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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 org.jboss.netty.channel.Channel;
  import org.jboss.netty.channel.ChannelPipeline;
  import org.jboss.netty.channel.ChannelSink;
  import org.jboss.netty.channel.group.ChannelGroup;
  import org.jboss.netty.channel.socket.ServerSocketChannel;
  import org.jboss.netty.channel.socket.ServerSocketChannelFactory;
  import org.jboss.netty.util.ThreadNameDeterminer;
  import org.jboss.netty.util.internal.ExecutorUtil;
  
  import java.util.concurrent.Executor;
  import java.util.concurrent.Executors;
  import java.util.concurrent.RejectedExecutionException;
  
  /**
   * A {@link ServerSocketChannelFactory} which creates a server-side blocking
   * I/O based {@link ServerSocketChannel}.  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.
   *
   * <h3>How threads work</h3>
   * <p>
   * There are two types of threads in a {@link OioServerSocketChannelFactory};
   * one is boss thread and the other is worker thread.
   *
   * <h4>Boss threads</h4>
   * <p>
   * Each bound {@link ServerSocketChannel} has its own boss thread.
   * For example, if you opened two server ports such as 80 and 443, you will
   * have two boss threads.  A boss thread accepts incoming connections until
   * the port is unbound.  Once a connection is accepted successfully, the boss
   * thread passes the accepted {@link Channel} to one of the worker
   * threads that the {@link OioServerSocketChannelFactory} manages.
   *
   * <h4>Worker threads</h4>
   * <p>
   * Each connected {@link Channel} has a dedicated worker thread, just like a
   * traditional blocking I/O thread model.
   *
   * <h3>Life cycle of threads and graceful shutdown</h3>
   * <p>
   * All threads are acquired from the {@link Executor}s which were specified
   * when a {@link OioServerSocketChannelFactory} was created.  Boss threads are
   * acquired from the {@code bossExecutor}, and worker threads are acquired from
   * the {@code workerExecutor}.  Therefore, you should make sure the specified
   * {@link Executor}s are able to lend the sufficient number of threads.
   * <p>
   * Both boss and worker threads are acquired lazily, and then released when
   * there's nothing left to process.  All the related resources are also
   * released when the boss and worker threads are released.  Therefore, to shut
   * down a service gracefully, you should do the following:
   *
   * <ol>
   * <li>unbind all channels created by the factory,
   * <li>close all child channels accepted by the unbound channels,
   *     (these two steps so far is usually done using {@link ChannelGroup#close()})</li>
   * <li>call {@link #releaseExternalResources()}.</li>
   * </ol>
   *
   * 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.
   *
   * <h3>Limitation</h3>
   * <p>
   * A {@link ServerSocketChannel} created by this factory and its child channels
   * do not support asynchronous operations.  Any I/O requests such as
   * {@code "write"} will be performed in a blocking manner.
   *
   * @apiviz.landmark
   */
  public class OioServerSocketChannelFactory implements ServerSocketChannelFactory {
  
      final Executor bossExecutor;
      private final Executor workerExecutor;
      private final ChannelSink sink;
      private boolean shutdownExecutor;
  
      /**
       * Create a new {@link OioServerSocketChannelFactory} with a {@link Executors#newCachedThreadPool()}
       * for the boss and worker executor.
       *
       * See {@link #OioServerSocketChannelFactory(Executor, Executor)}
      */
     public OioServerSocketChannelFactory() {
         this(Executors.newCachedThreadPool(), Executors.newCachedThreadPool());
         shutdownExecutor = true;
     }
 
     /**
      * Creates a new instance.
      *
      * @param bossExecutor
      *        the {@link Executor} which will execute the boss threads
      * @param workerExecutor
      *        the {@link Executor} which will execute the I/O worker threads
      */
     public OioServerSocketChannelFactory(
             Executor bossExecutor, Executor workerExecutor) {
         this(bossExecutor, workerExecutor, null);
     }
 
     /**
      * Creates a new instance.
      *
      * @param bossExecutor
      *        the {@link Executor} which will execute the boss threads
      * @param workerExecutor
      *        the {@link Executor} which will execute the I/O worker threads
      * @param determiner
      *        the {@link ThreadNameDeterminer} to set the thread names.
      */
     public OioServerSocketChannelFactory(Executor bossExecutor, Executor workerExecutor,
                                          ThreadNameDeterminer determiner) {
         if (bossExecutor == null) {
             throw new NullPointerException("bossExecutor");
         }
         if (workerExecutor == null) {
             throw new NullPointerException("workerExecutor");
         }
         this.bossExecutor = bossExecutor;
         this.workerExecutor = workerExecutor;
         sink = new OioServerSocketPipelineSink(workerExecutor, determiner);
     }
 
     public ServerSocketChannel newChannel(ChannelPipeline pipeline) {
         return new OioServerSocketChannel(this, pipeline, sink);
     }
 
     public void shutdown() {
         if (shutdownExecutor) {
             ExecutorUtil.shutdownNow(bossExecutor);
             ExecutorUtil.shutdownNow(workerExecutor);
         }
     }
 
     public void releaseExternalResources() {
         ExecutorUtil.shutdownNow(bossExecutor);
         ExecutorUtil.shutdownNow(workerExecutor);
     }
 }