NonStickyEventExecutorGroup.java
/*
* Copyright 2016 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.ObjectUtil;
import io.netty.util.internal.PlatformDependent;
import io.netty.util.internal.UnstableApi;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import java.util.Queue;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.RejectedExecutionException;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.atomic.AtomicReference;
/**
* {@link EventExecutorGroup} which will preserve {@link Runnable} execution order but makes no guarantees about what
* {@link EventExecutor} (and therefore {@link Thread}) will be used to execute the {@link Runnable}s.
*
* <p>The {@link EventExecutorGroup#next()} for the wrapped {@link EventExecutorGroup} must <strong>NOT</strong> return
* executors of type {@link OrderedEventExecutor}.
*/
@UnstableApi
public final class NonStickyEventExecutorGroup implements EventExecutorGroup {
private final EventExecutorGroup group;
private final int maxTaskExecutePerRun;
/**
* Creates a new instance. Be aware that the given {@link EventExecutorGroup} <strong>MUST NOT</strong> contain
* any {@link OrderedEventExecutor}s.
*/
public NonStickyEventExecutorGroup(EventExecutorGroup group) {
this(group, 1024);
}
/**
* Creates a new instance. Be aware that the given {@link EventExecutorGroup} <strong>MUST NOT</strong> contain
* any {@link OrderedEventExecutor}s.
*/
public NonStickyEventExecutorGroup(EventExecutorGroup group, int maxTaskExecutePerRun) {
this.group = verify(group);
this.maxTaskExecutePerRun = ObjectUtil.checkPositive(maxTaskExecutePerRun, "maxTaskExecutePerRun");
}
private static EventExecutorGroup verify(EventExecutorGroup group) {
Iterator<EventExecutor> executors = ObjectUtil.checkNotNull(group, "group").iterator();
while (executors.hasNext()) {
EventExecutor executor = executors.next();
if (executor instanceof OrderedEventExecutor) {
throw new IllegalArgumentException("EventExecutorGroup " + group
+ " contains OrderedEventExecutors: " + executor);
}
}
return group;
}
private NonStickyOrderedEventExecutor newExecutor(EventExecutor executor) {
return new NonStickyOrderedEventExecutor(executor, maxTaskExecutePerRun);
}
@Override
public boolean isShuttingDown() {
return group.isShuttingDown();
}
@Override
public Future<?> shutdownGracefully() {
return group.shutdownGracefully();
}
@Override
public Future<?> shutdownGracefully(long quietPeriod, long timeout, TimeUnit unit) {
return group.shutdownGracefully(quietPeriod, timeout, unit);
}
@Override
public Future<?> terminationFuture() {
return group.terminationFuture();
}
@SuppressWarnings("deprecation")
@Override
public void shutdown() {
group.shutdown();
}
@SuppressWarnings("deprecation")
@Override
public List<Runnable> shutdownNow() {
return group.shutdownNow();
}
@Override
public EventExecutor next() {
return newExecutor(group.next());
}
@Override
public Iterator<EventExecutor> iterator() {
final Iterator<EventExecutor> itr = group.iterator();
return new Iterator<EventExecutor>() {
@Override
public boolean hasNext() {
return itr.hasNext();
}
@Override
public EventExecutor next() {
return newExecutor(itr.next());
}
@Override
public void remove() {
itr.remove();
}
};
}
@Override
public Future<?> submit(Runnable task) {
return group.submit(task);
}
@Override
public <T> Future<T> submit(Runnable task, T result) {
return group.submit(task, result);
}
@Override
public <T> Future<T> submit(Callable<T> task) {
return group.submit(task);
}
@Override
public ScheduledFuture<?> schedule(Runnable command, long delay, TimeUnit unit) {
return group.schedule(command, delay, unit);
}
@Override
public <V> ScheduledFuture<V> schedule(Callable<V> callable, long delay, TimeUnit unit) {
return group.schedule(callable, delay, unit);
}
@Override
public ScheduledFuture<?> scheduleAtFixedRate(Runnable command, long initialDelay, long period, TimeUnit unit) {
return group.scheduleAtFixedRate(command, initialDelay, period, unit);
}
@Override
public ScheduledFuture<?> scheduleWithFixedDelay(Runnable command, long initialDelay, long delay, TimeUnit unit) {
return group.scheduleWithFixedDelay(command, initialDelay, delay, unit);
}
@Override
public boolean isShutdown() {
return group.isShutdown();
}
@Override
public boolean isTerminated() {
return group.isTerminated();
}
@Override
public boolean awaitTermination(long timeout, TimeUnit unit) throws InterruptedException {
return group.awaitTermination(timeout, unit);
}
@Override
public <T> List<java.util.concurrent.Future<T>> invokeAll(
Collection<? extends Callable<T>> tasks) throws InterruptedException {
return group.invokeAll(tasks);
}
@Override
