactory.getLogger(LockMessageDispatcher.class);
private Lock waitingReadLock;
private Lock waitingWriteLock;
LockMessageDispatcher(ConcurrentMessageHandler concurrentMessageHandler){
super(concurrentMessageHandler);
ReadWriteLock waitingReadWriteLock = new ReentrantReadWriteLock();
waitingReadLock = waitingReadWriteLock.readLock();
waitingWriteLock = waitingReadWriteLock.writeLock();
}
/**
* A RejectedExecutionException could be thrown in case there too many requests.
*/
protected boolean checkAndDispatchEvent(Message message, boolean alreadyOnWaitingList){
boolean isDispatchable = false;
// Try to dispatch the event
synchronized (this){
isDispatchable = getConcurrentMessageHandler().isDispatchable(message);
if (isDispatchable){
getConcurrentMessageHandler().onDispatchMessage(message);
}
}
if (isDispatchable){
dispatchMessage(message);
return true;
}
if (alreadyOnWaitingList){
return false;
}
// In case the event can't be dispatch now, add it to the waiting list
waitingWriteLock.lock();
try {
// If the current key is on work OR the working threads are full - put the message on waiting list (FIFO)
getWaitingList().add(message);
}
finally {
waitingWriteLock.unlock();
}
return false;
}
protected void pushNextEvent() {
// Push next message from waiting list
Message nextEvent = null;
boolean dispatchedEvent = false;
waitingReadLock.lock();
try {
for (Message event : getWaitingList()){
dispatchedEvent = checkAndDispatchEvent(event, true);
if (dispatchedEvent){
nextEvent = event;
break;
}
}
}
finally {
waitingReadLock.unlock();
}
if (dispatchedEvent){
waitingWriteLock.lock();
try {
getWaitingList().remove(nextEvent);
}
finally {
waitingWriteLock.unlock();
}
}
}
}