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Revert f691cee and add BoundedScheduledThreadPoolExecutor back.
My personal experience with Reactor BoundedElasticScheduler has been nothing but suffering[1]. I am not happy with packaging something that should have been provided by Reactor, but this single file is still way simpler, maintainable, *and* without any catches compared to the BoundedElasticScheduler. [1] reactor/reactor-core#1992
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237 changes: 237 additions & 0 deletions
237
src/main/java/com/vlkan/pubsub/util/BoundedScheduledThreadPoolExecutor.java
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,237 @@ | ||
| /* | ||
| * Copyright 2019 Volkan Yazıcı | ||
| * | ||
| * 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 permits and | ||
| * limitations under the License. | ||
| */ | ||
|
|
||
| package com.vlkan.pubsub.util; | ||
|
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| import java.util.Collection; | ||
| import java.util.List; | ||
| import java.util.concurrent.*; | ||
|
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| /** | ||
| * A {@link ScheduledThreadPoolExecutor} wrapper enforcing a bound on the task | ||
| * queue size. Excessive task queue growth yields {@link | ||
| * RejectedExecutionException} errors. {@link RejectedExecutionHandler}s are | ||
| * not supported since they expect a {@link ThreadPoolExecutor} in their | ||
| * arguments. | ||
| * | ||
| * <p>Java Standard library unfortunately doesn't provide any {@link | ||
| * ScheduledExecutorService} implementations that one can provide a bound on | ||
| * the task queue. This shortcoming is prone to hide backpressure problems. See | ||
| * <a href="http://cs.oswego.edu/pipermail/concurrency-interest/2019-April/016861.html">the | ||
| * relevant concurrency-interest discussion</a> for {@link java.util.concurrent} | ||
| * lead Doug Lea's tip for enforcing a bound via {@link | ||
| * ScheduledThreadPoolExecutor#getQueue()}. | ||
| */ | ||
| @SuppressWarnings("NullableProblems") | ||
| public class BoundedScheduledThreadPoolExecutor implements ScheduledExecutorService { | ||
|
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| private final int queueCapacity; | ||
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| private final ScheduledThreadPoolExecutor executor; | ||
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| public BoundedScheduledThreadPoolExecutor( | ||
| int queueCapacity, | ||
| ScheduledThreadPoolExecutor executor) { | ||
| if (queueCapacity < 1) { | ||
| throw new IllegalArgumentException( | ||
| "was expecting a non-zero positive queue capacity"); | ||
| } | ||
| this.queueCapacity = queueCapacity; | ||
| this.executor = executor; | ||
| } | ||
|
|
||
| /** | ||
| * {@inheritDoc} | ||
| */ | ||
| @Override | ||
| public synchronized ScheduledFuture<?> schedule( | ||
| Runnable command, | ||
| long delay, | ||
| TimeUnit unit) { | ||
| ensureQueueCapacity(1); | ||
| return executor.schedule(command, delay, unit); | ||
| } | ||
|
|
||
| /** | ||
| * {@inheritDoc} | ||
| */ | ||
| @Override | ||
| public synchronized <V> ScheduledFuture<V> schedule( | ||
| Callable<V> callable, | ||
| long delay, | ||
| TimeUnit unit) { | ||
| ensureQueueCapacity(1); | ||
| return executor.schedule(callable, delay, unit); | ||
| } | ||
|
|
||
| /** | ||
| * {@inheritDoc} | ||
| */ | ||
| @Override | ||
| public synchronized ScheduledFuture<?> scheduleAtFixedRate( | ||
| Runnable command, | ||
| long initialDelay, | ||
| long period, | ||
| TimeUnit unit) { | ||
| ensureQueueCapacity(1); | ||
| return executor.scheduleAtFixedRate(command, initialDelay, period, unit); | ||
| } | ||
|
|
||
| /** | ||
| * {@inheritDoc} | ||
| */ | ||
| @Override | ||
| public ScheduledFuture<?> scheduleWithFixedDelay( | ||
| Runnable command, | ||
| long initialDelay, | ||
| long delay, | ||