public <T> List<java.util.concurrent.Future<T>> invokeAll(
Collection<? extends Callable<T>> tasks, long timeout, TimeUnit unit) throws InterruptedException {
return group.invokeAll(tasks, timeout, unit);
}
@Override
public <T> T invokeAny(Collection<? extends Callable<T>> tasks) throws InterruptedException, ExecutionException {
return group.invokeAny(tasks);
}
@Override
public <T> T invokeAny(Collection<? extends Callable<T>> tasks, long timeout, TimeUnit unit)
throws InterruptedException, ExecutionException, TimeoutException {
return group.invokeAny(tasks, timeout, unit);
}
@Override
public void execute(Runnable command) {
group.execute(command);
}
private static final class NonStickyOrderedEventExecutor extends AbstractEventExecutor
implements Runnable, OrderedEventExecutor {
private final EventExecutor executor;
private final Queue<Runnable> tasks = PlatformDependent.newMpscQueue();
private static final int NONE = 0;
private static final int SUBMITTED = 1;
private static final int RUNNING = 2;
private final AtomicInteger state = new AtomicInteger();
private final int maxTaskExecutePerRun;
private final AtomicReference<Thread> executingThread = new AtomicReference<Thread>();
NonStickyOrderedEventExecutor(EventExecutor executor, int maxTaskExecutePerRun) {
super(executor);
this.executor = executor;
this.maxTaskExecutePerRun = maxTaskExecutePerRun;
}
@Override
public void run() {
if (!state.compareAndSet(SUBMITTED, RUNNING)) {
return;
}
Thread current = Thread.currentThread();
executingThread.set(current);
for (;;) {
int i = 0;
try {
for (; i < maxTaskExecutePerRun; i++) {
Runnable task = tasks.poll();
if (task == null) {
break;
}
safeExecute(task);
}
} finally {
if (i == maxTaskExecutePerRun) {
try {
state.set(SUBMITTED);
// Only set executingThread to null if no other thread did update it yet.
executingThread.compareAndSet(current, null);
executor.execute(this);
return; // done
} catch (Throwable ignore) {
// Reset the state back to running as we will keep on executing tasks.
state.set(RUNNING);
// if an error happened we should just ignore it and let the loop run again as there is not
// much else we can do. Most likely this was triggered by a full task queue. In this case
// we just will run more tasks and try again later.
}
} else {
state.set(NONE);
// After setting the state to NONE, look at the tasks queue one more time.
// If it is empty, then we can return from this method.
// Otherwise, it means the producer thread has called execute(Runnable)
// and enqueued a task in between the tasks.poll() above and the state.set(NONE) here.
// There are two possible scenarios when this happens
//
// 1. The producer thread sees state == NONE, hence the compareAndSet(NONE, SUBMITTED)
// is successfully setting the state to SUBMITTED. This mean the producer
// will call / has called executor.execute(this). In this case, we can just return.
// 2. The producer thread don't see the state change, hence the compareAndSet(NONE, SUBMITTED)
// returns false. In this case, the producer thread won't call executor.execute.
// In this case, we need to change the state to RUNNING and keeps running.
//
// The above cases can be distinguished by performing a
// compareAndSet(NONE, RUNNING). If it returns "false", it is case 1; otherwise it is case 2.
if (tasks.isEmpty() || !state.compareAndSet(NONE, RUNNING)) {
// Only set executingThread to null if no other thread did update it yet.
executingThread.compareAndSet(current, null);
return; // done
}
}
}
}
}
@Override
public boolean inEventLoop(Thread thread) {
return executingThread.get() == thread;
}
@Override
public boolean isShuttingDown() {
return executor.isShutdown();
}
@Override
public Future<?> shutdownGracefully(long quietPeriod, long timeout, TimeUnit unit) {
return executor.shutdownGracefully(quietPeriod, timeout, unit);
}
@Override
public Future<?> terminationFuture() {
return executor.terminationFuture();
}
@Override
public void shutdown() {
executor.shutdown();
}
@Override
public boolean isShutdown() {
return executor.isShutdown();
}
@Override
public boolean isTerminated() {
return executor.isTerminated();
}
@Override
public boolean awaitTermination(long timeout, TimeUnit unit) throws InterruptedException {
return executor.awaitTermination(timeout, unit);
}
@Override
public void execute(Runnable command) {
if (!tasks.offer(command)) {
throw new RejectedExecutionException();
}
if (state.compareAndSet(NONE, SUBMITTED)) {
// Actually it could happen that the runnable was picked up in between but we not care to much and just
// execute ourself. At worst this will be a NOOP when run() is called.
executor.execute(this);
}
}
}
}