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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.handler.execution;

import org.jboss.netty.channel.Channel;
import org.jboss.netty.channel.ChannelEvent;
import org.jboss.netty.channel.ChannelFuture;
import org.jboss.netty.channel.ChannelFutureListener;
import org.jboss.netty.util.ObjectSizeEstimator;

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

/**
 * {@link Executor} which should be used for downstream {@link ChannelEvent}'s. This implementation
 * will take care of preserve the order of the events in a {@link Channel}.  If you don't need to
 * preserve the order just use one of the {@link Executor} implementations provided by the static
 * methods of {@link Executors}.
 * 

 * 

 * For more informations about how the order is preserved see {@link OrderedMemoryAwareThreadPoolExecutor}
 */
public final class OrderedDownstreamThreadPoolExecutor extends OrderedMemoryAwareThreadPoolExecutor {

    /**
     * Creates a new instance.
     *
     * @param corePoolSize          the maximum number of active threads
     */
    public OrderedDownstreamThreadPoolExecutor(int corePoolSize) {
        super(corePoolSize, 0L, 0L);
    }

    /**
     * Creates a new instance.
     *
     * @param corePoolSize          the maximum number of active threads
     * @param keepAliveTime         the amount of time for an inactive thread to shut itself down
     * @param unit                  the {@link TimeUnit} of {@code keepAliveTime}
     */
    public OrderedDownstreamThreadPoolExecutor(
            int corePoolSize, long keepAliveTime, TimeUnit unit) {
        super(corePoolSize, 0L, 0L, keepAliveTime, unit);
    }

    /**
     * Creates a new instance.
     *
     * @param corePoolSize          the maximum number of active threads
     * @param keepAliveTime         the amount of time for an inactive thread to shut itself down
     * @param unit                  the {@link TimeUnit} of {@code keepAliveTime}
     * @param threadFactory         the {@link ThreadFactory} of this pool
     */
    public OrderedDownstreamThreadPoolExecutor(
            int corePoolSize, long keepAliveTime, TimeUnit unit, ThreadFactory threadFactory) {
        super(corePoolSize, 0L, 0L,
                keepAliveTime, unit, threadFactory);
    }

    /**
     * Return {@code null}
     */
    @Override
    public ObjectSizeEstimator getObjectSizeEstimator() {
        return null;
    }

    /**
     * Throws {@link UnsupportedOperationException} as there is not support for limit the memory
     * size in this implementation
     */
    @Override
    public void setObjectSizeEstimator(ObjectSizeEstimator objectSizeEstimator) {
        throw new UnsupportedOperationException("Not supported by this implementation");
    }

    /**
     * Returns {@code 0L}
     */
    @Override
    public long getMaxChannelMemorySize() {
        return 0L;
    }

    /**
     * Throws {@link UnsupportedOperationException} as there is not support for limit the memory
     * size in this implementation
     */
    @Override
    public void setMaxChannelMemorySize(long maxChannelMemorySize) {
        throw new UnsupportedOperationException("Not supported by this implementation");
    }

    /**
     * Returns {@code 0L}
     */
    @Override
    public long getMaxTotalMemorySize() {
        return 0L;
    }

    /**
     * Throws {@link UnsupportedOperationException} as there is not support for limit the memory
     * size in this implementation
     */
    @Override
    @Deprecated
    public void setMaxTotalMemorySize(long maxTotalMemorySize) {
        throw new UnsupportedOperationException("Not supported by this implementation");
    }

    /**
     * Return {@code false} as we not need to cound the memory in this implementation
     */
    @Override
    protected boolean shouldCount(Runnable task) {
        return false;
    }

    @Override
    public void execute(Runnable command) {

        // check if the Runnable was of an unsupported type
        if (command instanceof ChannelUpstreamEventRunnable) {
            throw new RejectedExecutionException("command must be enclosed with an downstream event.");
        }
        doExecute(command);
    }

    @Override
    protected Executor getChildExecutor(ChannelEvent e) {
        final Object key = getChildExecutorKey(e);
        Executor executor = childExecutors.get(key);
        if (executor == null) {
            executor = new ChildExecutor();
            Executor oldExecutor = childExecutors.putIfAbsent(key, executor);
            if (oldExecutor != null) {
                executor = oldExecutor;
            } else {
                // register a listener so that the ChildExecutor will get removed once the channel was closed
                e.getChannel().getCloseFuture().addListener(new ChannelFutureListener() {

                    public void operationComplete(ChannelFuture future) throws Exception {
                        removeChildExecutor(key);
                    }
                });
            }
        }

        return executor;
    }
}