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HystrixContextScheduler.java
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HystrixContextScheduler.java
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/**
* Copyright 2013 Netflix, Inc.
*
* 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.netflix.hystrix.strategy.concurrency;
import java.util.concurrent.*;
import rx.*;
import rx.functions.Action0;
import rx.functions.Func0;
import rx.internal.schedulers.ScheduledAction;
import rx.subscriptions.*;
import com.netflix.hystrix.HystrixThreadPool;
import com.netflix.hystrix.strategy.HystrixPlugins;
/**
* Wrap a {@link Scheduler} so that scheduled actions are wrapped with {@link HystrixContexSchedulerAction} so that
* the {@link HystrixRequestContext} is properly copied across threads (if they are used by the {@link Scheduler}).
*/
public class HystrixContextScheduler extends Scheduler {
private final HystrixConcurrencyStrategy concurrencyStrategy;
private final Scheduler actualScheduler;
private final HystrixThreadPool threadPool;
public HystrixContextScheduler(Scheduler scheduler) {
this.actualScheduler = scheduler;
this.concurrencyStrategy = HystrixPlugins.getInstance().getConcurrencyStrategy();
this.threadPool = null;
}
public HystrixContextScheduler(HystrixConcurrencyStrategy concurrencyStrategy, Scheduler scheduler) {
this.actualScheduler = scheduler;
this.concurrencyStrategy = concurrencyStrategy;
this.threadPool = null;
}
public HystrixContextScheduler(HystrixConcurrencyStrategy concurrencyStrategy, HystrixThreadPool threadPool) {
this(concurrencyStrategy, threadPool, new Func0<Boolean>() {
@Override
public Boolean call() {
return true;
}
});
}
public HystrixContextScheduler(HystrixConcurrencyStrategy concurrencyStrategy, HystrixThreadPool threadPool, Func0<Boolean> shouldInterruptThread) {
this.concurrencyStrategy = concurrencyStrategy;
this.threadPool = threadPool;
this.actualScheduler = new ThreadPoolScheduler(threadPool, shouldInterruptThread);
}
@Override
public Worker createWorker() {
return new HystrixContextSchedulerWorker(actualScheduler.createWorker());
}
private class HystrixContextSchedulerWorker extends Worker {
private final Worker worker;
private HystrixContextSchedulerWorker(Worker actualWorker) {
this.worker = actualWorker;
}
@Override
public void unsubscribe() {
worker.unsubscribe();
}
@Override
public boolean isUnsubscribed() {
return worker.isUnsubscribed();
}
@Override
public Subscription schedule(Action0 action, long delayTime, TimeUnit unit) {
if (threadPool != null) {
if (!threadPool.isQueueSpaceAvailable()) {
throw new RejectedExecutionException("Rejected command because thread-pool queueSize is at rejection threshold.");
}
}
return worker.schedule(new HystrixContexSchedulerAction(concurrencyStrategy, action), delayTime, unit);
}
@Override
public Subscription schedule(Action0 action) {
if (threadPool != null) {
if (!threadPool.isQueueSpaceAvailable()) {
throw new RejectedExecutionException("Rejected command because thread-pool queueSize is at rejection threshold.");
}
}
return worker.schedule(new HystrixContexSchedulerAction(concurrencyStrategy, action));
}
}
private static class ThreadPoolScheduler extends Scheduler {
private final HystrixThreadPool threadPool;
private final Func0<Boolean> shouldInterruptThread;
public ThreadPoolScheduler(HystrixThreadPool threadPool, Func0<Boolean> shouldInterruptThread) {
this.threadPool = threadPool;
this.shouldInterruptThread = shouldInterruptThread;
}
@Override
public Worker createWorker() {
return new ThreadPoolWorker(threadPool, shouldInterruptThread);
}
}
/**
* Purely for scheduling work on a thread-pool.
* <p>
* This is not natively supported by RxJava as of 0.18.0 because thread-pools
* are contrary to sequential execution.
* <p>
* For the Hystrix case, each Command invocation has a single action so the concurrency
* issue is not a problem.
*/
private static class ThreadPoolWorker extends Worker {
private final HystrixThreadPool threadPool;
private final CompositeSubscription subscription = new CompositeSubscription();
private final Func0<Boolean> shouldInterruptThread;
public ThreadPoolWorker(HystrixThreadPool threadPool, Func0<Boolean> shouldInterruptThread) {
this.threadPool = threadPool;
this.shouldInterruptThread = shouldInterruptThread;
}
@Override
public void unsubscribe() {
subscription.unsubscribe();
}
@Override
public boolean isUnsubscribed() {
return subscription.isUnsubscribed();
}
@Override
public Subscription schedule(final Action0 action) {
if (subscription.isUnsubscribed()) {
// don't schedule, we are unsubscribed
return Subscriptions.unsubscribed();
}
// This is internal RxJava API but it is too useful.
ScheduledAction sa = new ScheduledAction(action);
subscription.add(sa);
sa.addParent(subscription);
ThreadPoolExecutor executor = (ThreadPoolExecutor) threadPool.getExecutor();
FutureTask<?> f = (FutureTask<?>) executor.submit(sa);
sa.add(new FutureCompleterWithConfigurableInterrupt(f, shouldInterruptThread, executor));
return sa;
}
@Override
public Subscription schedule(Action0 action, long delayTime, TimeUnit unit) {
throw new IllegalStateException("Hystrix does not support delayed scheduling");
}
}
/**
* Very similar to rx.internal.schedulers.ScheduledAction.FutureCompleter, but with configurable interrupt behavior
*/
private static class FutureCompleterWithConfigurableInterrupt implements Subscription {
private final FutureTask<?> f;
private final Func0<Boolean> shouldInterruptThread;
private final ThreadPoolExecutor executor;
private FutureCompleterWithConfigurableInterrupt(FutureTask<?> f, Func0<Boolean> shouldInterruptThread, ThreadPoolExecutor executor) {
this.f = f;
this.shouldInterruptThread = shouldInterruptThread;
this.executor = executor;
}
@Override
public void unsubscribe() {
executor.remove(f);
if (shouldInterruptThread.call()) {
f.cancel(true);
} else {
f.cancel(false);
}
}
@Override
public boolean isUnsubscribed() {
return f.isCancelled();
}
}
}