Java tutorial
/* * Copyright 2015 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.pool; import io.netty.bootstrap.Bootstrap; import io.netty.channel.Channel; 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.internal.ObjectUtil; import java.nio.channels.ClosedChannelException; import java.util.ArrayDeque; import java.util.Queue; import java.util.concurrent.atomic.AtomicInteger; import java.util.concurrent.Callable; import java.util.concurrent.ScheduledFuture; import java.util.concurrent.TimeUnit; import java.util.concurrent.TimeoutException; /** * {@link ChannelPool} implementation that takes another {@link ChannelPool} implementation and enforce a maximum * number of concurrent connections. */ public class FixedChannelPool extends SimpleChannelPool { public enum AcquireTimeoutAction { /** * Create a new connection when the timeout is detected. */ NEW, /** * Fail the {@link Future} of the acquire call with a {@link TimeoutException}. */ FAIL } private final EventExecutor executor; private final long acquireTimeoutNanos; private final Runnable timeoutTask; // There is no need to worry about synchronization as everything that modified the queue or counts is done // by the above EventExecutor. private final Queue<AcquireTask> pendingAcquireQueue = new ArrayDeque<AcquireTask>(); private final int maxConnections; private final int maxPendingAcquires; private final AtomicInteger acquiredChannelCount = new AtomicInteger(); private int pendingAcquireCount; private boolean closed; /** * Creates a new instance using the {@link ChannelHealthChecker#ACTIVE}. * * @param bootstrap the{@link Bootstrap} that is used for connections * @param handler the {@link ChannelPoolHandler} that will be notified for the different pool actions * @param maxConnections the number of maximal active connections, once this is reached new tries to acquire * a {@link Channel} will be delayed until a connection is returned to the pool again. */ public FixedChannelPool(Bootstrap bootstrap, ChannelPoolHandler handler, int maxConnections) { this(bootstrap, handler, maxConnections, Integer.MAX_VALUE); } /** * Creates a new instance using the {@link ChannelHealthChecker#ACTIVE}. * * @param bootstrap the{@link Bootstrap} that is used for connections * @param handler the {@link ChannelPoolHandler} that will be notified for the different pool actions * @param maxConnections the number of maximal active connections, once this is reached new tries to * acquire a {@link Channel} will be delayed until a connection is returned to the * pool again. * @param maxPendingAcquires the maximum number of pending acquires. Once this is exceed acquire tries will * be failed. */ public FixedChannelPool(Bootstrap bootstrap, ChannelPoolHandler handler, int maxConnections, int maxPendingAcquires) { this(bootstrap, handler, ChannelHealthChecker.ACTIVE, null, -1, maxConnections, maxPendingAcquires); } /** * Creates a new instance. * * @param bootstrap the{@link Bootstrap} that is used for connections * @param handler the {@link ChannelPoolHandler} that will be notified for the different pool actions * @param healthCheck the {@link ChannelHealthChecker} that will be used to check if a {@link Channel} is * still healthy when obtain from the {@link ChannelPool} * @param action the {@link AcquireTimeoutAction} to use or {@code null} if non should be used. * In this case {@param acquireTimeoutMillis} must be {@code -1}. * @param acquireTimeoutMillis the time (in milliseconds) after which an pending acquire must complete or * the {@link AcquireTimeoutAction} takes place. * @param maxConnections the number of maximal active connections, once this is reached new tries to * acquire a {@link Channel} will be delayed until a connection is returned to the * pool again. * @param maxPendingAcquires the maximum number of pending acquires. Once this is exceed acquire tries will * be failed. */ public FixedChannelPool(Bootstrap bootstrap, ChannelPoolHandler handler, ChannelHealthChecker healthCheck, AcquireTimeoutAction action, final long acquireTimeoutMillis, int maxConnections, int maxPendingAcquires) { this(bootstrap, handler, healthCheck, action, acquireTimeoutMillis, maxConnections, maxPendingAcquires, true); } /** * Creates a new instance. * * @param bootstrap the{@link Bootstrap} that is used for connections * @param handler the {@link ChannelPoolHandler} that will be notified for the different pool actions * @param healthCheck the {@link ChannelHealthChecker} that will be used to check if a {@link Channel} is * still healthy when obtain from the {@link ChannelPool} * @param action the {@link AcquireTimeoutAction} to use or {@code null} if non should be used. * In this case {@param acquireTimeoutMillis} must be {@code -1}. * @param acquireTimeoutMillis the time (in milliseconds) after which an pending acquire must complete or * the {@link AcquireTimeoutAction} takes place. * @param maxConnections the number of maximal active connections, once this is reached new tries to * acquire a {@link Channel} will be delayed until a connection is returned to the * pool again. * @param maxPendingAcquires the maximum number of pending acquires. Once this is exceed acquire tries will * be failed. * @param releaseHealthCheck will