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    1   /*
    2    * Copyright 2009 Red Hat, Inc.
    3    *
    4    * Red Hat licenses this file to you under the Apache License, version 2.0
    5    * (the "License"); you may not use this file except in compliance with the
    6    * 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.RejectedExecutionException;
    20
    21  import org.jboss.netty.channel.Channel;
    22  import org.jboss.netty.channel.ChannelPipeline;
    23  import org.jboss.netty.channel.group.ChannelGroup;
    24  import org.jboss.netty.channel.socket.DatagramChannel;
    25  import org.jboss.netty.channel.socket.DatagramChannelFactory;
    26  import org.jboss.netty.util.internal.ExecutorUtil;
    27
    28  /**
    29   * A {@link DatagramChannelFactory} which creates a blocking I/O based
    30   * {@link DatagramChannel}.  It utilizes the good old blocking I/O API which
    31   * has support for multicast.
    32   *
    33   * <h3>How threads work</h3>
    34   * <p>
    35   * There is only one type of threads in {@link OioDatagramChannelFactory};
    36   * worker threads.
    37   *
    38   * <h4>Worker threads</h4>
    39   * <p>
    40   * Each {@link Channel} has a dedicated worker thread, just like a
    41   * traditional blocking I/O thread model.
    42   *
    43   * <h3>Life cycle of threads and graceful shutdown</h3>
    44   * <p>
    45   * Worker threads are acquired from the {@link Executor} which was specified
    46   * when a {@link OioDatagramChannelFactory} was created (i.e. {@code workerExecutor}.)
    47   * Therefore, you should make sure the specified {@link Executor} is able to
    48   * lend the sufficient number of threads.
    49   * <p>
    50   * Worker threads are acquired lazily, and then released when there's nothing
    51   * left to process.  All the related resources are also released when the
    52   * worker threads are released.  Therefore, to shut down a service gracefully,
    53   * you should do the following:
    54   *
    55   * <ol>
    56   * <li>close all channels created by the factory usually using
    57   *     {@link ChannelGroup#close()}, and</li>
    58   * <li>call {@link #releaseExternalResources()}.</li>
    59   * </ol>
    60   *
    61   * Please make sure not to shut down the executor until all channels are
    62   * closed.  Otherwise, you will end up with a {@link RejectedExecutionException}
    63   * and the related resources might not be released properly.
    64   *
    65   * <h3>Limitation</h3>
    66   * <p>
    67   * A {@link DatagramChannel} created by this factory does not support asynchronous
    68   * operations.  Any I/O requests such as {@code "write"} will be performed in a
    69   * blocking manner.
    70   *
    71   * @author <a href="http://www.jboss.org/netty/">The Netty Project</a>
    72   * @author <a href="http://gleamynode.net/">Trustin Lee</a>
    73   *
    74   * @version $Rev: 2080 $, $Date: 2010-01-26 18:04:19 +0900 (Tue, 26 Jan 2010) $
    75   *
    76   * @apiviz.landmark
    77   */
    78  public class OioDatagramChannelFactory implements DatagramChannelFactory {
    79
    80      private final Executor workerExecutor;
    81      final OioDatagramPipelineSink sink;
    82
    83      /**
    84       * Creates a new instance.
    85       *
    86       * @param workerExecutor
    87       *        the {@link Executor} which will execute the I/O worker threads
    88       */
    89      public OioDatagramChannelFactory(Executor workerExecutor) {
    90          if (workerExecutor == null) {
    91              throw new NullPointerException("workerExecutor");
    92          }
    93          this.workerExecutor = workerExecutor;
    94          sink = new OioDatagramPipelineSink(workerExecutor);
    95      }
    96
    97      public DatagramChannel newChannel(ChannelPipeline pipeline) {
    98          return new OioDatagramChannel(this, pipeline, sink);
    99      }
    100
    101     public void releaseExternalResources() {
    102         ExecutorUtil.terminate(workerExecutor);
    103     }
    104 }