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/*
* Copyright (C) 2007 The Guava Authors
*
* Licensed 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 com.google.common.util.concurrent;
import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;
import static java.util.Objects.requireNonNull;
import com.google.common.annotations.GwtCompatible;
import com.google.common.annotations.GwtIncompatible;
import com.google.common.annotations.J2ktIncompatible;
import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Supplier;
import com.google.common.base.Throwables;
import com.google.common.collect.Lists;
import com.google.common.collect.Queues;
import com.google.common.util.concurrent.ForwardingListenableFuture.SimpleForwardingListenableFuture;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import com.google.errorprone.annotations.concurrent.GuardedBy;
import java.lang.reflect.InvocationTargetException;
import java.util.Collection;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.Callable;
import java.util.concurrent.Delayed;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Executor;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
import java.util.concurrent.RejectedExecutionException;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.ScheduledFuture;
import java.util.concurrent.ScheduledThreadPoolExecutor;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
import org.checkerframework.checker.nullness.qual.Nullable;
/**
* Factory and utility methods for {@link java.util.concurrent.Executor}, {@link ExecutorService},
* and {@link java.util.concurrent.ThreadFactory}.
*
* @author Eric Fellheimer
* @author Kyle Littlefield
* @author Justin Mahoney
* @since 3.0
*/
@GwtCompatible(emulated = true)
@ElementTypesAreNonnullByDefault
public final class MoreExecutors {
private MoreExecutors() {}
/**
* Converts the given ThreadPoolExecutor into an ExecutorService that exits when the application
* is complete. It does so by using daemon threads and adding a shutdown hook to wait for their
* completion.
*
* This is mainly for fixed thread pools. See {@link Executors#newFixedThreadPool(int)}.
*
* @param executor the executor to modify to make sure it exits when the application is finished
* @param terminationTimeout how long to wait for the executor to finish before terminating the
* JVM
* @param timeUnit unit of time for the time parameter
* @return an unmodifiable version of the input which will not hang the JVM
*/
@J2ktIncompatible
@GwtIncompatible // TODO
@SuppressWarnings("GoodTime") // should accept a java.time.Duration
public static ExecutorService getExitingExecutorService(
ThreadPoolExecutor executor, long terminationTimeout, TimeUnit timeUnit) {
return new Application().getExitingExecutorService(executor, terminationTimeout, timeUnit);
}
/**
* Converts the given ThreadPoolExecutor into an ExecutorService that exits when the application
* is complete. It does so by using daemon threads and adding a shutdown hook to wait for their
* completion.
*
*
This method waits 120 seconds before continuing with JVM termination, even if the executor
* has not finished its work.
*
*
This is mainly for fixed thread pools. See {@link Executors#newFixedThreadPool(int)}.
*
* @param executor the executor to modify to make sure it exits when the application is finished
* @return an unmodifiable version of the input which will not hang the JVM
*/
@J2ktIncompatible
@GwtIncompatible // concurrency
public static ExecutorService getExitingExecutorService(ThreadPoolExecutor executor) {
return new Application().getExitingExecutorService(executor);
}
/**
* Converts the given ScheduledThreadPoolExecutor into a ScheduledExecutorService that exits when
* the application is complete. It does so by using daemon threads and adding a shutdown hook to
* wait for their completion.
*
*
This is mainly for fixed thread pools. See {@link Executors#newScheduledThreadPool(int)}.
*
* @param executor the executor to modify to make sure it exits when the application is finished
* @param terminationTimeout how long to wait for the executor to finish before terminating the
* JVM
* @param timeUnit unit of time for the time parameter
* @return an unmodifiable version of the input which will not hang the JVM
*/
@J2ktIncompatible
@GwtIncompatible // TODO
@SuppressWarnings("GoodTime") // should accept a java.time.Duration
public static ScheduledExecutorService getExitingScheduledExecutorService(
ScheduledThreadPoolExecutor executor, long terminationTimeout, TimeUnit timeUnit) {
return new Application()
.getExitingScheduledExecutorService(executor, terminationTimeout, timeUnit);
}
/**
* Converts the given ScheduledThreadPoolExecutor into a ScheduledExecutorService that exits when
* the application is complete. It does so by using daemon threads and adding a shutdown hook to
* wait for their completion.
*
*
This method waits 120 seconds before continuing with JVM termination, even if the executor
* has not finished its work.
*
*
This is mainly for fixed thread pools. See {@link Executors#newScheduledThreadPool(int)}.
