694 lines
22 KiB
Java
694 lines
22 KiB
Java
/*
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* Copyright 2013 The Netty Project
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*
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* The Netty Project licenses this file to you under the Apache License,
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* version 2.0 (the "License"); you may not use this file except in compliance
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* with the License. You may obtain a copy of the License at:
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*
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* https://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.util.concurrent;
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import io.netty.util.internal.StringUtil;
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import io.netty.util.internal.ThrowableUtil;
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import io.netty.util.internal.logging.InternalLogger;
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import io.netty.util.internal.logging.InternalLoggerFactory;
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import java.util.concurrent.CancellationException;
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import java.util.concurrent.CompletionException;
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import java.util.concurrent.ExecutionException;
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import java.util.concurrent.TimeUnit;
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import java.util.concurrent.TimeoutException;
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import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;
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import static java.util.Objects.requireNonNull;
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import static java.util.concurrent.TimeUnit.MILLISECONDS;
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public class DefaultPromise<V> implements Promise<V>, Future<V> {
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private static final InternalLogger logger = InternalLoggerFactory.getInstance(DefaultPromise.class);
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private static final InternalLogger rejectedExecutionLogger =
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InternalLoggerFactory.getInstance(DefaultPromise.class.getName() + ".rejectedExecution");
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@SuppressWarnings("rawtypes")
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private static final AtomicReferenceFieldUpdater<DefaultPromise, Object> RESULT_UPDATER =
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AtomicReferenceFieldUpdater.newUpdater(DefaultPromise.class, Object.class, "result");
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private static final Object SUCCESS = new Object();
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private static final Object UNCANCELLABLE = new Object();
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private static final CauseHolder CANCELLATION_CAUSE_HOLDER = new CauseHolder(
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StacklessCancellationException.newInstance(DefaultPromise.class, "cancel(...)"));
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private static final StackTraceElement[] CANCELLATION_STACK = CANCELLATION_CAUSE_HOLDER.cause.getStackTrace();
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static final Object NULL_CONTEXT = new Object();
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private volatile Object result;
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private final EventExecutor executor;
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// It is fine to not make this volatile as even if we override the value in there it does not matter as
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// DefaultFutureCompletionStage has no state itself and is just a wrapper around this DefaultPromise instance.
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private DefaultFutureCompletionStage<V> stage;
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/**
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* One or more listeners. Can be a {@link FutureListener} or a {@link DefaultFutureListeners}.
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* If {@code null}, it means either 1) no listeners were added yet or 2) all listeners were notified.
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* <p>
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* Note that if a {@link FutureContextListener} is added, we immediately upgrade to a {@link DefaultFutureListeners}
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* as we otherwise wouldn't have room to store the associated context object.
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* <p>
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* Threading - synchronized(this). We must support adding listeners when there is no EventExecutor.
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*/
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private Object listeners;
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/**
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* Threading - synchronized(this). We are required to hold the monitor to use Java's underlying wait()/notifyAll().
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*/
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private short waiters;
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/**
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* Creates a new unfulfilled promise.
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*
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* It is preferable to use {@link EventExecutor#newPromise()} to create a new promise
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*
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* @param executor
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* The {@link EventExecutor} which is used to notify the promise once it is complete.
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* It is assumed this executor will protect against {@link StackOverflowError} exceptions.
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* The executor may be used to avoid {@link StackOverflowError} by executing a {@link Runnable} if the stack
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* depth exceeds a threshold.
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*/
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public DefaultPromise(EventExecutor executor) {
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this.executor = requireNonNull(executor, "executor");
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stage = new DefaultFutureCompletionStage<>(this);
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}
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/**
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* Creates a new promise that has already been completed successfully.
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*
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* @param executor
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* The {@link EventExecutor} which is used to notify the promise once it is complete.
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* It is assumed this executor will protect against {@link StackOverflowError} exceptions.
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* The executor may be used to avoid {@link StackOverflowError} by executing a {@link Runnable} if the stack
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* depth exceeds a threshold.
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* @param result The result of the successful promise.
