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Java example source code file (ThreadPerChannelEventLoopGroup.java)

This example Java source code file (ThreadPerChannelEventLoopGroup.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

channelexception, channelfuture, channelpromise, deprecated, eventloop, executor, futurelistener, nullpointerexception, object, override, threading, threadperchanneleventloopgroup, threads, throwable, timeunit, unusedparameters, util

The ThreadPerChannelEventLoopGroup.java Java example source code

/*
 * 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 io.netty.channel;


import io.netty.util.concurrent.AbstractEventExecutorGroup;
import io.netty.util.concurrent.DefaultPromise;
import io.netty.util.concurrent.EventExecutor;
import io.netty.util.concurrent.Future;
import io.netty.util.concurrent.FutureListener;
import io.netty.util.concurrent.GlobalEventExecutor;
import io.netty.util.concurrent.Promise;
import io.netty.util.concurrent.ThreadPerTaskExecutor;
import io.netty.util.internal.EmptyArrays;
import io.netty.util.internal.PlatformDependent;
import io.netty.util.internal.ReadOnlyIterator;
import io.netty.util.internal.ThrowableUtil;

import java.util.Collections;
import java.util.Iterator;
import java.util.Queue;
import java.util.Set;
import java.util.concurrent.ConcurrentLinkedQueue;
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;

/**
 * An {@link EventLoopGroup} that creates one {@link EventLoop} per {@link Channel}.
 */
public class ThreadPerChannelEventLoopGroup extends AbstractEventExecutorGroup implements EventLoopGroup {

    private final Object[] childArgs;
    private final int maxChannels;
    final Executor executor;
    final Set<EventLoop> activeChildren =
            Collections.newSetFromMap(PlatformDependent.<EventLoop, Boolean>newConcurrentHashMap());
    final Queue<EventLoop> idleChildren = new ConcurrentLinkedQueue();
    private final ChannelException tooManyChannels;

    private volatile boolean shuttingDown;
    private final Promise<?> terminationFuture = new DefaultPromise(GlobalEventExecutor.INSTANCE);
    private final FutureListener<Object> childTerminationListener = new FutureListener() {
        @Override
        public void operationComplete(Future<Object> future) throws Exception {
            // Inefficient, but works.
            if (isTerminated()) {
                terminationFuture.trySuccess(null);
            }
        }
    };

    /**
     * Create a new {@link ThreadPerChannelEventLoopGroup} with no limit in place.
     */
    protected ThreadPerChannelEventLoopGroup() {
        this(0);
    }

    /**
     * Create a new {@link ThreadPerChannelEventLoopGroup}.
     *
     * @param maxChannels       the maximum number of channels to handle with this instance. Once you try to register
     *                          a new {@link Channel} and the maximum is exceed it will throw an
     *                          {@link ChannelException}. on the {@link #register(Channel)} and
     *                          {@link #register(ChannelPromise)} method.
     *                          Use {@code 0} to use no limit
     */
    protected ThreadPerChannelEventLoopGroup(int maxChannels) {
        this(maxChannels, Executors.defaultThreadFactory());
    }

    /**
     * Create a new {@link ThreadPerChannelEventLoopGroup}.
     *
     * @param maxChannels       the maximum number of channels to handle with this instance. Once you try to register
     *                          a new {@link Channel} and the maximum is exceed it will throw an
     *                          {@link ChannelException} on the {@link #register(Channel)} and
     *                          {@link #register(ChannelPromise)} method.
     *                          Use {@code 0} to use no limit
     * @param threadFactory     the {@link ThreadFactory} used to create new {@link Thread} instances that handle the
     *                          registered {@link Channel}s
     * @param args              arguments which will passed to each {@link #newChild(Object...)} call.
     */
    protected ThreadPerChannelEventLoopGroup(int maxChannels, ThreadFactory threadFactory, Object... args) {
        this(maxChannels, new ThreadPerTaskExecutor(threadFactory), args);
    }

    /**
     * Create a new {@link ThreadPerChannelEventLoopGroup}.
     *
     * @param maxChannels       the maximum number of channels to handle with this instance. Once you try to register
     *                          a new {@link Channel} and the maximum is exceed it will throw an
     *                          {@link ChannelException} on the {@link #register(Channel)} and
     *                          {@link #register(ChannelPromise)} method.
     *                          Use {@code 0} to use no limit
     * @param executor          the {@link Executor} used to create new {@link Thread} instances that handle the
     *                          registered {@link Channel}s
     * @param args              arguments which will passed to each {@link #newChild(Object...)} call.
     */
    protected ThreadPerChannelEventLoopGroup(int maxChannels, Executor executor, Object... args) {
        if (maxChannels < 0) {
            throw new IllegalArgumentException(String.format(
                    "maxChannels: %d (expected: >= 0)", maxChannels));
        }
        if (executor == null) {
            throw new NullPointerException("executor");
        }

        if (args == null) {
            childArgs = EmptyArrays.EMPTY_OBJECTS;
        } else {
            childArgs = args.clone();
        }

        this.maxChannels = maxChannels;
        this.executor = executor;

        tooManyChannels = ThrowableUtil.unknownStackTrace(
                new ChannelException("too many channels (max: " + maxChannels + ')'),
                ThreadPerChannelEventLoopGroup.class, "nextChild()");
    }