check channel health before offering back if this parameter set to * {@code true}. */ public FixedChannelPool(Bootstrap bootstrap, ChannelPoolHandler handler, ChannelHealthChecker healthCheck, AcquireTimeoutAction action, final long acquireTimeoutMillis, int maxConnections, int maxPendingAcquires, final boolean releaseHealthCheck) { this(bootstrap, handler, healthCheck, action, acquireTimeoutMillis, maxConnections, maxPendingAcquires, releaseHealthCheck, true); } /** * Creates a new instance. * * @param bootstrap the{@link Bootstrap} that is used for connections * @param handler the {@link ChannelPoolHandler} that will be notified for the different pool actions * @param healthCheck the {@link ChannelHealthChecker} that will be used to check if a {@link Channel} is * still healthy when obtain from the {@link ChannelPool} * @param action the {@link AcquireTimeoutAction} to use or {@code null} if non should be used. * In this case {@param acquireTimeoutMillis} must be {@code -1}. * @param acquireTimeoutMillis the time (in milliseconds) after which an pending acquire must complete or * the {@link AcquireTimeoutAction} takes place. * @param maxConnections the number of maximal active connections, once this is reached new tries to * acquire a {@link Channel} will be delayed until a connection is returned to the * pool again. * @param maxPendingAcquires the maximum number of pending acquires. Once this is exceed acquire tries will * be failed. * @param releaseHealthCheck will check channel health before offering back if this parameter set to * {@code true}. * @param lastRecentUsed {@code true} {@link Channel} selection will be LIFO, if {@code false} FIFO. */ public FixedChannelPool(Bootstrap bootstrap, ChannelPoolHandler handler, ChannelHealthChecker healthCheck, AcquireTimeoutAction action, final long acquireTimeoutMillis, int maxConnections, int maxPendingAcquires, boolean releaseHealthCheck, boolean lastRecentUsed) { super(bootstrap, handler, healthCheck, releaseHealthCheck, lastRecentUsed); if (maxConnections < 1) { throw new IllegalArgumentException("maxConnections: " + maxConnections + " (expected: >= 1)"); } if (maxPendingAcquires < 1) { throw new IllegalArgumentException("maxPendingAcquires: " + maxPendingAcquires + " (expected: >= 1)"); } if (action == null && acquireTimeoutMillis == -1) { timeoutTask = null; acquireTimeoutNanos = -1; } else if (action == null && acquireTimeoutMillis != -1) { throw new NullPointerException("action"); } else if (action != null && acquireTimeoutMillis < 0) { throw new IllegalArgumentException( "acquireTimeoutMillis: " + acquireTimeoutMillis + " (expected: >= 0)"); } else { acquireTimeoutNanos = TimeUnit.MILLISECONDS.toNanos(acquireTimeoutMillis); switch (action) { case FAIL: timeoutTask = new TimeoutTask() { @Override public void onTimeout(AcquireTask task) { // Fail the promise as we timed out. task.promise.setFailure( new TimeoutException("Acquire operation took longer then configured maximum time") { @Override public synchronized Throwable fillInStackTrace() { return this; } }); } }; break; case NEW: timeoutTask = new TimeoutTask() { @Override public void onTimeout(AcquireTask task) { // Increment the acquire count and delegate to super to actually acquire a Channel which will // create a new connection. task.acquired(); FixedChannelPool.super.acquire(task.promise); } }; break; default: throw new Error(); } } executor = bootstrap.config().group().next(); this.maxConnections = maxConnections; this.maxPendingAcquires = maxPendingAcquires; } /** Returns the number of acquired channels that this pool thinks it has. */ public int acquiredChannelCount() { return acquiredChannelCount.get(); } @Override public Future<Channel> acquire(final Promise<Channel> promise) { try { if (executor.inEventLoop()) { acquire0(promise); } else { executor.execute(new Runnable() { @Override public void run() { acquire0(promise); } }); } } catch (Throwable cause) { promise.setFailure(cause); } return promise; } private void acquire0(final Promise<Channel> promise) { assert executor.inEventLoop(); if (closed) { promise.setFailure(new IllegalStateException("FixedChannelPool was closed")); return; } if (acquiredChannelCount.get() < maxConnections) { assert acquiredChannelCount.get() >= 0; // We need to create a new promise as we need to ensure the AcquireListener runs in the correct // EventLoop Promise<Channel> p = executor.newPromise(); AcquireListener l = new AcquireListener(promise); l.acquired(); p.addListener(l); super.acquire(p); } else { if (pendingAcquireCount >= maxPendingAcquires) { tooManyOutstanding(promise); } else { AcquireTask task = new AcquireTask(promise); if (pendingAcquireQueue.offer(task)) { ++pendingAcquireCount; if (timeoutTask != null) { task.timeoutFuture = executor.schedule(timeoutTask, acquireTimeoutNanos, TimeUnit.NANOSECONDS); } } else { tooManyOutstanding(promise); } } assert pendingAcquireCount > 0; } } private void tooManyOutstanding(Promise<?