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*/
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public static <V> Promise<V> newSuccessfulPromise(EventExecutor executor, V result) {
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return new DefaultPromise<>(executor, result);
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}
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/**
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* Creates a new promise that has already failed.
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*
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* @param executor
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* The {@link EventExecutor} which is used to notify the promise once it is complete.
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* It is assumed this executor will protect against {@link StackOverflowError} exceptions.
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* The executor may be used to avoid {@link StackOverflowError} by executing a {@link Runnable} if the stack
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* depth exceeds a threshold.
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* @param cause The {@link Throwable} that caused the failure of the returned promise.
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*/
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public static <V> Promise<V> newFailedPromise(EventExecutor executor, Throwable cause) {
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return new DefaultPromise<>(cause, executor);
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}
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private DefaultPromise(EventExecutor executor, Object result) {
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this.executor = requireNonNull(executor, "executor");
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this.result = result == null? SUCCESS : result;
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stage = new DefaultFutureCompletionStage<>(this);
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}
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private DefaultPromise(Throwable cause, EventExecutor executor) {
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this.executor = requireNonNull(executor, "executor");
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result = new CauseHolder(requireNonNull(cause, "cause"));
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stage = new DefaultFutureCompletionStage<>(this);
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}
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@Override
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public Promise<V> setSuccess(V result) {
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if (setSuccess0(result)) {
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return this;
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}
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throw new IllegalStateException("complete already: " + this);
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}
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@Override
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public boolean trySuccess(V result) {
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return setSuccess0(result);
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}
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@Override
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public Promise<V> setFailure(Throwable cause) {
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if (setFailure0(cause)) {
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return this;
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}
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throw new IllegalStateException("complete already: " + this, cause);
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}
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@Override
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public boolean tryFailure(Throwable cause) {
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return setFailure0(cause);
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}
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@Override
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public boolean setUncancellable() {
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if (RESULT_UPDATER.compareAndSet(this, null, UNCANCELLABLE)) {
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return true;
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}
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Object result = this.result;
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return !isDone0(result) || !isCancelled0(result);
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}
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@Override
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public Future<V> asFuture() {
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return this;
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}
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@Override
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public boolean isSuccess() {
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Object result = this.result;
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return result != null && result != UNCANCELLABLE && !(result instanceof CauseHolder);
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}
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@Override
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public boolean isFailed() {
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return result instanceof CauseHolder;
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}
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@Override
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public boolean isCancellable() {
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return result == null;
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}
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private static final class LeanCancellationException extends CancellationException {
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private static final long serialVersionUID = 2794674970981187807L;
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// Suppress a warning since the method doesn't need synchronization
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@Override
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public Throwable fillInStackTrace() { // lgtm[java/non-sync-override]
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setStackTrace(CANCELLATION_STACK);
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return this;
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}
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@Override
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public String toString() {
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return CancellationException.class.getName();
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}
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}
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@Override
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public Throwable cause() {
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return cause0(result);
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}
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private Throwable cause0(Object result) {
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if (!isDone0(result)) {
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throw new IllegalStateException("Cannot call cause() on a future that has not completed.");
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}
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if (!(result instanceof CauseHolder)) {
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return null;
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}
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if (result == CANCELLATION_CAUSE_HOLDER) {
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CancellationException ce = new LeanCancellationException();
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if (RESULT_UPDATER.compareAndSet(this, CANCELLATION_CAUSE_HOLDER, new CauseHolder(ce))) {
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return ce;
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}
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result = this.result;
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}
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return ((CauseHolder) result).cause;
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}
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@Override
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public Future<V> addListener(FutureListener<? super V> listener) {
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requireNonNull(listener, "listener");
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addListener0(listener, null);
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if (isDone()) {
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notifyListeners();
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}
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return this;
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}
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@Override
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public <C> Future<V> addListener(C context, FutureContextListener<? super C, ? super V> listener) {
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requireNonNull(listener, "listener");
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addListener0(listener, context == null ? NULL_CONTEXT : context);
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if (isDone()) {
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notifyListeners();
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}
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return this;
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}
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@Override
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public Future<V> await() throws InterruptedException {
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if (isDone()) {
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return this;
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}
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if (Thread.interrupted()) {
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throw new InterruptedException(toString());
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}
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checkDeadLock();
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synchronized (this) {
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while (!isDone()) {
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incWaiters();
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try {
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wait();
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} finally {
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decWaiters();
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}
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}
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}
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return this;
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}
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@Override
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public Future<V> awaitUninterruptibly() {
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if (isDone()) {
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return this;
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}
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checkDeadLock();
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boolean interrupted = false;
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synchronized (this) {
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while (!isDone()) {
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incWaiters();
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try {
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wait();
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} catch (InterruptedException e) {
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// Interrupted while waiting.