    /**
     * Creates a new {@link EventLoop}.  The default implementation creates a new {@link ThreadPerChannelEventLoop}.
     */
    protected EventLoop newChild(@SuppressWarnings("UnusedParameters") Object... args) throws Exception {
        return new ThreadPerChannelEventLoop(this);
    }

    @Override
    public Iterator<EventExecutor> iterator() {
        return new ReadOnlyIterator<EventExecutor>(activeChildren.iterator());
    }

    @Override
    public EventLoop next() {
        throw new UnsupportedOperationException();
    }

    @Override
    public Future<?> shutdownGracefully(long quietPeriod, long timeout, TimeUnit unit) {
        shuttingDown = true;

        for (EventLoop l: activeChildren) {
            l.shutdownGracefully(quietPeriod, timeout, unit);
        }
        for (EventLoop l: idleChildren) {
            l.shutdownGracefully(quietPeriod, timeout, unit);
        }

        // Notify the future if there was no children.
        if (isTerminated()) {
            terminationFuture.trySuccess(null);
        }

        return terminationFuture();
    }

    @Override
    public Future<?> terminationFuture() {
        return terminationFuture;
    }

    @Override
    @Deprecated
    public void shutdown() {
        shuttingDown = true;

        for (EventLoop l: activeChildren) {
            l.shutdown();
        }
        for (EventLoop l: idleChildren) {
            l.shutdown();
        }

        // Notify the future if there was no children.
        if (isTerminated()) {
            terminationFuture.trySuccess(null);
        }
    }

    @Override
    public boolean isShuttingDown() {
        for (EventLoop l: activeChildren) {
            if (!l.isShuttingDown()) {
                return false;
            }
        }
        for (EventLoop l: idleChildren) {
            if (!l.isShuttingDown()) {
                return false;
            }
        }
        return true;
    }

    @Override
    public boolean isShutdown() {
        for (EventLoop l: activeChildren) {
            if (!l.isShutdown()) {
                return false;
            }
        }
        for (EventLoop l: idleChildren) {
            if (!l.isShutdown()) {
                return false;
            }
        }
        return true;
    }

    @Override
    public boolean isTerminated() {
        for (EventLoop l: activeChildren) {
            if (!l.isTerminated()) {
                return false;
            }
        }
        for (EventLoop l: idleChildren) {
            if (!l.isTerminated()) {
                return false;
            }
        }
        return true;
    }

    @Override
    public boolean awaitTermination(long timeout, TimeUnit unit)
            throws InterruptedException {
        long deadline = System.nanoTime() + unit.toNanos(timeout);
        for (EventLoop l: activeChildren) {
            for (;;) {
                long timeLeft = deadline - System.nanoTime();
                if (timeLeft <= 0) {
                    return isTerminated();
                }
                if (l.awaitTermination(timeLeft, TimeUnit.NANOSECONDS)) {
                    break;
                }
            }
        }
        for (EventLoop l: idleChildren) {
            for (;;) {
                long timeLeft = deadline - System.nanoTime();
                if (timeLeft <= 0) {
                    return isTerminated();
                }
                if (l.awaitTermination(timeLeft, TimeUnit.NANOSECONDS)) {
                    break;
                }
            }
        }
        return isTerminated();
    }

    @Override
    public ChannelFuture register(Channel channel) {
        if (channel == null) {
            throw new NullPointerException("channel");
        }
        try {
            EventLoop l = nextChild();
            return l.register(new DefaultChannelPromise(channel, l));
        } catch (Throwable t) {
            return new FailedChannelFuture(channel, GlobalEventExecutor.INSTANCE, t);
        }
    }

    @Override
    public ChannelFuture register(ChannelPromise promise) {
        try {
            return nextChild().register(promise);
        } catch (Throwable t) {
            promise.setFailure(t);
            return promise;
        }
    }

    @Deprecated
    @Override
    public ChannelFuture register(Channel channel, ChannelPromise promise) {
        if (channel == null) {
            throw new NullPointerException("channel");
        }
        try {
            return nextChild().register(channel, promise);
        } catch (Throwable t) {
            promise.setFailure(t);
            return promise;
        }
    }

    private EventLoop nextChild() throws Exception {
        if (shuttingDown) {
            throw new RejectedExecutionException("shutting down");
        }

        EventLoop loop = idleChildren.poll();
        if (loop == null) {
            if (maxChannels > 0 && activeChildren.size() >= maxChannels) {
                throw tooManyChannels;
            }
            loop = newChild(childArgs);
            loop.terminationFuture().addListener(childTerminationListener);
        }
        activeChildren.add(loop);
        return loop;
    }
}




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