Java tutorial
/* * 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.handler.timeout; import io.netty.bootstrap.ServerBootstrap; import io.netty.channel.Channel; import io.netty.channel.ChannelDuplexHandler; import io.netty.channel.ChannelFuture; import io.netty.channel.ChannelFutureListener; import io.netty.channel.ChannelHandlerContext; import io.netty.channel.ChannelInitializer; import io.netty.channel.ChannelOutboundHandlerAdapter; import io.netty.channel.ChannelPromise; import io.netty.util.internal.ObjectUtil; import java.util.concurrent.ScheduledFuture; import java.util.concurrent.TimeUnit; /** * Raises a {@link WriteTimeoutException} when a write operation cannot finish in a certain period of time. * * <pre> * // The connection is closed when a write operation cannot finish in 30 seconds. * * public class MyChannelInitializer extends {@link ChannelInitializer}<{@link Channel}> { * public void initChannel({@link Channel} channel) { * channel.pipeline().addLast("writeTimeoutHandler", new {@link WriteTimeoutHandler}(30); * channel.pipeline().addLast("myHandler", new MyHandler()); * } * } * * // Handler should handle the {@link WriteTimeoutException}. * public class MyHandler extends {@link ChannelDuplexHandler} { * {@code @Override} * public void exceptionCaught({@link ChannelHandlerContext} ctx, {@link Throwable} cause) * throws {@link Exception} { * if (cause instanceof {@link WriteTimeoutException}) { * // do something * } else { * super.exceptionCaught(ctx, cause); * } * } * } * * {@link ServerBootstrap} bootstrap = ...; * ... * bootstrap.childHandler(new MyChannelInitializer()); * ... * </pre> * @see ReadTimeoutHandler * @see IdleStateHandler */ public class WriteTimeoutHandler extends ChannelOutboundHandlerAdapter { private static final long MIN_TIMEOUT_NANOS = TimeUnit.MILLISECONDS.toNanos(1); private final long timeoutNanos; /** * A doubly-linked list to track all WriteTimeoutTasks */ private WriteTimeoutTask lastTask; private boolean closed; /** * Creates a new instance. * * @param timeoutSeconds * write timeout in seconds */ public WriteTimeoutHandler(int timeoutSeconds) { this(timeoutSeconds, TimeUnit.SECONDS); } /** * Creates a new instance. * * @param timeout * write timeout * @param unit * the {@link TimeUnit} of {@code timeout} */ public WriteTimeoutHandler(long timeout, TimeUnit unit) { ObjectUtil.checkNotNull(unit, "unit"); if (timeout <= 0) { timeoutNanos = 0; } else { timeoutNanos = Math.max(unit.toNanos(timeout), MIN_TIMEOUT_NANOS); } } @Override public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) throws Exception { if (timeoutNanos > 0) { promise = promise.unvoid(); scheduleTimeout(ctx, promise); } ctx.write(msg, promise); } @Override public void handlerRemoved(ChannelHandlerContext ctx) throws Exception { WriteTimeoutTask task = lastTask; lastTask = null; while (task != null) { task.scheduledFuture.cancel(false); WriteTimeoutTask prev = task.prev; task.prev = null; task.next = null; task = prev; } } private void scheduleTimeout(final ChannelHandlerContext ctx, final ChannelPromise promise) { // Schedule a timeout. final WriteTimeoutTask task = new WriteTimeoutTask(ctx, promise); task.scheduledFuture = ctx.executor().schedule(task, timeoutNanos, TimeUnit.NANOSECONDS); if (!task.scheduledFuture.isDone()) { addWriteTimeoutTask(task); // Cancel the scheduled timeout if the flush promise is complete. promise.addListener(task); } } private void addWriteTimeoutTask(WriteTimeoutTask task) { if (lastTask != null) { lastTask.next = task; task.prev = lastTask; } lastTask = task; } private void removeWriteTimeoutTask(WriteTimeoutTask task) { if (task == lastTask) { // task is the tail of list assert task.next == null; lastTask = lastTask.prev; if (lastTask != null) { lastTask.next = null; } } else if (task.prev == null && task.next == null) { // Since task is not lastTask, then it has been removed or not been added. return; } else if (task.prev == null) { // task is the head of list and the list has at least 2 nodes task.next.prev = null; } else { task.prev.next = task.next; task.next.prev = task.prev; } task.prev = null; task.next = null; } /** * Is called when a write timeout was detected */ protected void writeTimedOut(ChannelHandlerContext ctx) throws Exception { if (!closed) { ctx.fireExceptionCaught(WriteTimeoutException.INSTANCE); ctx.close(); closed = true; } } private final class WriteTimeoutTask implements Runnable, ChannelFutureListener { private final ChannelHandlerContext ctx; private final ChannelPromise promise; // WriteTimeoutTask is also a node of a doubly-linked list WriteTimeoutTask prev; WriteTimeoutTask next; ScheduledFuture<?> scheduledFuture; WriteTimeoutTask(ChannelHandlerContext ctx, ChannelPromise promise) { this.ctx = ctx; this.promise = promise; } @Override public void run() { // Was not written yet so issue a write timeout // The promise itself will be failed with a ClosedChannelException once the close() was issued // See https://github.com/netty/netty/issues/2159 if (!promise.isDone()) { try { writeTimedOut(ctx); } catch (Throwable t) { ctx.fireExceptionCaught(t); } } removeWriteTimeoutTask(this); } @Override public void operationComplete(ChannelFuture future) throws Exception { // scheduledFuture has already be set when reaching here scheduledFuture.cancel(false); removeWriteTimeoutTask(this); } } }