258 lines
9.9 KiB
Java
258 lines
9.9 KiB
Java
/*
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* Copyright 2009 Red Hat, Inc.
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*
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* Red Hat licenses this file to you under the Apache License, version 2.0
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* (the "License"); you may not use this file except in compliance with the
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* License. You may obtain a copy of the License at:
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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*/
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package io.netty.channel.group;
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import java.util.Iterator;
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import java.util.concurrent.TimeUnit;
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import io.netty.channel.Channel;
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import io.netty.channel.ChannelFuture;
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import io.netty.channel.ChannelHandler;
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import io.netty.channel.ChannelHandlerContext;
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import io.netty.channel.ChannelPipeline;
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import io.netty.channel.MessageEvent;
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import io.netty.handler.execution.ExecutionHandler;
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/**
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* The result of an asynchronous {@link ChannelGroup} operation.
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* {@link ChannelGroupFuture} is composed of {@link ChannelFuture}s which
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* represent the outcome of the individual I/O operations that affect the
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* {@link Channel}s in the {@link ChannelGroup}.
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*
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* <p>
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* All I/O operations in {@link ChannelGroup} are asynchronous. It means any
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* I/O calls will return immediately with no guarantee that the requested I/O
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* operations have been completed at the end of the call. Instead, you will be
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* returned with a {@link ChannelGroupFuture} instance which tells you when the
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* requested I/O operations have succeeded, failed, or cancelled.
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* <p>
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* Various methods are provided to let you check if the I/O operations has been
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* completed, wait for the completion, and retrieve the result of the I/O
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* operation. It also allows you to add more than one
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* {@link ChannelGroupFutureListener} so you can get notified when the I/O
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* operation have been completed.
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*
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* <h3>Prefer {@link #addListener(ChannelGroupFutureListener)} to {@link #await()}</h3>
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*
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* It is recommended to prefer {@link #addListener(ChannelGroupFutureListener)} to
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* {@link #await()} wherever possible to get notified when I/O operations are
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* done and to do any follow-up tasks.
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* <p>
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* {@link #addListener(ChannelGroupFutureListener)} is non-blocking. It simply
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* adds the specified {@link ChannelGroupFutureListener} to the
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* {@link ChannelGroupFuture}, and I/O thread will notify the listeners when
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* the I/O operations associated with the future is done.
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* {@link ChannelGroupFutureListener} yields the best performance and resource
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* utilization because it does not block at all, but it could be tricky to
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* implement a sequential logic if you are not used to event-driven programming.
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* <p>
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* By contrast, {@link #await()} is a blocking operation. Once called, the
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* caller thread blocks until all I/O operations are done. It is easier to
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* implement a sequential logic with {@link #await()}, but the caller thread
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* blocks unnecessarily until all I/O operations are done and there's relatively
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* expensive cost of inter-thread notification. Moreover, there's a chance of
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* dead lock in a particular circumstance, which is described below.
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*
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* <h3>Do not call {@link #await()} inside {@link ChannelHandler}</h3>
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* <p>
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* The event handler methods in {@link ChannelHandler} is often called by
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* an I/O thread unless an {@link ExecutionHandler} is in the
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* {@link ChannelPipeline}. If {@link #await()} is called by an event handler
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* method, which is called by the I/O thread, the I/O operation it is waiting
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* for might never be complete because {@link #await()} can block the I/O
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* operation it is waiting for, which is a dead lock.
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* <pre>
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* // BAD - NEVER DO THIS
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* {@code @Override}
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* public void messageReceived({@link ChannelHandlerContext} ctx, {@link MessageEvent} e) {
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* if (e.getMessage() instanceof ShutdownMessage) {
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* {@link ChannelGroup} allChannels = MyServer.getAllChannels();
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* {@link ChannelGroupFuture} future = allChannels.close();
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* future.awaitUninterruptibly();
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* // Perform post-shutdown operation
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* // ...
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* }
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* }
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*
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* // GOOD
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* {@code @Override}
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* public void messageReceived(ChannelHandlerContext ctx, MessageEvent e) {
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* if (e.getMessage() instanceof ShutdownMessage) {
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* {@link ChannelGroup} allChannels = MyServer.getAllChannels();
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* {@link ChannelGroupFuture} future = allChannels.close();
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* future.addListener(new {@link ChannelGroupFutureListener}() {
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* public void operationComplete({@link ChannelGroupFuture} future) {
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* // Perform post-closure operation
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* // ...