*
* @param executor the executor to modify to make sure it exits when the application is finished
* @return an unmodifiable version of the input which will not hang the JVM
*/
@J2ktIncompatible
@GwtIncompatible // TODO
public static ScheduledExecutorService getExitingScheduledExecutorService(
ScheduledThreadPoolExecutor executor) {
return new Application().getExitingScheduledExecutorService(executor);
}
/**
* Add a shutdown hook to wait for thread completion in the given {@link ExecutorService service}.
* This is useful if the given service uses daemon threads, and we want to keep the JVM from
* exiting immediately on shutdown, instead giving these daemon threads a chance to terminate
* normally.
*
* @param service ExecutorService which uses daemon threads
* @param terminationTimeout how long to wait for the executor to finish before terminating the
* JVM
* @param timeUnit unit of time for the time parameter
*/
@J2ktIncompatible
@GwtIncompatible // TODO
@SuppressWarnings("GoodTime") // should accept a java.time.Duration
public static void addDelayedShutdownHook(
ExecutorService service, long terminationTimeout, TimeUnit timeUnit) {
new Application().addDelayedShutdownHook(service, terminationTimeout, timeUnit);
}
/** Represents the current application to register shutdown hooks. */
@J2ktIncompatible
@GwtIncompatible // TODO
@VisibleForTesting
static class Application {
final ExecutorService getExitingExecutorService(
ThreadPoolExecutor executor, long terminationTimeout, TimeUnit timeUnit) {
useDaemonThreadFactory(executor);
ExecutorService service = Executors.unconfigurableExecutorService(executor);
addDelayedShutdownHook(executor, terminationTimeout, timeUnit);
return service;
}
final ExecutorService getExitingExecutorService(ThreadPoolExecutor executor) {
return getExitingExecutorService(executor, 120, TimeUnit.SECONDS);
}
final ScheduledExecutorService getExitingScheduledExecutorService(
ScheduledThreadPoolExecutor executor, long terminationTimeout, TimeUnit timeUnit) {
useDaemonThreadFactory(executor);
ScheduledExecutorService service = Executors.unconfigurableScheduledExecutorService(executor);
addDelayedShutdownHook(executor, terminationTimeout, timeUnit);
return service;
}
final ScheduledExecutorService getExitingScheduledExecutorService(
ScheduledThreadPoolExecutor executor) {
return getExitingScheduledExecutorService(executor, 120, TimeUnit.SECONDS);
}
final void addDelayedShutdownHook(
final ExecutorService service, final long terminationTimeout, final TimeUnit timeUnit) {
checkNotNull(service);
checkNotNull(timeUnit);
addShutdownHook(
MoreExecutors.newThread(
"DelayedShutdownHook-for-" + service,
new Runnable() {
@Override
public void run() {
try {
// We'd like to log progress and failures that may arise in the
// following code, but unfortunately the behavior of logging
// is undefined in shutdown hooks.
// This is because the logging code installs a shutdown hook of its
// own. See Cleaner class inside {@link LogManager}.
service.shutdown();
service.awaitTermination(terminationTimeout, timeUnit);
} catch (InterruptedException ignored) {
// We're shutting down anyway, so just ignore.
}
}
}));
}
@VisibleForTesting
void addShutdownHook(Thread hook) {
Runtime.getRuntime().addShutdownHook(hook);
}
}
@J2ktIncompatible
@GwtIncompatible // TODO
private static void useDaemonThreadFactory(ThreadPoolExecutor executor) {
executor.setThreadFactory(
new ThreadFactoryBuilder()
.setDaemon(true)
.setThreadFactory(executor.getThreadFactory())
.build());
}
// See newDirectExecutorService javadoc for behavioral notes.
@J2ktIncompatible
@GwtIncompatible // TODO
private static final class DirectExecutorService extends AbstractListeningExecutorService {
/** Lock used whenever accessing the state variables (runningTasks, shutdown) of the executor */
private final Object lock = new Object();
/*
* Conceptually, these two variables describe the executor being in
* one of three states:
* - Active: shutdown == false
* - Shutdown: runningTasks > 0 and shutdown == true
* - Terminated: runningTasks == 0 and shutdown == true
*/
@GuardedBy("lock")
private int runningTasks = 0;
@GuardedBy("lock")
private boolean shutdown = false;
@Override
public void execute(Runnable command) {
startTask();
try {
command.run();
} finally {
endTask();
}
}
@Override
public boolean isShutdown() {
synchronized (lock) {
return shutdown;
}
}
@Override
public void shutdown() {
synchronized (lock) {
shutdown = true;
if (runningTasks == 0) {
lock.notifyAll();
}
}
}
// See newDirectExecutorService javadoc for unusual behavior of this method.
