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Diffstat (limited to 'java/java/broker/src/org/apache/qpid/server/queue/SynchronizedDeliveryManager.java')
| -rw-r--r-- | java/java/broker/src/org/apache/qpid/server/queue/SynchronizedDeliveryManager.java | 255 |
1 files changed, 255 insertions, 0 deletions
diff --git a/java/java/broker/src/org/apache/qpid/server/queue/SynchronizedDeliveryManager.java b/java/java/broker/src/org/apache/qpid/server/queue/SynchronizedDeliveryManager.java new file mode 100644 index 0000000000..d2e53717af --- /dev/null +++ b/java/java/broker/src/org/apache/qpid/server/queue/SynchronizedDeliveryManager.java @@ -0,0 +1,255 @@ +/* + * + * 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 org.apache.qpid.AMQException; +import org.apache.log4j.Logger; + +import java.util.LinkedList; +import java.util.Queue; +import java.util.ArrayList; +import java.util.List; +import java.util.concurrent.Executor; +import java.util.concurrent.atomic.AtomicBoolean; + +/** + * Manages delivery of messages on behalf of a queue + */ +class SynchronizedDeliveryManager implements DeliveryManager +{ + private static final Logger _log = Logger.getLogger(ConcurrentDeliveryManager.class); + + /** + * Holds any queued messages + */ + private final Queue<AMQMessage> _messages = new LinkedList<AMQMessage>(); + /** + * Ensures that only one asynchronous task is running for this manager at + * any time. + */ + private final AtomicBoolean _processing = new AtomicBoolean(); + /** + * The subscriptions on the queue to whom messages are delivered + */ + private final SubscriptionManager _subscriptions; + + /** + * An indication of the mode we are in. If this is true then messages are + * being queued up in _messages for asynchronous delivery. If it is false + * then messages can be delivered directly as they come in. + */ + private volatile boolean _queueing; + + /** + * A reference to the queue we are delivering messages for. We need this to be able + * to pass the code that handles acknowledgements a handle on the queue. + */ + private final AMQQueue _queue; + + SynchronizedDeliveryManager(SubscriptionManager subscriptions, AMQQueue queue) + { + _subscriptions = subscriptions; + _queue = queue; + } + + private synchronized boolean enqueue(AMQMessage msg) + { + if (msg.isImmediate()) + { + return false; + } + else + { + if (_queueing) + { + _messages.offer(msg); + return true; + } + else + { + return false; + } + } + } + + private synchronized void startQueueing(AMQMessage msg) + { + _queueing = true; + enqueue(msg); + } + + /** + * Determines whether there are queued messages. Sets _queueing to false if + * there are no queued messages. This needs to be atomic. + * + * @return true if there are queued messages + */ + public synchronized boolean hasQueuedMessages() + { + boolean empty = _messages.isEmpty(); + if (empty) + { + _queueing = false; + } + return !empty; + } + + public synchronized int getQueueMessageCount() + { + return _messages.size(); + } + + public synchronized List<AMQMessage> getMessages() + { + return new ArrayList<AMQMessage>(_messages); + } + + public synchronized void removeAMessageFromTop() throws AMQException + { + AMQMessage msg = poll(); + if (msg != null) + { + msg.dequeue(_queue); + } + } + + public synchronized void clearAllMessages() throws AMQException + { + AMQMessage msg = poll(); + while (msg != null) + { + msg.dequeue(_queue); + msg = poll(); + } + } + + /** + * Only one thread should ever execute this method concurrently, but + * it can do so while other threads invoke deliver(). + */ + private void processQueue() + { + try + { + boolean hasSubscribers = _subscriptions.hasActiveSubscribers(); + while (hasQueuedMessages() && hasSubscribers) + { + Subscription next = _subscriptions.nextSubscriber(peek()); + //We don't synchronize access to subscribers so need to re-check + if (next != null) + { + try + { + next.send(poll(), _queue); + } + catch (AMQException e) + { + _log.error("Unable to deliver message: " + e, e); + } + } + else + { + hasSubscribers = false; + } + } + } + finally + { + _processing.set(false); + } + } + + private synchronized AMQMessage peek() + { + return _messages.peek(); + } + + private synchronized AMQMessage poll() + { + return _messages.poll(); + } + + /** + * Requests that the delivery manager start processing the queue asynchronously + * if there is work that can be done (i.e. there are messages queued up and + * subscribers that can receive them. + * <p/> + * This should be called when subscribers are added, but only after the consume-ok + * message has been returned as message delivery may start immediately. It should also + * be called after unsuspending a client. + * <p/> + * + * @param executor the executor on which the delivery should take place + */ + public void processAsync(Executor executor) + { + if (hasQueuedMessages() && _subscriptions.hasActiveSubscribers()) + { + //are we already running? if so, don't re-run + if (_processing.compareAndSet(false, true)) + { + executor.execute(new Runner()); + } + } + } + + /** + * Handles message delivery. The delivery manager is always in one of two modes; + * it is either queueing messages for asynchronous delivery or delivering + * directly. + * + * @param name the name of the entity on whose behalf we are delivering the message + * @param msg the message to deliver + * @throws NoConsumersException if there are no active subscribers to deliver + * the message to + */ + public void deliver(String name, AMQMessage msg) throws FailedDequeueException + { + // first check whether we are queueing, and enqueue if we are + if (!enqueue(msg)) + { + synchronized(this) + { + // not queueing so deliver message to 'next' subscriber + Subscription s = _subscriptions.nextSubscriber(msg); + if (s == null) + { + // no subscribers yet so enter 'queueing' mode and queue this message + startQueueing(msg); + } + else + { + s.send(msg, _queue); + msg.setDeliveredToConsumer(); + } + } + } + + } + + private class Runner implements Runnable + { + public void run() + { + processQueue(); + } + } +} |