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* }
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* });
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* }
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* }
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* </pre>
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* <p>
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* In spite of the disadvantages mentioned above, there are certainly the cases
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* where it is more convenient to call {@link #await()}. In such a case, please
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* make sure you do not call {@link #await()} in an I/O thread. Otherwise,
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* {@link IllegalStateException} will be raised to prevent a dead lock.
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*
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* @author <a href="http://netty.io/">The Netty Project</a>
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* @author <a href="http://gleamynode.net/">Trustin Lee</a>
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*
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* @apiviz.owns io.netty.channel.group.ChannelGroupFutureListener - - notifies
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*/
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public interface ChannelGroupFuture extends Iterable<ChannelFuture> {
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/**
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* Returns the {@link ChannelGroup} which is associated with this future.
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*/
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ChannelGroup getGroup();
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/**
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* Returns the {@link ChannelFuture} of the individual I/O operation which
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* is associated with the {@link Channel} whose ID matches the specified
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* integer.
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*
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* @return the matching {@link ChannelFuture} if found.
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* {@code null} otherwise.
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*/
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ChannelFuture find(Integer channelId);
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/**
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* Returns the {@link ChannelFuture} of the individual I/O operation which
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* is associated with the specified {@link Channel}.
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*
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* @return the matching {@link ChannelFuture} if found.
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* {@code null} otherwise.
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*/
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ChannelFuture find(Channel channel);
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/**
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* Returns {@code true} if and only if this future is
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* complete, regardless of whether the operation was successful, failed,
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* or canceled.
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*/
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boolean isDone();
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/**
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* Returns {@code true} if and only if all I/O operations associated with
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* this future were successful without any failure.
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*/
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boolean isCompleteSuccess();
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/**
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* Returns {@code true} if and only if the I/O operations associated with
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* this future were partially successful with some failure.
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*/
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boolean isPartialSuccess();
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/**
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* Returns {@code true} if and only if all I/O operations associated with
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* this future have failed without any success.
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*/
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boolean isCompleteFailure();
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/**
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* Returns {@code true} if and only if the I/O operations associated with
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* this future have failed partially with some success.
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*/
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boolean isPartialFailure();
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/**
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* Adds the specified listener to this future. The
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* specified listener is notified when this future is
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* {@linkplain #isDone() done}. If this future is already
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* completed, the specified listener is notified immediately.
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*/
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void addListener(ChannelGroupFutureListener listener);
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/**
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* Removes the specified listener from this future.
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* The specified listener is no longer notified when this
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* future is {@linkplain #isDone() done}. If this
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* future is already completed, this method has no effect
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* and returns silently.
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*/
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void removeListener(ChannelGroupFutureListener listener);
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/**
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* Waits for this future to be completed.
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*
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* @throws InterruptedException
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* if the current thread was interrupted
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*/
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ChannelGroupFuture await() throws InterruptedException;
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/**
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* Waits for this future to be completed without
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* interruption. This method catches an {@link InterruptedException} and
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* discards it silently.
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*/
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ChannelGroupFuture awaitUninterruptibly();
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/**
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* Waits for this future to be completed within the
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* specified time limit.
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*
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* @return {@code true} if and only if the future was completed within
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* the specified time limit
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*
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* @throws InterruptedException
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* if the current thread was interrupted
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*/
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boolean await(long timeout, TimeUnit unit) throws InterruptedException;
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/**
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* Waits for this future to be completed within the
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* specified time limit.
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*
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* @return {@code true} if and only if the future was completed within
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* the specified time limit
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*
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* @throws InterruptedException
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* if the current thread was interrupted
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*/
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boolean await(long timeoutMillis) throws InterruptedException;
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/**
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* Waits for this future to be completed within the
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* specified time limit without interruption. This method catches an
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* {@link InterruptedException} and discards it silently.
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*
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* @return {@code true} if and only if the future was completed within
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* the specified time limit
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*/
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boolean awaitUninterruptibly(long timeout, TimeUnit unit);
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/**
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* Waits for this future to be completed within the
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* specified time limit without interruption. This method catches an
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* {@link InterruptedException} and discards it silently.
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*
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* @return {@code true} if and only if the future was completed within
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* the specified time limit
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*/
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boolean awaitUninterruptibly(long timeoutMillis);
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/**
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* Returns the {@link Iterator} that enumerates all {@link ChannelFuture}s
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* which are associated with this future. Please note that the returned
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* {@link Iterator} is is unmodifiable, which means a {@link ChannelFuture}
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* cannot be removed from this future.
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*/
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@Override
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Iterator<ChannelFuture> iterator();
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}
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