@Override
public List shutdownNow() {
shutdown();
return Collections.emptyList();
}
@Override
public boolean isTerminated() {
synchronized (lock) {
return shutdown && runningTasks == 0;
}
}
@Override
public boolean awaitTermination(long timeout, TimeUnit unit) throws InterruptedException {
long nanos = unit.toNanos(timeout);
synchronized (lock) {
while (true) {
if (shutdown && runningTasks == 0) {
return true;
} else if (nanos <= 0) {
return false;
} else {
long now = System.nanoTime();
TimeUnit.NANOSECONDS.timedWait(lock, nanos);
nanos -= System.nanoTime() - now; // subtract the actual time we waited
}
}
}
}
/**
* Checks if the executor has been shut down and increments the running task count.
*
* @throws RejectedExecutionException if the executor has been previously shutdown
*/
private void startTask() {
synchronized (lock) {
if (shutdown) {
throw new RejectedExecutionException("Executor already shutdown");
}
runningTasks++;
}
}
/** Decrements the running task count. */
private void endTask() {
synchronized (lock) {
int numRunning = --runningTasks;
if (numRunning == 0) {
lock.notifyAll();
}
}
}
}
/**
* Creates an executor service that runs each task in the thread that invokes {@code
* execute/submit}, as in {@code ThreadPoolExecutor.CallerRunsPolicy}. This applies both to
* individually submitted tasks and to collections of tasks submitted via {@code invokeAll} or
* {@code invokeAny}. In the latter case, tasks will run serially on the calling thread. Tasks are
* run to completion before a {@code Future} is returned to the caller (unless the executor has
* been shutdown).
*
* Although all tasks are immediately executed in the thread that submitted the task, this
* {@code ExecutorService} imposes a small locking overhead on each task submission in order to
* implement shutdown and termination behavior.
*
*
The implementation deviates from the {@code ExecutorService} specification with regards to
* the {@code shutdownNow} method. First, "best-effort" with regards to canceling running tasks is
* implemented as "no-effort". No interrupts or other attempts are made to stop threads executing
* tasks. Second, the returned list will always be empty, as any submitted task is considered to
* have started execution. This applies also to tasks given to {@code invokeAll} or {@code
* invokeAny} which are pending serial execution, even the subset of the tasks that have not yet
* started execution. It is unclear from the {@code ExecutorService} specification if these should
* be included, and it's much easier to implement the interpretation that they not be. Finally, a
* call to {@code shutdown} or {@code shutdownNow} may result in concurrent calls to {@code
* invokeAll/invokeAny} throwing RejectedExecutionException, although a subset of the tasks may
* already have been executed.
*
* @since 18.0 (present as MoreExecutors.sameThreadExecutor() since 10.0)
*/
@J2ktIncompatible
@GwtIncompatible // TODO
public static ListeningExecutorService newDirectExecutorService() {
return new DirectExecutorService();
}
/**
* Returns an {@link Executor} that runs each task in the thread that invokes {@link
* Executor#execute execute}, as in {@code ThreadPoolExecutor.CallerRunsPolicy}.
*
*
This executor is appropriate for tasks that are lightweight and not deeply chained.
* Inappropriate {@code directExecutor} usage can cause problems, and these problems can be
* difficult to reproduce because they depend on timing. For example:
*
*
* - When a {@code ListenableFuture} listener is registered to run under {@code
* directExecutor}, the listener can execute in any of three possible threads:
*
* - When a thread attaches a listener to a {@code ListenableFuture} that's already
* complete, the listener runs immediately in that thread.
*
- When a thread attaches a listener to a {@code ListenableFuture} that's
* incomplete and the {@code ListenableFuture} later completes normally, the
* listener runs in the thread that completes the {@code ListenableFuture}.
*
- When a listener is attached to a {@code ListenableFuture} and the {@code
* ListenableFuture} gets cancelled, the listener runs immediately in the thread that
* cancelled the {@code Future}.
*
* Given all these possibilities, it is frequently possible for listeners to execute in UI
* threads, RPC network threads, or other latency-sensitive threads. In those cases, slow
* listeners can harm responsiveness, slow the system as a whole, or worse. (See also the
* note about locking below.)
* - If many tasks will be triggered by the same event, one heavyweight task may delay other
* tasks -- even tasks that are not themselves {@code directExecutor} tasks.