| TimeUnit unit) { | ||
| ensureQueueCapacity(1); | ||
| return executor.scheduleWithFixedDelay(command, initialDelay, delay, unit); | ||
| } | ||
|
|
||
| /** | ||
| * {@inheritDoc} | ||
| */ | ||
| @Override | ||
| public void shutdown() { | ||
| executor.shutdown(); | ||
| } | ||
|
|
||
| /** | ||
| * {@inheritDoc} | ||
| */ | ||
| @Override | ||
| public List<Runnable> shutdownNow() { | ||
| return executor.shutdownNow(); | ||
| } | ||
|
|
||
| /** | ||
| * {@inheritDoc} | ||
| */ | ||
| @Override | ||
| public boolean isShutdown() { | ||
| return executor.isShutdown(); | ||
| } | ||
|
|
||
| /** | ||
| * {@inheritDoc} | ||
| */ | ||
| @Override | ||
| public boolean isTerminated() { | ||
| return executor.isTerminated(); | ||
| } | ||
|
|
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| /** | ||
| * {@inheritDoc} | ||
| */ | ||
| @Override | ||
| public boolean awaitTermination(long timeout, TimeUnit unit) | ||
| throws InterruptedException { | ||
| return executor.awaitTermination(timeout, unit); | ||
| } | ||
|
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| /** | ||
| * {@inheritDoc} | ||
| */ | ||
| @Override | ||
| public synchronized <T> Future<T> submit(Callable<T> task) { | ||
| ensureQueueCapacity(1); | ||
| return executor.submit(task); | ||
| } | ||
|
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| /** | ||
| * {@inheritDoc} | ||
| */ | ||
| @Override | ||
| public synchronized <T> Future<T> submit(Runnable task, T result) { | ||
| ensureQueueCapacity(1); | ||
| return executor.submit(task, result); | ||
| } | ||
|
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| /** | ||
| * {@inheritDoc} | ||
| */ | ||
| @Override | ||
| public synchronized Future<?> submit(Runnable task) { | ||
| ensureQueueCapacity(1); | ||
| return executor.submit(task); | ||
| } | ||
|
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||
| /** | ||
| * {@inheritDoc} | ||
| */ | ||
| @Override | ||
| public synchronized <T> List<Future<T>> invokeAll( | ||
| Collection<? extends Callable<T>> tasks) | ||
| throws InterruptedException { | ||
| ensureQueueCapacity(tasks.size()); | ||
| return executor.invokeAll(tasks); | ||
| } | ||
|
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| /** | ||
| * {@inheritDoc} | ||
| */ | ||
| @Override | ||
| public synchronized <T> List<Future<T>> invokeAll( | ||
| Collection<? extends Callable<T>> tasks, | ||
| long timeout, | ||
| TimeUnit unit) | ||
| throws InterruptedException { | ||
| ensureQueueCapacity(tasks.size()); | ||
| return executor.invokeAll(tasks, timeout, unit); | ||
| } | ||
|
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| /** | ||
| * {@inheritDoc} | ||
| */ | ||
| @Override | ||
| public synchronized <T> T invokeAny(Collection<? extends Callable<T>> tasks) | ||
| throws InterruptedException, ExecutionException { | ||
| ensureQueueCapacity(tasks.size()); | ||
| return executor.invokeAny(tasks); | ||
| } | ||
|
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| /** | ||
| * {@inheritDoc} | ||
| */ | ||
| @Override | ||
| public synchronized <T> T invokeAny( | ||
| Collection<? extends Callable<T>> tasks, | ||
| long timeout, | ||
| TimeUnit unit) | ||
| throws InterruptedException, ExecutionException, TimeoutException { | ||
| ensureQueueCapacity(tasks.size()); | ||
| return executor.invokeAny(tasks, timeout, unit); | ||
| } | ||
|
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| /** | ||
| * {@inheritDoc} | ||
| */ | ||
| @Override | ||
| public synchronized void execute(Runnable command) { | ||
| ensureQueueCapacity(1); | ||
| executor.submit(command); | ||
| } | ||
|
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| private void ensureQueueCapacity(int taskCount) { | ||
| int queueSize = executor.getQueue().size(); | ||
| if ((queueSize + taskCount) >= queueCapacity) { | ||
| throw new RejectedExecutionException(); | ||
| } | ||
| } | ||
|
|
||
| } |