> promise) { promise.setFailure(new IllegalStateException("Too many outstanding acquire operations")); } @Override public Future<Void> release(final Channel channel, final Promise<Void> promise) { ObjectUtil.checkNotNull(promise, "promise"); final Promise<Void> p = executor.newPromise(); super.release(channel, p.addListener(new FutureListener<Void>() { @Override public void operationComplete(Future<Void> future) throws Exception { assert executor.inEventLoop(); if (closed) { // Since the pool is closed, we have no choice but to close the channel channel.close(); promise.setFailure(new IllegalStateException("FixedChannelPool was closed")); return; } if (future.isSuccess()) { decrementAndRunTaskQueue(); promise.setSuccess(null); } else { Throwable cause = future.cause(); // Check if the exception was not because of we passed the Channel to the wrong pool. if (!(cause instanceof IllegalArgumentException)) { decrementAndRunTaskQueue(); } promise.setFailure(future.cause()); } } })); return promise; } private void decrementAndRunTaskQueue() { // We should never have a negative value. int currentCount = acquiredChannelCount.decrementAndGet(); assert currentCount >= 0; // Run the pending acquire tasks before notify the original promise so if the user would // try to acquire again from the ChannelFutureListener and the pendingAcquireCount is >= // maxPendingAcquires we may be able to run some pending tasks first and so allow to add // more. runTaskQueue(); } private void runTaskQueue() { while (acquiredChannelCount.get() < maxConnections) { AcquireTask task = pendingAcquireQueue.poll(); if (task == null) { break; } // Cancel the timeout if one was scheduled ScheduledFuture<?> timeoutFuture = task.timeoutFuture; if (timeoutFuture != null) { timeoutFuture.cancel(false); } --pendingAcquireCount; task.acquired(); super.acquire(task.promise); } // We should never have a negative value. assert pendingAcquireCount >= 0; assert acquiredChannelCount.get() >= 0; } // AcquireTask extends AcquireListener to reduce object creations and so GC pressure private final class AcquireTask extends AcquireListener { final Promise<Channel> promise; final long expireNanoTime = System.nanoTime() + acquireTimeoutNanos; ScheduledFuture<?> timeoutFuture; AcquireTask(Promise<Channel> promise) { super(promise); // We need to create a new promise as we need to ensure the AcquireListener runs in the correct // EventLoop. this.promise = executor.<Channel>newPromise().addListener(this); } } private abstract class TimeoutTask implements Runnable { @Override public final void run() { assert executor.inEventLoop(); long nanoTime = System.nanoTime(); for (;;) { AcquireTask task = pendingAcquireQueue.peek(); // Compare nanoTime as descripted in the javadocs of System.nanoTime() // // See https://docs.oracle.com/javase/7/docs/api/java/lang/System.html#nanoTime() // See https://github.com/netty/netty/issues/3705 if (task == null || nanoTime - task.expireNanoTime < 0) { break; } pendingAcquireQueue.remove(); --pendingAcquireCount; onTimeout(task); } } public abstract void onTimeout(AcquireTask task); } private class AcquireListener implements FutureListener<Channel> { private final Promise<Channel> originalPromise; protected boolean acquired; AcquireListener(Promise<Channel> originalPromise) { this.originalPromise = originalPromise; } @Override public void operationComplete(Future<Channel> future) throws Exception { assert executor.inEventLoop(); if (closed) { if (future.isSuccess()) { // Since the pool is closed, we have no choice but to close the channel future.getNow().close(); } originalPromise.setFailure(new IllegalStateException("FixedChannelPool was closed")); return; } if (future.isSuccess()) { originalPromise.setSuccess(future.getNow()); } else { if (acquired) { decrementAndRunTaskQueue(); } else { runTaskQueue(); } originalPromise.setFailure(future.cause()); } } public void acquired() { if (acquired) { return; } acquiredChannelCount.incrementAndGet(); acquired = true; } } @Override public void close() { try { closeAsync().await(); } catch (InterruptedException e) { Thread.currentThread().interrupt(); throw new RuntimeException(e); } } /** * Closes the pool in an async manner. * * @return Future which represents completion of the close task */ @Override public Future<Void> closeAsync() { if (executor.inEventLoop()) { return close0(); } else { final Promise<Void> closeComplete = executor.newPromise(); executor.execute(new Runnable() { @Override public void run() { close0().addListener(new FutureListener<Void>() { @Override public void operationComplete(Future<Void> f) throws Exception { if (f.isSuccess()) { closeComplete.setSuccess(null); } else { closeComplete.setFailure(f.cause()); } } }); } }); return closeComplete; } } private Future<Void> close0() { assert executor.inEventLoop(); if (!closed) { closed = true; for (;;) { AcquireTask task = pendingAcquireQueue.poll(); if (task == null) { break; } ScheduledFuture<?> f = task.timeoutFuture; if (f != null) { f.cancel(false); } task.promise.setFailure(new ClosedChannelException()); } acquiredChannelCount.set(0); pendingAcquireCount = 0; // Ensure we dispatch this on another Thread as close0 will be called from the EventExecutor and we need // to ensure we will not block in a EventExecutor. return GlobalEventExecutor.INSTANCE.submit(new Callable<Void>() { @Override public Void call() throws Exception { FixedChannelPool.super.close(); return null; } }); } return GlobalEventExecutor.INSTANCE.newSucceededFuture(null); } }