DefaultPromise.java
/*
* Copyright 2013 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:
*
* https://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.util.concurrent;
import io.netty.util.internal.InternalThreadLocalMap;
import io.netty.util.internal.PlatformDependent;
import io.netty.util.internal.StringUtil;
import io.netty.util.internal.SystemPropertyUtil;
import io.netty.util.internal.ThrowableUtil;
import io.netty.util.internal.logging.InternalLogger;
import io.netty.util.internal.logging.InternalLoggerFactory;
import java.util.concurrent.CancellationException;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;
import static io.netty.util.internal.ObjectUtil.checkNotNull;
import static java.util.concurrent.TimeUnit.MILLISECONDS;
public class DefaultPromise<V> extends AbstractFuture<V> implements Promise<V> {
private static final InternalLogger logger = InternalLoggerFactory.getInstance(DefaultPromise.class);
private static final InternalLogger rejectedExecutionLogger =
InternalLoggerFactory.getInstance(DefaultPromise.class.getName() + ".rejectedExecution");
private static final int MAX_LISTENER_STACK_DEPTH = Math.min(8,
SystemPropertyUtil.getInt("io.netty.defaultPromise.maxListenerStackDepth", 8));
@SuppressWarnings("rawtypes")
private static final AtomicReferenceFieldUpdater<DefaultPromise, Object> RESULT_UPDATER =
AtomicReferenceFieldUpdater.newUpdater(DefaultPromise.class, Object.class, "result");
private static final Object SUCCESS = new Object();
private static final Object UNCANCELLABLE = new Object();
private static final CauseHolder CANCELLATION_CAUSE_HOLDER = new CauseHolder(
StacklessCancellationException.newInstance(DefaultPromise.class, "cancel(...)"));
private static final StackTraceElement[] CANCELLATION_STACK = CANCELLATION_CAUSE_HOLDER.cause.getStackTrace();
private volatile Object result;
private final EventExecutor executor;
/**
* One or more listeners. Can be a {@link GenericFutureListener} or a {@link DefaultFutureListeners}.
* If {@code null}, it means either 1) no listeners were added yet or 2) all listeners were notified.
*
* Threading - synchronized(this). We must support adding listeners when there is no EventExecutor.
*/
private GenericFutureListener<? extends Future<?>> listener;
private DefaultFutureListeners listeners;
/**
* Threading - synchronized(this). We are required to hold the monitor to use Java's underlying wait()/notifyAll().
*/
private short waiters;
/**
* Threading - synchronized(this). We must prevent concurrent notification and FIFO listener notification if the
* executor changes.
*/
private boolean notifyingListeners;
/**
* Creates a new instance.
*
* It is preferable to use {@link EventExecutor#newPromise()} to create a new promise
*
* @param executor
* the {@link EventExecutor} which is used to notify the promise once it is complete.
* It is assumed this executor will protect against {@link StackOverflowError} exceptions.
* The executor may be used to avoid {@link StackOverflowError} by executing a {@link Runnable} if the stack
* depth exceeds a threshold.
*
*/
public DefaultPromise(EventExecutor executor) {
this.executor = checkNotNull(executor, "executor");
}
/**
* See {@link #executor()} for expectations of the executor.