*
- If many such tasks are chained together (such as with {@code
* future.transform(...).transform(...).transform(...)....}), they may overflow the stack.
* (In simple cases, callers can avoid this by registering all tasks with the same {@link
* MoreExecutors#newSequentialExecutor} wrapper around {@code directExecutor()}. More
* complex cases may require using thread pools or making deeper changes.)
*
- If an exception propagates out of a {@code Runnable}, it is not necessarily seen by any
* {@code UncaughtExceptionHandler} for the thread. For example, if the callback passed to
* {@link Futures#addCallback} throws an exception, that exception will be typically be
* logged by the {@link ListenableFuture} implementation, even if the thread is configured
* to do something different. In other cases, no code will catch the exception, and it may
* terminate whichever thread happens to trigger the execution.
*
*
* A specific warning about locking: Code that executes user-supplied tasks, such as {@code
* ListenableFuture} listeners, should take care not to do so while holding a lock. Additionally,
* as a further line of defense, prefer not to perform any locking inside a task that will be run
* under {@code directExecutor}: Not only might the wait for a lock be long, but if the running
* thread was holding a lock, the listener may deadlock or break lock isolation.
*
* This instance is equivalent to:
*
*
{@code
* final class DirectExecutor implements Executor {
* public void execute(Runnable r) {
* r.run();
* }
* }
* }
*
* This should be preferred to {@link #newDirectExecutorService()} because implementing the
* {@link ExecutorService} subinterface necessitates significant performance overhead.
*
* @since 18.0
*/
public static Executor directExecutor() {
return DirectExecutor.INSTANCE;
}
/**
* Returns an {@link Executor} that runs each task executed sequentially, such that no two tasks
* are running concurrently.
*
*
{@linkplain Executor#execute executed} tasks have a happens-before order as defined in the
* Java Language Specification. Tasks execute with the same happens-before order that the function
* calls to {@link Executor#execute `execute()`} that submitted those tasks had.
*
*
The executor uses {@code delegate} in order to {@link Executor#execute execute} each task in
* turn, and does not create any threads of its own.
*
*
After execution begins on a thread from the {@code delegate} {@link Executor}, tasks are
* polled and executed from a task queue until there are no more tasks. The thread will not be
* released until there are no more tasks to run.
*
*
If a task is submitted while a thread is executing tasks from the task queue, the thread
* will not be released until that submitted task is also complete.
*
*
If a task is {@linkplain Thread#interrupt interrupted} while a task is running:
*
*
* - execution will not stop until the task queue is empty.
*
- tasks will begin execution with the thread marked as not interrupted - any interruption
* applies only to the task that was running at the point of interruption.
*
- if the thread was interrupted before the SequentialExecutor's worker begins execution,
* the interrupt will be restored to the thread after it completes so that its {@code
* delegate} Executor may process the interrupt.
*
- subtasks are run with the thread uninterrupted and interrupts received during execution
* of a task are ignored.
*
*
* {@code RuntimeException}s thrown by tasks are simply logged and the executor keeps trucking.
* If an {@code Error} is thrown, the error will propagate and execution will stop until the next
* time a task is submitted.
*
*
When an {@code Error} is thrown by an executed task, previously submitted tasks may never
* run. An attempt will be made to restart execution on the next call to {@code execute}. If the
* {@code delegate} has begun to reject execution, the previously submitted tasks may never run,
* despite not throwing a RejectedExecutionException synchronously with the call to {@code
* execute}. If this behaviour is problematic, use an Executor with a single thread (e.g. {@link
* Executors#newSingleThreadExecutor}).
*
* @since 23.3 (since 23.1 as {@code sequentialExecutor})
*/
@J2ktIncompatible
@GwtIncompatible
public static Executor newSequentialExecutor(Executor delegate) {
return new SequentialExecutor(delegate);
}
/**
* Creates an {@link ExecutorService} whose {@code submit} and {@code invokeAll} methods submit
* {@link ListenableFutureTask} instances to the given delegate executor. Those methods, as well
* as {@code execute} and {@code invokeAny}, are implemented in terms of calls to {@code
* delegate.execute}. All other methods are forwarded unchanged to the delegate. This implies that
* the returned {@code ListeningExecutorService} never calls the delegate's {@code submit}, {@code
* invokeAll}, and {@code invokeAny} methods, so any special handling of tasks must be implemented
* in the delegate's {@code execute} method or by wrapping the returned {@code
* ListeningExecutorService}.