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interrupted = true;
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} finally {
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decWaiters();
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}
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}
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}
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if (interrupted) {
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Thread.currentThread().interrupt();
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}
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return this;
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}
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@Override
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public boolean await(long timeout, TimeUnit unit) throws InterruptedException {
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return await0(unit.toNanos(timeout), true);
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}
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@Override
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public boolean await(long timeoutMillis) throws InterruptedException {
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return await0(MILLISECONDS.toNanos(timeoutMillis), true);
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}
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@Override
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public boolean awaitUninterruptibly(long timeout, TimeUnit unit) {
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try {
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return await0(unit.toNanos(timeout), false);
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} catch (InterruptedException e) {
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// Should not be raised at all.
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throw new InternalError();
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}
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}
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@Override
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public boolean awaitUninterruptibly(long timeoutMillis) {
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try {
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return await0(MILLISECONDS.toNanos(timeoutMillis), false);
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} catch (InterruptedException e) {
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// Should not be raised at all.
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throw new InternalError();
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}
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}
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@SuppressWarnings("unchecked")
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@Override
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public V getNow() {
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Object result = this.result;
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if (!isDone0(result)) {
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throw new IllegalStateException("Cannot call getNow() on a future that has not completed.");
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}
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if (result instanceof CauseHolder || result == SUCCESS) {
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return null;
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}
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return (V) result;
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}
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@SuppressWarnings("unchecked")
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@Override
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public V get() throws InterruptedException, ExecutionException {
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Object result = this.result;
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if (!isDone0(result)) {
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await();
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result = this.result;
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}
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if (result == SUCCESS || result == UNCANCELLABLE) {
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return null;
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}
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Throwable cause = cause0(result);
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if (cause == null) {
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return (V) result;
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}
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if (cause instanceof CancellationException) {
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throw (CancellationException) cause;
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}
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throw new ExecutionException(cause);
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}
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@SuppressWarnings("unchecked")
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@Override
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public V get(long timeout, TimeUnit unit) throws InterruptedException, ExecutionException, TimeoutException {
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Object result = this.result;
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if (!isDone0(result)) {
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if (!await(timeout, unit)) {
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throw new TimeoutException();
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}
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result = this.result;
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}
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if (result == SUCCESS || result == UNCANCELLABLE) {
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return null;
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}
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Throwable cause = cause0(result);
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if (cause == null) {
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return (V) result;
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}
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if (cause instanceof CancellationException) {
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throw (CancellationException) cause;
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}
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throw new ExecutionException(cause);
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}
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@Override
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public boolean cancel() {
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return cancel(false);
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}
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/**
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* @param mayInterruptIfRunning this value has no effect in this implementation.