*/
protected DefaultPromise() {
// only for subclasses
executor = null;
}
@Override
public Promise<V> setSuccess(V result) {
if (setSuccess0(result)) {
return this;
}
throw new IllegalStateException("complete already: " + this);
}
@Override
public boolean trySuccess(V result) {
return setSuccess0(result);
}
@Override
public Promise<V> setFailure(Throwable cause) {
if (setFailure0(cause)) {
return this;
}
throw new IllegalStateException("complete already: " + this, cause);
}
@Override
public boolean tryFailure(Throwable cause) {
return setFailure0(cause);
}
@Override
public boolean setUncancellable() {
if (RESULT_UPDATER.compareAndSet(this, null, UNCANCELLABLE)) {
return true;
}
Object result = this.result;
return !isDone0(result) || !isCancelled0(result);
}
@Override
public boolean isSuccess() {
Object result = this.result;
return result != null && result != UNCANCELLABLE && !(result instanceof CauseHolder);
}
@Override
public boolean isCancellable() {
return result == null;
}
private static final class LeanCancellationException extends CancellationException {
private static final long serialVersionUID = 2794674970981187807L;
// Suppress a warning since the method doesn't need synchronization
@Override
public Throwable fillInStackTrace() {
setStackTrace(CANCELLATION_STACK);
return this;
}
@Override
public String toString() {
return CancellationException.class.getName();
}
}
@Override
public Throwable cause() {
return cause0(result);
}
private Throwable cause0(Object result) {
if (!(result instanceof CauseHolder)) {
return null;
}
if (result == CANCELLATION_CAUSE_HOLDER) {
CancellationException ce = new LeanCancellationException();
if (RESULT_UPDATER.compareAndSet(this, CANCELLATION_CAUSE_HOLDER, new CauseHolder(ce))) {
return ce;
}
result = this.result;
}
return ((CauseHolder) result).cause;
}
@Override
public Promise<V> addListener(GenericFutureListener<? extends Future<? super V>> listener) {
checkNotNull(listener, "listener");
synchronized (this) {
addListener0(listener);
}
if (isDone()) {
notifyListeners();
}
return this;
}
@Override
public Promise<V> addListeners(GenericFutureListener<? extends Future<? super V>>... listeners) {
checkNotNull(listeners, "listeners");
synchronized (this) {
for (GenericFutureListener<? extends Future<? super V>> listener : listeners) {
if (listener == null) {
break;
}
addListener0(listener);
}
}
if (isDone()) {
notifyListeners();
}
return this;
}
@Override
public Promise<V> removeListener(final GenericFutureListener<? extends Future<? super V>> listener) {
checkNotNull(listener, "listener");
synchronized (this) {
removeListener0(listener);
}
return this;
}
@Override
public Promise<V> removeListeners(final GenericFutureListener<? extends Future<? super V>>... listeners) {
checkNotNull(listeners, "listeners");
synchronized (this) {
for (GenericFutureListener<? extends Future<? super V>> listener : listeners) {
if (listener == null) {
break;
}
removeListener0(listener);
}
}
return this;
}
@Override
public Promise<V> await() throws InterruptedException {
if (isDone()) {
return this;
}
if (Thread.interrupted()) {
throw new InterruptedException(toString());
}
checkDeadLock();
synchronized (this) {
while (!isDone()) {
incWaiters();
try {
wait();
} finally {
decWaiters();
}
}
}
return this;
}
@Override
public Promise<V> awaitUninterruptibly() {
if (isDone()) {
return this;
}
checkDeadLock();
boolean interrupted = false;
synchronized (this) {
while (!isDone()) {
incWaiters();
try {
wait();
} catch (InterruptedException e) {
// Interrupted while waiting.
interrupted = true;
} finally {
decWaiters();
}
}
}
if (interrupted) {
Thread.currentThread().interrupt();
}
return this;
}
@Override
public boolean await(long timeout, TimeUnit unit) throws InterruptedException {
return await0(unit.toNanos(timeout), true);
}
@Override
public boolean await(long timeoutMillis) throws InterruptedException {
return await0(MILLISECONDS.toNanos(timeoutMillis), true);
}
@Override
public boolean awaitUninterruptibly(long timeout, TimeUnit unit) {
try {
return await0(unit.toNanos(timeout), false);
} catch (InterruptedException e) {
// Should not be raised at all.
throw new InternalError();
}
}
@Override
public boolean awaitUninterruptibly(long timeoutMillis) {
try {
return await0(MILLISECONDS.toNanos(timeoutMillis), false);
} catch (InterruptedException e) {
// Should not be raised at all.