*
*
If the delegate executor was already an instance of {@code ListeningExecutorService}, it is
* returned untouched, and the rest of this documentation does not apply.
*
* @since 10.0
*/
@J2ktIncompatible
@GwtIncompatible // TODO
public static ListeningExecutorService listeningDecorator(ExecutorService delegate) {
return (delegate instanceof ListeningExecutorService)
? (ListeningExecutorService) delegate
: (delegate instanceof ScheduledExecutorService)
? new ScheduledListeningDecorator((ScheduledExecutorService) delegate)
: new ListeningDecorator(delegate);
}
/**
* Creates a {@link ScheduledExecutorService} whose {@code submit} and {@code invokeAll} methods
* submit {@link ListenableFutureTask} instances to the given delegate executor. Those methods, as
* well as {@code execute} and {@code invokeAny}, are implemented in terms of calls to {@code
* delegate.execute}. All other methods are forwarded unchanged to the delegate. This implies that
* the returned {@code ListeningScheduledExecutorService} never calls the delegate's {@code
* submit}, {@code invokeAll}, and {@code invokeAny} methods, so any special handling of tasks
* must be implemented in the delegate's {@code execute} method or by wrapping the returned {@code
* ListeningScheduledExecutorService}.
*
*
If the delegate executor was already an instance of {@code
* ListeningScheduledExecutorService}, it is returned untouched, and the rest of this
* documentation does not apply.
*
* @since 10.0
*/
@J2ktIncompatible
@GwtIncompatible // TODO
public static ListeningScheduledExecutorService listeningDecorator(
ScheduledExecutorService delegate) {
return (delegate instanceof ListeningScheduledExecutorService)
? (ListeningScheduledExecutorService) delegate
: new ScheduledListeningDecorator(delegate);
}
@J2ktIncompatible
@GwtIncompatible // TODO
private static class ListeningDecorator extends AbstractListeningExecutorService {
private final ExecutorService delegate;
ListeningDecorator(ExecutorService delegate) {
this.delegate = checkNotNull(delegate);
}
@Override
public final boolean awaitTermination(long timeout, TimeUnit unit) throws InterruptedException {
return delegate.awaitTermination(timeout, unit);
}
@Override
public final boolean isShutdown() {
return delegate.isShutdown();
}
@Override
public final boolean isTerminated() {
return delegate.isTerminated();
}
@Override
public final void shutdown() {
delegate.shutdown();
}
@Override
public final List shutdownNow() {
return delegate.shutdownNow();
}
@Override
public final void execute(Runnable command) {
delegate.execute(command);
}
@Override
public final String toString() {
return super.toString() + "[" + delegate + "]";
}
}
@J2ktIncompatible
@GwtIncompatible // TODO
private static final class ScheduledListeningDecorator extends ListeningDecorator
implements ListeningScheduledExecutorService {
@SuppressWarnings("hiding")
final ScheduledExecutorService delegate;
ScheduledListeningDecorator(ScheduledExecutorService delegate) {
super(delegate);
this.delegate = checkNotNull(delegate);
}
@Override
public ListenableScheduledFuture schedule(Runnable command, long delay, TimeUnit unit) {
TrustedListenableFutureTask<@Nullable Void> task =
TrustedListenableFutureTask.create(command, null);
ScheduledFuture scheduled = delegate.schedule(task, delay, unit);
return new ListenableScheduledTask<@Nullable Void>(task, scheduled);
}
@Override
public ListenableScheduledFuture schedule(
Callable callable, long delay, TimeUnit unit) {
TrustedListenableFutureTask task = TrustedListenableFutureTask.create(callable);
ScheduledFuture scheduled = delegate.schedule(task, delay, unit);
return new ListenableScheduledTask(task, scheduled);
}
@Override
public ListenableScheduledFuture scheduleAtFixedRate(
Runnable command, long initialDelay, long period, TimeUnit unit) {
NeverSuccessfulListenableFutureTask task = new NeverSuccessfulListenableFutureTask(command);
ScheduledFuture scheduled = delegate.scheduleAtFixedRate(task, initialDelay, period, unit);
return new ListenableScheduledTask<@Nullable Void>(task, scheduled);
}
@Override
public ListenableScheduledFuture scheduleWithFixedDelay(
Runnable command, long initialDelay, long delay, TimeUnit unit) {
NeverSuccessfulListenableFutureTask task = new NeverSuccessfulListenableFutureTask(command);
ScheduledFuture scheduled =
delegate.scheduleWithFixedDelay(task, initialDelay, delay, unit);
return new ListenableScheduledTask<@Nullable Void>(task, scheduled);
}
private static final class ListenableScheduledTask
extends SimpleForwardingListenableFuture implements ListenableScheduledFuture {
private final ScheduledFuture scheduledDelegate;
public ListenableScheduledTask(
ListenableFuture listenableDelegate, ScheduledFuture scheduledDelegate) {
super(listenableDelegate);
this.scheduledDelegate = scheduledDelegate;
}
@Override
public boolean cancel(boolean mayInterruptIfRunning) {
boolean cancelled = super.cancel(mayInterruptIfRunning);
if (cancelled) {
// Unless it is cancelled, the delegate may continue being scheduled
scheduledDelegate.cancel(mayInterruptIfRunning);
// TODO(user): Cancel "this" if "scheduledDelegate" is cancelled.
