org.jboss.netty.channel.socket.oio.OioClientSocketChannelFactory Maven / Gradle / Ivy

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The Netty project is an effort to provide an asynchronous event-driven network application framework and tools for rapid development of maintainable high performance and high scalability protocol servers and clients. In other words, Netty is a NIO client server framework which enables quick and easy development of network applications such as protocol servers and clients. It greatly simplifies and streamlines network programming such as TCP and UDP socket server.

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/*
 * Copyright 2012 The Netty Project
 *
 * The Netty Project 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.jboss.netty.channel.socket.oio;

import java.util.concurrent.Executor;
import java.util.concurrent.Executors;
import java.util.concurrent.RejectedExecutionException;

import org.jboss.netty.channel.Channel;
import org.jboss.netty.channel.ChannelPipeline;
import org.jboss.netty.channel.group.ChannelGroup;
import org.jboss.netty.channel.socket.ClientSocketChannelFactory;
import org.jboss.netty.channel.socket.SocketChannel;
import org.jboss.netty.util.internal.ExecutorUtil;

/**
 * A {@link ClientSocketChannelFactory} which creates a client-side blocking
 * I/O based {@link SocketChannel}.  It utilizes the good old blocking I/O API
 * which is known to yield better throughput and latency when there are
 * relatively small number of connections to serve.
 *
 * How threads work
 * 
 * There is only one type of threads in {@link OioClientSocketChannelFactory};
 * worker threads.
 *
 * 
Worker threads
 * 
 * Each connected {@link Channel} has a dedicated worker thread, just like a
 * traditional blocking I/O thread model.
 *
 * 
Life cycle of threads and graceful shutdown
 * 
 * Worker threads are acquired from the {@link Executor} which was specified
 * when a {@link OioClientSocketChannelFactory} was created (i.e. {@code workerExecutor}.)
 * Therefore, you should make sure the specified {@link Executor} is able to
 * lend the sufficient number of threads.
 * 

 * Worker threads are acquired lazily, and then released when there's nothing
 * left to process.  All the related resources are also released when the
 * worker threads are released.  Therefore, to shut down a service gracefully,
 * you should do the following:
 *
 * 

 * close all channels created by the factory usually using
 *     {@link ChannelGroup#close()}, and
 * call {@link #releaseExternalResources()}.
 * 
 *
 * Please make sure not to shut down the executor until all channels are
 * closed.  Otherwise, you will end up with a {@link RejectedExecutionException}
 * and the related resources might not be released properly.
 *
 * Limitation
 * 
 * A {@link SocketChannel} created by this factory does not support asynchronous
 * operations.  Any I/O requests such as {@code "connect"} and {@code "write"}
 * will be performed in a blocking manner.
 *
 * @apiviz.landmark
 */
public class OioClientSocketChannelFactory implements ClientSocketChannelFactory {

    private final Executor workerExecutor;
    final OioClientSocketPipelineSink sink;

    /**
     * Creates a new instance with a {@link Executors#newCachedThreadPool()} as worker executor.
     *
     * See {@link #OioClientSocketChannelFactory(Executor)}
     */
    public OioClientSocketChannelFactory() {
        this(Executors.newCachedThreadPool());
    }

    /**
     * Creates a new instance.
     *
     * @param workerExecutor
     *        the {@link Executor} which will execute the I/O worker threads
     */
    public OioClientSocketChannelFactory(Executor workerExecutor) {
        if (workerExecutor == null) {
            throw new NullPointerException("workerExecutor");
        }
        this.workerExecutor = workerExecutor;
        sink = new OioClientSocketPipelineSink(workerExecutor);
    }

    public SocketChannel newChannel(ChannelPipeline pipeline) {
        return new OioClientSocketChannel(this, pipeline, sink);
    }

    public void releaseExternalResources() {
        ExecutorUtil.terminate(workerExecutor);
    }
}