throw new InternalError();
}
}
@SuppressWarnings("unchecked")
@Override
public V getNow() {
Object result = this.result;
if (result instanceof CauseHolder || result == SUCCESS || result == UNCANCELLABLE) {
return null;
}
return (V) result;
}
@SuppressWarnings("unchecked")
@Override
public V get() throws InterruptedException, ExecutionException {
Object result = this.result;
if (!isDone0(result)) {
await();
result = this.result;
}
if (result == SUCCESS || result == UNCANCELLABLE) {
return null;
}
Throwable cause = cause0(result);
if (cause == null) {
return (V) result;
}
if (cause instanceof CancellationException) {
throw (CancellationException) cause;
}
throw new ExecutionException(cause);
}
@SuppressWarnings("unchecked")
@Override
public V get(long timeout, TimeUnit unit) throws InterruptedException, ExecutionException, TimeoutException {
Object result = this.result;
if (!isDone0(result)) {
if (!await(timeout, unit)) {
throw new TimeoutException();
}
result = this.result;
}
if (result == SUCCESS || result == UNCANCELLABLE) {
return null;
}
Throwable cause = cause0(result);
if (cause == null) {
return (V) result;
}
if (cause instanceof CancellationException) {
throw (CancellationException) cause;
}
throw new ExecutionException(cause);
}
/**
* {@inheritDoc}
*
* @param mayInterruptIfRunning this value has no effect in this implementation.
*/
@Override
public boolean cancel(boolean mayInterruptIfRunning) {
if (RESULT_UPDATER.compareAndSet(this, null, CANCELLATION_CAUSE_HOLDER)) {
if (checkNotifyWaiters()) {
notifyListeners();
}
return true;
}
return false;
}
@Override
public boolean isCancelled() {
return isCancelled0(result);
}
@Override
public boolean isDone() {
return isDone0(result);
}
@Override
public Promise<V> sync() throws InterruptedException {
await();
rethrowIfFailed();
return this;
}
@Override
public Promise<V> syncUninterruptibly() {
awaitUninterruptibly();
rethrowIfFailed();
return this;
}
@Override
public String toString() {
return toStringBuilder().toString();
}
protected StringBuilder toStringBuilder() {
StringBuilder buf = new StringBuilder(64)
.append(StringUtil.simpleClassName(this))
.append('@')
.append(Integer.toHexString(hashCode()));
Object result = this.result;
if (result == SUCCESS) {
buf.append("(success)");
} else if (result == UNCANCELLABLE) {
buf.append("(uncancellable)");
} else if (result instanceof CauseHolder) {
buf.append("(failure: ")
.append(((CauseHolder) result).cause)
.append(')');
} else if (result != null) {
buf.append("(success: ")
.append(result)
.append(')');
} else {
buf.append("(incomplete)");
}
return buf;
}
/**
* Get the executor used to notify listeners when this promise is complete.
* <p>
* It is assumed this executor will protect against {@link StackOverflowError} exceptions.
* The executor may be used to avoid {@link StackOverflowError} by executing a {@link Runnable} if the stack
* depth exceeds a threshold.
* @return The executor used to notify listeners when this promise is complete.
*/
protected EventExecutor executor() {
return executor;
}
protected void checkDeadLock() {
EventExecutor e = executor();
if (e != null && e.inEventLoop()) {
throw new BlockingOperationException(toString());
}
}
/**
* Notify a listener that a future has completed.
* <p>
* This method has a fixed depth of {@link #MAX_LISTENER_STACK_DEPTH} that will limit recursion to prevent
* {@link StackOverflowError} and will stop notifying listeners added after this threshold is exceeded.
* @param eventExecutor the executor to use to notify the listener {@code listener}.
* @param future the future that is complete.
* @param listener the listener to notify.
*/
protected static void notifyListener(
EventExecutor eventExecutor, final Future<?> future, final GenericFutureListener<?> listener) {
notifyListenerWithStackOverFlowProtection(
checkNotNull(eventExecutor, "eventExecutor"),
checkNotNull(future, "future"),
checkNotNull(listener, "listener"));
}
private void notifyListeners() {
EventExecutor executor = executor();
if (executor.inEventLoop()) {
final InternalThreadLocalMap threadLocals = InternalThreadLocalMap.get();
final int stackDepth = threadLocals.futureListenerStackDepth();
if (stackDepth < MAX_LISTENER_STACK_DEPTH) {
threadLocals.setFutureListenerStackDepth(stackDepth + 1);
try {
notifyListenersNow();
} finally {
threadLocals.setFutureListenerStackDepth(stackDepth);
}
return;
}
}
safeExecute(executor, new Runnable() {
@Override
public void run() {
notifyListenersNow();
}
});
}
/**
* The logic in this method should be identical to {@link #notifyListeners()} but
* cannot share code because the listener(s) cannot be cached for an instance of {@link DefaultPromise} since the
* listener(s) may be changed and is protected by a synchronized operation.
