/*
* Copyright (C) 2005-2008 Jive Software. All rights reserved.
*
* 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 org.jivesoftware.openfire;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
import org.jivesoftware.openfire.session.Session;
import org.jivesoftware.util.LocaleUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.xmpp.packet.Packet;
/**
* A channel provides a mechanism to queue work units for processing. Each work unit is
* encapsulated as a ChannelMessage, and processing of each message is performed by a
* ChannelHandler.<p>
*
* As a request is handled by the system, it will travel through a sequence of channels.
* This architecture has a number of advantages:
* <ul>
* <li> Each request doesn't need to correspond to a thread. Instead, a thread pool
* in each channel processes requests from a queue.
* <li> Due to the queue at each channel, the system is much better able to respond
* to load spikes.
* </ul><p>
*
* Channels are modeled after SEDA stages. For much much more in-depth architecture information,
* refer to the <a href="http://www.cs.berkeley.edu/~mdw/proj/sandstorm/">SEDA website</a>.
*
* @author Matt Tucker
*/
public class Channel<T extends Packet> {
private static final Logger Log = LoggerFactory.getLogger(Channel.class);
private String name;
private ChannelHandler<T> channelHandler;
ThreadPoolExecutor executor;
/**
* Creates a new channel. The channel should be registered after it's created.
*
* @param name the name of the channel.
* @param channelHandler the handler for this channel.
*/
public Channel(String name, ChannelHandler<T> channelHandler) {
this.name = name;
this.channelHandler = channelHandler;
executor = new ThreadPoolExecutor(1, 8, 15, TimeUnit.SECONDS, new LinkedBlockingQueue<Runnable>());
}
/**
* Returns the name of the channel.
*
* @return the name of the channel.
*/
public String getName() {
return name;
}
/**
* Enqueus a message to be handled by this channel. After the ChannelHandler is done
* processing the message, it will be sent to the next channel. Messages with a higher
* priority will be handled first.
*
* @param packet an XMPP packet to add to the channel for processing.
*/
public void add(final T packet) {
Runnable r = new Runnable() {
@Override
public void run() {
try {
channelHandler.process(packet);
}
catch (Exception e) {
Log.error(LocaleUtils.getLocalizedString("admin.error"), e);
try {
Session session = SessionManager.getInstance().getSession(packet.getFrom());
session.close();
}
catch (Exception e1) {
Log.error(e1.getMessage(), e1);
}
}
}
};
executor.execute(r);
}
/**
* Returns true if the channel is currently running. The channel can be started and
* stopped by calling the start() and stop() methods.
*
* @return true if the channel is running.
*/
public boolean isRunning() {
return !executor.isShutdown();
}
/**
* Starts the channel, which means that worker threads will start processing messages
* from the queue. If the server isn't running, messages can still be enqueued.
*/
public void start() {
}
/**
* Stops the channel, which means that worker threads will stop processing messages from
* the queue. If the server isn't running, messages can still be enqueued.
*/
public synchronized void stop() {
executor.shutdown();
}
/**
* Returns the number of currently active worker threads in the channel. This value
* will always fall in between the min a max thread count.
*
* @return the current number of worker threads.
*/
public int getThreadCount() {
return executor.getPoolSize();
}
/**
* Returns the min number of threads the channel will use for processing messages.
* The channel will automatically de-allocate worker threads as the queue load shrinks,
* down to the defined minimum. This lets the channel consume fewer resources when load
* is low.
*
* @return the min number of threads that can be used by the channel.
*/
public int getMinThreadCount() {
return executor.getCorePoolSize();
}
/**
* Sets the min number of threads the channel will use for processing messages.
* The channel will automatically de-allocate worker threads as the queue load shrinks,
* down to the defined minimum. This lets the channel consume fewer resources when load
* is low.
*
* @param minThreadCount the min number of threads that can be used by the channel.
*/
public void setMinThreadCount(int minThreadCount) {
executor.setCorePoolSize(minThreadCount);
}
/**
* Returns the max number of threads the channel will use for processing messages. The
* channel will automatically allocate new worker threads as the queue load grows, up to the
* defined maximum. This lets the channel meet higher concurrency needs, but prevents too
* many threads from being allocated, which decreases overall system performance.
*
* @return the max number of threads that can be used by the channel.
*/
public int getMaxThreadCount() {
return executor.getMaximumPoolSize();
}
/**
* Sets the max number of threads the channel will use for processing messages. The channel
* will automatically allocate new worker threads as the queue size grows, up to the defined
* maximum. This lets the channel meet higher concurrency needs, but prevents too many threads
* from being allocated, which decreases overall system performance.
*
* @param maxThreadCount the max number of threads that can be used by the channel.
*/
public void setMaxThreadCount(int maxThreadCount) {
executor.setMaximumPoolSize(maxThreadCount);
}
/**
* Returns the current number of ChannelMessage objects waiting to be processed by
* the channel.
*
* @return the current number of elements in the processing queue.
*/
public int getQueueSize() {
return executor.getQueue().size();
}
}