}
return cancelled;
}
@Override
public long getDelay(TimeUnit unit) {
return scheduledDelegate.getDelay(unit);
}
@Override
public int compareTo(Delayed other) {
return scheduledDelegate.compareTo(other);
}
}
@J2ktIncompatible
@GwtIncompatible // TODO
private static final class NeverSuccessfulListenableFutureTask
extends AbstractFuture.TrustedFuture<@Nullable Void> implements Runnable {
private final Runnable delegate;
public NeverSuccessfulListenableFutureTask(Runnable delegate) {
this.delegate = checkNotNull(delegate);
}
@Override
public void run() {
try {
delegate.run();
} catch (RuntimeException | Error t) {
setException(t);
throw t;
}
}
@Override
protected String pendingToString() {
return "task=[" + delegate + "]";
}
}
}
/*
* This following method is a modified version of one found in
* http://gee.cs.oswego.edu/cgi-bin/viewcvs.cgi/jsr166/src/test/tck/AbstractExecutorServiceTest.java?revision=1.30
* which contained the following notice:
*
* Written by Doug Lea with assistance from members of JCP JSR-166 Expert Group and released to
* the public domain, as explained at http://creativecommons.org/publicdomain/zero/1.0/
*
* Other contributors include Andrew Wright, Jeffrey Hayes, Pat Fisher, Mike Judd.
*/
/**
* An implementation of {@link ExecutorService#invokeAny} for {@link ListeningExecutorService}
* implementations.
*/
@SuppressWarnings("GoodTime") // should accept a java.time.Duration
@J2ktIncompatible
@GwtIncompatible
@ParametricNullness
static T invokeAnyImpl(
ListeningExecutorService executorService,
Collection> tasks,
boolean timed,
long timeout,
TimeUnit unit)
throws InterruptedException, ExecutionException, TimeoutException {
checkNotNull(executorService);
checkNotNull(unit);
int ntasks = tasks.size();
checkArgument(ntasks > 0);
List> futures = Lists.newArrayListWithCapacity(ntasks);
BlockingQueue> futureQueue = Queues.newLinkedBlockingQueue();
long timeoutNanos = unit.toNanos(timeout);
// For efficiency, especially in executors with limited
// parallelism, check to see if previously submitted tasks are
// done before submitting more of them. This interleaving
// plus the exception mechanics account for messiness of main
// loop.
try {
// Record exceptions so that if we fail to obtain any
// result, we can throw the last exception we got.
ExecutionException ee = null;
long lastTime = timed ? System.nanoTime() : 0;
Iterator> it = tasks.iterator();
futures.add(submitAndAddQueueListener(executorService, it.next(), futureQueue));
--ntasks;
int active = 1;
while (true) {
Future f = futureQueue.poll();
if (f == null) {
if (ntasks > 0) {
--ntasks;
futures.add(submitAndAddQueueListener(executorService, it.next(), futureQueue));
++active;
} else if (active == 0) {
break;
} else if (timed) {
f = futureQueue.poll(timeoutNanos, TimeUnit.NANOSECONDS);
if (f == null) {
throw new TimeoutException();
}
long now = System.nanoTime();
timeoutNanos -= now - lastTime;
lastTime = now;
} else {
f = futureQueue.take();
}
}
if (f != null) {
--active;
try {
return f.get();
} catch (ExecutionException eex) {
ee = eex;
} catch (RuntimeException rex) {
ee = new ExecutionException(rex);
}
}
}
if (ee == null) {
ee = new ExecutionException(null);
}
throw ee;
} finally {
for (Future f : futures) {
f.cancel(true);
}
}
}
/**
* Submits the task and adds a listener that adds the future to {@code queue} when it completes.