*/
private static void notifyListenerWithStackOverFlowProtection(final EventExecutor executor,
final Future<?> future,
final GenericFutureListener<?> listener) {
if (executor.inEventLoop()) {
final InternalThreadLocalMap threadLocals = InternalThreadLocalMap.get();
final int stackDepth = threadLocals.futureListenerStackDepth();
if (stackDepth < MAX_LISTENER_STACK_DEPTH) {
threadLocals.setFutureListenerStackDepth(stackDepth + 1);
try {
notifyListener0(future, listener);
} finally {
threadLocals.setFutureListenerStackDepth(stackDepth);
}
return;
}
}
safeExecute(executor, new Runnable() {
@Override
public void run() {
notifyListener0(future, listener);
}
});
}
private void notifyListenersNow() {
GenericFutureListener listener;
DefaultFutureListeners listeners;
synchronized (this) {
listener = this.listener;
listeners = this.listeners;
// Only proceed if there are listeners to notify and we are not already notifying listeners.
if (notifyingListeners || (listener == null && listeners == null)) {
return;
}
notifyingListeners = true;
if (listener != null) {
this.listener = null;
} else {
this.listeners = null;
}
}
for (;;) {
if (listener != null) {
notifyListener0(this, listener);
} else {
notifyListeners0(listeners);
}
synchronized (this) {
if (this.listener == null && this.listeners == null) {
// Nothing can throw from within this method, so setting notifyingListeners back to false does not
// need to be in a finally block.
notifyingListeners = false;
return;
}
listener = this.listener;
listeners = this.listeners;
if (listener != null) {
this.listener = null;
} else {
this.listeners = null;
}
}
}
}
private void notifyListeners0(DefaultFutureListeners listeners) {
GenericFutureListener<?>[] a = listeners.listeners();
int size = listeners.size();
for (int i = 0; i < size; i ++) {
notifyListener0(this, a[i]);
}
}
@SuppressWarnings({ "unchecked", "rawtypes" })
private static void notifyListener0(Future future, GenericFutureListener l) {
try {
l.operationComplete(future);
} catch (Throwable t) {
if (logger.isWarnEnabled()) {
logger.warn("An exception was thrown by " + l.getClass().getName() + ".operationComplete()", t);
}
}
}
private void addListener0(GenericFutureListener<? extends Future<? super V>> listener) {
if (this.listener == null) {
if (listeners == null) {
this.listener = listener;
} else {
listeners.add(listener);
}
} else {
assert listeners == null;
listeners = new DefaultFutureListeners(this.listener, listener);
this.listener = null;
}
}
private void removeListener0(GenericFutureListener<? extends Future<? super V>> toRemove) {
if (listener == toRemove) {
listener = null;
} else if (listeners != null) {
listeners.remove(toRemove);
// Removal is rare, no need for compaction
if (listeners.size() == 0) {
listeners = null;
}
}
}
private boolean setSuccess0(V result) {
return setValue0(result == null ? SUCCESS : result);
}
private boolean setFailure0(Throwable cause) {
return setValue0(new CauseHolder(checkNotNull(cause, "cause")));
}
private boolean setValue0(Object objResult) {
if (RESULT_UPDATER.compareAndSet(this, null, objResult) ||
RESULT_UPDATER.compareAndSet(this, UNCANCELLABLE, objResult)) {
if (checkNotifyWaiters()) {
notifyListeners();
}
return true;
}
return false;
}
/**
* Check if there are any waiters and if so notify these.
* @return {@code true} if there are any listeners attached to the promise, {@code false} otherwise.