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*/
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@Override
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public boolean cancel(boolean mayInterruptIfRunning) {
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if (RESULT_UPDATER.compareAndSet(this, null, CANCELLATION_CAUSE_HOLDER)) {
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if (checkNotifyWaiters()) {
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notifyListeners();
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}
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return true;
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}
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return false;
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}
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@Override
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public boolean isCancelled() {
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return isCancelled0(result);
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}
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@Override
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public boolean isDone() {
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return isDone0(result);
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}
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@Override
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public Future<V> sync() throws InterruptedException {
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await();
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rethrowIfFailed();
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return this;
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}
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@Override
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public Future<V> syncUninterruptibly() {
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awaitUninterruptibly();
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rethrowIfFailed();
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return this;
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}
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@Override
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public String toString() {
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return toStringBuilder().toString();
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}
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protected StringBuilder toStringBuilder() {
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StringBuilder buf = new StringBuilder(64)
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.append(StringUtil.simpleClassName(this))
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.append('@')
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.append(Integer.toHexString(hashCode()));
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Object result = this.result;
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if (result == SUCCESS) {
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buf.append("(success)");
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} else if (result == UNCANCELLABLE) {
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buf.append("(uncancellable)");
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} else if (result instanceof CauseHolder) {
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buf.append("(failure: ")
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.append(((CauseHolder) result).cause)
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.append(')');
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} else if (result != null) {
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buf.append("(success: ")
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.append(result)
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.append(')');
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} else {
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buf.append("(incomplete)");
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}
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return buf;
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}
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/**
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* Get the executor used to notify listeners when this promise is complete.
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* <p>
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* It is assumed this executor will protect against {@link StackOverflowError} exceptions.
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* The executor may be used to avoid {@link StackOverflowError} by executing a {@link Runnable} if the stack
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* depth exceeds a threshold.
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* @return The executor used to notify listeners when this promise is complete.
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*/
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@Override
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public final EventExecutor executor() {
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return executor;
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}
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protected void checkDeadLock() {
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checkDeadLock(executor);
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}
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protected final void checkDeadLock(EventExecutor executor) {
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if (executor.inEventLoop()) {
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throw new BlockingOperationException(toString());
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}
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}
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private void notifyListeners() {
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safeExecute(executor(), this::notifyListenersNow);
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}
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@SuppressWarnings("unchecked")
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private void notifyListenersNow() {
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Object listeners;
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synchronized (this) {
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// Only proceed if there are listeners to notify.
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if (this.listeners == null) {
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return;
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}
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listeners = this.listeners;
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this.listeners = null;
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}
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for (;;) {
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if (listeners instanceof DefaultFutureListeners) {
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notifyListeners0((DefaultFutureListeners) listeners);
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} else {
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notifyListener0(this, (FutureListener<V>) listeners);
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}
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synchronized (this) {
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if (this.listeners == null) {
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return;
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}
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listeners = this.listeners;
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this.listeners = null;
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}
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}
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}
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private void notifyListeners0(DefaultFutureListeners listeners) {
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listeners.notifyListeners(this, logger);
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}
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static <V> void notifyListener0(Future<V> future, FutureListener<? super V> l) {
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try {
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l.operationComplete(future);
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} catch (Throwable t) {
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if (logger.isWarnEnabled()) {
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logger.warn("An exception was thrown by " + l.getClass().getName() + ".operationComplete()", t);
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}
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}
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}
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private synchronized void addListener0(Object listener, Object context) {
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if (listeners == null && context == null) {
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listeners = listener;
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} else if (listeners instanceof DefaultFutureListeners) {
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((DefaultFutureListeners) listeners).add(listener, context);
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} else {
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DefaultFutureListeners listeners = new DefaultFutureListeners();
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if (this.listeners != null) {
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listeners.add(this.listeners, null);
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}
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listeners.add(listener, context);
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this.listeners = listeners;
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}
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}
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private boolean setSuccess0(V result) {
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return setValue0(result == null ? SUCCESS : result);
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}
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private boolean setFailure0(Throwable cause) {
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return setValue0(new CauseHolder(requireNonNull(cause, "cause")));
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}
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private boolean setValue0(Object objResult) {
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if (RESULT_UPDATER.compareAndSet(this, null, objResult) ||
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RESULT_UPDATER.compareAndSet(this, UNCANCELLABLE, objResult)) {
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if (checkNotifyWaiters()) {
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notifyListeners();
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}
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return true;
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}
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return false;
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}
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/**
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* Check if there are any waiters and if so notify these.
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* @return {@code true} if there are any listeners attached to the promise, {@code false} otherwise.
