1 /*
2 * Copyright 2012 The Netty Project
3 *
4 * The Netty Project licenses this file to you under the Apache License,
5 * version 2.0 (the "License"); you may not use this file except in compliance
6 * with the License. You may obtain a copy of the License at:
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
12 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
13 * License for the specific language governing permissions and limitations
14 * under the License.
15 */
16 package org.jboss.netty.channel.socket.oio;
17
18 import java.util.concurrent.Executor;
19 import java.util.concurrent.Executors;
20 import java.util.concurrent.RejectedExecutionException;
21
22 import org.jboss.netty.channel.Channel;
23 import org.jboss.netty.channel.ChannelPipeline;
24 import org.jboss.netty.channel.group.ChannelGroup;
25 import org.jboss.netty.channel.socket.ClientSocketChannelFactory;
26 import org.jboss.netty.channel.socket.SocketChannel;
27 import org.jboss.netty.util.internal.ExecutorUtil;
28
29 /**
30 * A {@link ClientSocketChannelFactory} which creates a client-side blocking
31 * I/O based {@link SocketChannel}. It utilizes the good old blocking I/O API
32 * which is known to yield better throughput and latency when there are
33 * relatively small number of connections to serve.
34 *
35 * <h3>How threads work</h3>
36 * <p>
37 * There is only one type of threads in {@link OioClientSocketChannelFactory};
38 * worker threads.
39 *
40 * <h4>Worker threads</h4>
41 * <p>
42 * Each connected {@link Channel} has a dedicated worker thread, just like a
43 * traditional blocking I/O thread model.
44 *
45 * <h3>Life cycle of threads and graceful shutdown</h3>
46 * <p>
47 * Worker threads are acquired from the {@link Executor} which was specified
48 * when a {@link OioClientSocketChannelFactory} was created (i.e. {@code workerExecutor}.)
49 * Therefore, you should make sure the specified {@link Executor} is able to
50 * lend the sufficient number of threads.
51 * <p>
52 * Worker threads are acquired lazily, and then released when there's nothing
53 * left to process. All the related resources are also released when the
54 * worker threads are released. Therefore, to shut down a service gracefully,
55 * you should do the following:
56 *
57 * <ol>
58 * <li>close all channels created by the factory usually using
59 * {@link ChannelGroup#close()}, and</li>
60 * <li>call {@link #releaseExternalResources()}.</li>
61 * </ol>
62 *
63 * Please make sure not to shut down the executor until all channels are
64 * closed. Otherwise, you will end up with a {@link RejectedExecutionException}
65 * and the related resources might not be released properly.
66 *
67 * <h3>Limitation</h3>
68 * <p>
69 * A {@link SocketChannel} created by this factory does not support asynchronous
70 * operations. Any I/O requests such as {@code "connect"} and {@code "write"}
71 * will be performed in a blocking manner.
72 *
73 * @apiviz.landmark
74 */
75 public class OioClientSocketChannelFactory implements ClientSocketChannelFactory {
76
77 private final Executor workerExecutor;
78 final OioClientSocketPipelineSink sink;
79
80 /**
81 * Creates a new instance with a {@link Executors#newCachedThreadPool()} as worker executor.
82 *
83 * See {@link #OioClientSocketChannelFactory(Executor)}
84 */
85 public OioClientSocketChannelFactory() {
86 this(Executors.newCachedThreadPool());
87 }
88
89 /**
90 * Creates a new instance.
91 *
92 * @param workerExecutor
93 * the {@link Executor} which will execute the I/O worker threads
94 */
95 public OioClientSocketChannelFactory(Executor workerExecutor) {
96 if (workerExecutor == null) {
97 throw new NullPointerException("workerExecutor");
98 }
99 this.workerExecutor = workerExecutor;
100 sink = new OioClientSocketPipelineSink(workerExecutor);
101 }
102
103 public SocketChannel newChannel(ChannelPipeline pipeline) {
104 return new OioClientSocketChannel(this, pipeline, sink);
105 }
106
107 public void releaseExternalResources() {
108 ExecutorUtil.terminate(workerExecutor);
109 }
110 }