*/
private synchronized boolean checkNotifyWaiters() {
if (waiters > 0) {
notifyAll();
}
return listener != null || listeners != null;
}
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;
}
PlatformDependent.throwException(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();
}
}
}
}
/**
* Notify all progressive listeners.
* <p>
* No attempt is made to ensure notification order if multiple calls are made to this method before
* the original invocation completes.
* <p>
* This will do an iteration over all listeners to get all of type {@link GenericProgressiveFutureListener}s.
* @param progress the new progress.
* @param total the total progress.
*/
@SuppressWarnings("unchecked")
void notifyProgressiveListeners(final long progress, final long total) {
final Object listeners = progressiveListeners();
if (listeners == null) {
return;
}
final ProgressiveFuture<V> self = (ProgressiveFuture<V>) this;
EventExecutor executor = executor();
if (executor.inEventLoop()) {
if (listeners instanceof GenericProgressiveFutureListener[]) {
notifyProgressiveListeners0(
self, (GenericProgressiveFutureListener<?>[]) listeners, progress, total);
} else {
notifyProgressiveListener0(
self, (GenericProgressiveFutureListener<ProgressiveFuture<V>>) listeners, progress, total);
}
} else {
if (listeners instanceof GenericProgressiveFutureListener[]) {
final GenericProgressiveFutureListener<?>[] array =
(GenericProgressiveFutureListener<?>[]) listeners;
safeExecute(executor, new Runnable() {
@Override
public void run() {
notifyProgressiveListeners0(self, array, progress, total);
}
});
} else {
final GenericProgressiveFutureListener<ProgressiveFuture<V>> l =
(GenericProgressiveFutureListener<ProgressiveFuture<V>>) listeners;
safeExecute(executor, new Runnable() {
@Override
public void run() {
notifyProgressiveListener0(self, l, progress, total);
}
});
}
}
}
/**
* Returns a {@link GenericProgressiveFutureListener}, an array of {@link GenericProgressiveFutureListener}, or
* {@code null}.
*/
private synchronized Object progressiveListeners() {
final GenericFutureListener listener = this.listener;
final DefaultFutureListeners listeners = this.listeners;
if (listener == null && listeners == null) {
// No listeners added
return null;
}
if (listeners != null) {
// Copy DefaultFutureListeners into an array of listeners.
DefaultFutureListeners dfl = listeners;
int progressiveSize = dfl.progressiveSize();
switch (progressiveSize) {
case 0:
return null;
case 1:
for (GenericFutureListener<?> l: dfl.listeners()) {
if (l instanceof GenericProgressiveFutureListener) {
return l;
}
}
return null;
}
GenericFutureListener<?>[] array = dfl.listeners();
GenericProgressiveFutureListener<?>[] copy = new GenericProgressiveFutureListener[progressiveSize];
for (int i = 0, j = 0; j < progressiveSize; i ++) {
GenericFutureListener<?> l = array[i];
if (l instanceof GenericProgressiveFutureListener) {
copy[j ++] = (GenericProgressiveFutureListener<?>) l;
}
}
return copy;
} else if (listener instanceof GenericProgressiveFutureListener) {
return listener;
} else {
// Only one listener was added and it's not a progressive listener.
return null;
}
}
private static void notifyProgressiveListeners0(
ProgressiveFuture<?> future, GenericProgressiveFutureListener<?>[] listeners, long progress, long total) {
for (GenericProgressiveFutureListener<?> l: listeners) {
if (l == null) {
break;
}
notifyProgressiveListener0(future, l, progress, total);
}
}
@SuppressWarnings({ "unchecked", "rawtypes" })
private static void notifyProgressiveListener0(
ProgressiveFuture future, GenericProgressiveFutureListener l, long progress, long total) {
try {
l.operationProgressed(future, progress, total);
} catch (Throwable t) {
if (logger.isWarnEnabled()) {
logger.warn("An exception was thrown by " + l.getClass().getName() + ".operationProgressed()", t);
}
}
}
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;
}
}
private 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);
}
}
private static final class StacklessCancellationException extends CancellationException {
private static final long serialVersionUID = -2974906711413716191L;
private StacklessCancellationException() { }
// 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);
}
}
}