*/
@J2ktIncompatible
@GwtIncompatible // TODO
private static ListenableFuture submitAndAddQueueListener(
ListeningExecutorService executorService,
Callable task,
final BlockingQueue> queue) {
final ListenableFuture future = executorService.submit(task);
future.addListener(
new Runnable() {
@Override
public void run() {
queue.add(future);
}
},
directExecutor());
return future;
}
/**
* Returns a default thread factory used to create new threads.
*
* When running on AppEngine with access to AppEngine legacy
* APIs, this method returns {@code ThreadManager.currentRequestThreadFactory()}. Otherwise,
* it returns {@link Executors#defaultThreadFactory()}.
*
* @since 14.0
*/
@J2ktIncompatible
@GwtIncompatible // concurrency
public static ThreadFactory platformThreadFactory() {
if (!isAppEngineWithApiClasses()) {
return Executors.defaultThreadFactory();
}
try {
return (ThreadFactory)
Class.forName("com.google.appengine.api.ThreadManager")
.getMethod("currentRequestThreadFactory")
.invoke(null);
/*
* Do not merge the 3 catch blocks below. javac would infer a type of
* ReflectiveOperationException, which Animal Sniffer would reject. (Old versions of Android
* don't *seem* to mind, but there might be edge cases of which we're unaware.)
*/
} catch (IllegalAccessException e) {
throw new RuntimeException("Couldn't invoke ThreadManager.currentRequestThreadFactory", e);
} catch (ClassNotFoundException e) {
throw new RuntimeException("Couldn't invoke ThreadManager.currentRequestThreadFactory", e);
} catch (NoSuchMethodException e) {
throw new RuntimeException("Couldn't invoke ThreadManager.currentRequestThreadFactory", e);
} catch (InvocationTargetException e) {
throw Throwables.propagate(e.getCause());
}
}
@J2ktIncompatible
@GwtIncompatible // TODO
private static boolean isAppEngineWithApiClasses() {
if (System.getProperty("com.google.appengine.runtime.environment") == null) {
return false;
}
try {
Class.forName("com.google.appengine.api.utils.SystemProperty");
} catch (ClassNotFoundException e) {
return false;
}
try {
// If the current environment is null, we're not inside AppEngine.
return Class.forName("com.google.apphosting.api.ApiProxy")
.getMethod("getCurrentEnvironment")
.invoke(null)
!= null;
} catch (ClassNotFoundException e) {
// If ApiProxy doesn't exist, we're not on AppEngine at all.
return false;
} catch (InvocationTargetException e) {
// If ApiProxy throws an exception, we're not in a proper AppEngine environment.
return false;
} catch (IllegalAccessException e) {
// If the method isn't accessible, we're not on a supported version of AppEngine;
return false;
} catch (NoSuchMethodException e) {
// If the method doesn't exist, we're not on a supported version of AppEngine;
return false;
}
}
/**
* Creates a thread using {@link #platformThreadFactory}, and sets its name to {@code name} unless
* changing the name is forbidden by the security manager.
*/
@J2ktIncompatible
@GwtIncompatible // concurrency
static Thread newThread(String name, Runnable runnable) {
checkNotNull(name);
checkNotNull(runnable);
// TODO(b/139726489): Confirm that null is impossible here.
Thread result = requireNonNull(platformThreadFactory().newThread(runnable));
try {
result.setName(name);
} catch (SecurityException e) {
// OK if we can't set the name in this environment.
}
return result;
}
// TODO(lukes): provide overloads for ListeningExecutorService? ListeningScheduledExecutorService?
// TODO(lukes): provide overloads that take constant strings? Functions to
// calculate names?
/**
* Creates an {@link Executor} that renames the {@link Thread threads} that its tasks run in.
*
* The names are retrieved from the {@code nameSupplier} on the thread that is being renamed
* right before each task is run. The renaming is best effort, if a {@link SecurityManager}
* prevents the renaming then it will be skipped but the tasks will still execute.
*
* @param executor The executor to decorate
* @param nameSupplier The source of names for each task
*/
@J2ktIncompatible
@GwtIncompatible // concurrency
static Executor renamingDecorator(final Executor executor, final Supplier nameSupplier) {
checkNotNull(executor);
checkNotNull(nameSupplier);
return new Executor() {
@Override
public void execute(Runnable command) {
executor.execute(Callables.threadRenaming(command, nameSupplier));
}
};
}
/**
* Creates an {@link ExecutorService} that renames the {@link Thread threads} that its tasks run
* in.