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*/
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private synchronized boolean checkNotifyWaiters() {
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if (waiters > 0) {
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notifyAll();
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}
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return listeners != null;
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}
|
|
|
|
private void incWaiters() {
|
|
if (waiters == Short.MAX_VALUE) {
|
|
throw new IllegalStateException("too many waiters: " + this);
|
|
}
|
|
++waiters;
|
|
}
|
|
|
|
private void decWaiters() {
|
|
--waiters;
|
|
}
|
|
|
|
private void rethrowIfFailed() {
|
|
Throwable cause = cause();
|
|
if (cause == null) {
|
|
return;
|
|
}
|
|
if (cause instanceof CancellationException) {
|
|
throw (CancellationException) cause;
|
|
}
|
|
throw new CompletionException(cause);
|
|
}
|
|
|
|
private boolean await0(long timeoutNanos, boolean interruptable) throws InterruptedException {
|
|
if (isDone()) {
|
|
return true;
|
|
}
|
|
|
|
if (timeoutNanos <= 0) {
|
|
return isDone();
|
|
}
|
|
|
|
if (interruptable && Thread.interrupted()) {
|
|
throw new InterruptedException(toString());
|
|
}
|
|
|
|
checkDeadLock();
|
|
|
|
// Start counting time from here instead of the first line of this method,
|
|
// to avoid/postpone performance cost of System.nanoTime().
|
|
final long startTime = System.nanoTime();
|
|
synchronized (this) {
|
|
boolean interrupted = false;
|
|
try {
|
|
long waitTime = timeoutNanos;
|
|
while (!isDone() && waitTime > 0) {
|
|
incWaiters();
|
|
try {
|
|
wait(waitTime / 1000000, (int) (waitTime % 1000000));
|
|
} catch (InterruptedException e) {
|
|
if (interruptable) {
|
|
throw e;
|
|
} else {
|
|
interrupted = true;
|
|
}
|
|
} finally {
|
|
decWaiters();
|
|
}
|
|
// Check isDone() in advance, try to avoid calculating the elapsed time later.
|
|
if (isDone()) {
|
|
return true;
|
|
}
|
|
// Calculate the elapsed time here instead of in the while condition,
|
|
// try to avoid performance cost of System.nanoTime() in the first loop of while.
|
|
waitTime = timeoutNanos - (System.nanoTime() - startTime);
|
|
}
|
|
return isDone();
|
|
} finally {
|
|
if (interrupted) {
|
|
Thread.currentThread().interrupt();
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
private static boolean isCancelled0(Object result) {
|
|
return result instanceof CauseHolder && ((CauseHolder) result).cause instanceof CancellationException;
|
|
}
|
|
|
|
private static boolean isDone0(Object result) {
|
|
return result != null && result != UNCANCELLABLE;
|
|
}
|
|
|
|
private static final class CauseHolder {
|
|
final Throwable cause;
|
|
CauseHolder(Throwable cause) {
|
|
this.cause = cause;
|
|
}
|
|
}
|
|
|
|
static void safeExecute(EventExecutor executor, Runnable task) {
|
|
try {
|
|
executor.execute(task);
|
|
} catch (Throwable t) {
|
|
rejectedExecutionLogger.error("Failed to submit a listener notification task. Event loop shut down?", t);
|
|
}
|
|
}
|
|
|
|
@Override
|
|
public FutureCompletionStage<V> asStage() {
|
|
DefaultFutureCompletionStage<V> stageAdapter = stage;
|
|
if (stageAdapter == null) {
|
|
stage = stageAdapter = new DefaultFutureCompletionStage<>(this);
|
|
}
|
|
return stageAdapter;
|
|
}
|
|
|
|
private static final class StacklessCancellationException extends CancellationException {
|
|
|
|
private static final long serialVersionUID = -2974906711413716191L;
|
|
|
|
// Override fillInStackTrace() so we not populate the backtrace via a native call and so leak the
|
|
// Classloader.
|
|
@Override
|
|
public Throwable fillInStackTrace() {
|
|
return this;
|
|
}
|
|
|
|
static StacklessCancellationException newInstance(Class<?> clazz, String method) {
|
|
return ThrowableUtil.unknownStackTrace(new StacklessCancellationException(), clazz, method);
|
|
}
|
|
}
|
|
}
|