*
* The names are retrieved from the {@code nameSupplier} on the thread that is being renamed
* right before each task is run. The renaming is best effort, if a {@link SecurityManager}
* prevents the renaming then it will be skipped but the tasks will still execute.
*
* @param service The executor to decorate
* @param nameSupplier The source of names for each task
*/
@J2ktIncompatible
@GwtIncompatible // concurrency
static ExecutorService renamingDecorator(
final ExecutorService service, final Supplier nameSupplier) {
checkNotNull(service);
checkNotNull(nameSupplier);
return new WrappingExecutorService(service) {
@Override
protected Callable wrapTask(Callable callable) {
return Callables.threadRenaming(callable, nameSupplier);
}
@Override
protected Runnable wrapTask(Runnable command) {
return Callables.threadRenaming(command, nameSupplier);
}
};
}
/**
* Creates a {@link ScheduledExecutorService} that renames the {@link Thread threads} that its
* tasks run in.
*
* The names are retrieved from the {@code nameSupplier} on the thread that is being renamed
* right before each task is run. The renaming is best effort, if a {@link SecurityManager}
* prevents the renaming then it will be skipped but the tasks will still execute.
*
* @param service The executor to decorate
* @param nameSupplier The source of names for each task
*/
@J2ktIncompatible
@GwtIncompatible // concurrency
static ScheduledExecutorService renamingDecorator(
final ScheduledExecutorService service, final Supplier nameSupplier) {
checkNotNull(service);
checkNotNull(nameSupplier);
return new WrappingScheduledExecutorService(service) {
@Override
protected Callable wrapTask(Callable callable) {
return Callables.threadRenaming(callable, nameSupplier);
}
@Override
protected Runnable wrapTask(Runnable command) {
return Callables.threadRenaming(command, nameSupplier);
}
};
}
/**
* Shuts down the given executor service gradually, first disabling new submissions and later, if
* necessary, cancelling remaining tasks.
*
* The method takes the following steps:
*
*
* - calls {@link ExecutorService#shutdown()}, disabling acceptance of new submitted tasks.
*
- awaits executor service termination for half of the specified timeout.
*
- if the timeout expires, it calls {@link ExecutorService#shutdownNow()}, cancelling
* pending tasks and interrupting running tasks.
*
- awaits executor service termination for the other half of the specified timeout.
*
*
* If, at any step of the process, the calling thread is interrupted, the method calls {@link
* ExecutorService#shutdownNow()} and returns.
*
* @param service the {@code ExecutorService} to shut down
* @param timeout the maximum time to wait for the {@code ExecutorService} to terminate
* @param unit the time unit of the timeout argument
* @return {@code true} if the {@code ExecutorService} was terminated successfully, {@code false}
* if the call timed out or was interrupted
* @since 17.0
*/
@CanIgnoreReturnValue
@J2ktIncompatible
@GwtIncompatible // concurrency
@SuppressWarnings("GoodTime") // should accept a java.time.Duration
public static boolean shutdownAndAwaitTermination(
ExecutorService service, long timeout, TimeUnit unit) {
long halfTimeoutNanos = unit.toNanos(timeout) / 2;
// Disable new tasks from being submitted
service.shutdown();
try {
// Wait for half the duration of the timeout for existing tasks to terminate
if (!service.awaitTermination(halfTimeoutNanos, TimeUnit.NANOSECONDS)) {
// Cancel currently executing tasks
service.shutdownNow();
// Wait the other half of the timeout for tasks to respond to being cancelled
service.awaitTermination(halfTimeoutNanos, TimeUnit.NANOSECONDS);
}
} catch (InterruptedException ie) {
// Preserve interrupt status
Thread.currentThread().interrupt();
// (Re-)Cancel if current thread also interrupted
service.shutdownNow();
}
return service.isTerminated();
}
/**
* Returns an Executor that will propagate {@link RejectedExecutionException} from the delegate
* executor to the given {@code future}.
*
*
Note, the returned executor can only be used once.
*/
static Executor rejectionPropagatingExecutor(
final Executor delegate, final AbstractFuture future) {
checkNotNull(delegate);
checkNotNull(future);
if (delegate == directExecutor()) {
// directExecutor() cannot throw RejectedExecutionException
return delegate;
}
return new Executor() {
@Override
public void execute(Runnable command) {
try {
delegate.execute(command);
} catch (RejectedExecutionException e) {
future.setException(e);
}
}
};
}
}