org.apache.hadoop.util.SemaphoredDelegatingExecutor Maven / Gradle / Ivy
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* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF 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
*
* 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 org.apache.hadoop.util;
import org.apache.hadoop.thirdparty.com.google.common.util.concurrent.ForwardingExecutorService;
import org.apache.hadoop.thirdparty.com.google.common.util.concurrent.Futures;
import org.apache.hadoop.classification.InterfaceAudience;
import java.util.Collection;
import java.util.List;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Future;
import java.util.concurrent.Semaphore;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
/**
* This ExecutorService blocks the submission of new tasks when its queue is
* already full by using a semaphore. Task submissions require permits, task
* completions release permits.
*
* This is a refactoring of {@link BlockingThreadPoolExecutorService}; that code
* contains the thread pool logic, whereas this isolates the semaphore
* and submit logic for use with other thread pools and delegation models.
*
* This is inspired by
* this s4 threadpool
*/
@SuppressWarnings("NullableProblems")
@InterfaceAudience.Private
public class SemaphoredDelegatingExecutor extends
ForwardingExecutorService {
private final Semaphore queueingPermits;
private final ExecutorService executorDelegatee;
private final int permitCount;
/**
* Instantiate.
* @param executorDelegatee Executor to delegate to
* @param permitCount number of permits into the queue permitted
* @param fair should the semaphore be "fair"
*/
public SemaphoredDelegatingExecutor(
ExecutorService executorDelegatee,
int permitCount,
boolean fair) {
this.permitCount = permitCount;
queueingPermits = new Semaphore(permitCount, fair);
this.executorDelegatee = executorDelegatee;
}
@Override
protected ExecutorService delegate() {
return executorDelegatee;
}
@Override
public List> invokeAll(Collection> tasks)
throws InterruptedException {
throw new RuntimeException("Not implemented");
}
@Override
public List> invokeAll(Collection> tasks,
long timeout, TimeUnit unit) throws InterruptedException {
throw new RuntimeException("Not implemented");
}
@Override
public T invokeAny(Collection> tasks)
throws InterruptedException, ExecutionException {
throw new RuntimeException("Not implemented");
}
@Override
public T invokeAny(Collection> tasks, long timeout,
TimeUnit unit)
throws InterruptedException, ExecutionException, TimeoutException {
throw new RuntimeException("Not implemented");
}
@Override
public Future submit(Callable task) {
try {
queueingPermits.acquire();
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
return Futures.immediateFailedFuture(e);
}
return super.submit(new CallableWithPermitRelease<>(task));
}
@Override
public Future submit(Runnable task, T result) {
try {
queueingPermits.acquire();
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
return Futures.immediateFailedFuture(e);
}
return super.submit(new RunnableWithPermitRelease(task), result);
}
@Override
public Future submit(Runnable task) {
try {
queueingPermits.acquire();
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
return Futures.immediateFailedFuture(e);
}
return super.submit(new RunnableWithPermitRelease(task));
}
@Override
public void execute(Runnable command) {
try {
queueingPermits.acquire();
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
}
super.execute(new RunnableWithPermitRelease(command));
}
/**
* Get the number of permits available; guaranteed to be
* {@code 0 <= availablePermits <= size}.
* @return the number of permits available at the time of invocation.
*/
public int getAvailablePermits() {
return queueingPermits.availablePermits();
}
/**
* Get the number of threads waiting to acquire a permit.
* @return snapshot of the length of the queue of blocked threads.
*/
public int getWaitingCount() {
return queueingPermits.getQueueLength();
}
/**
* Total number of permits.
* @return the number of permits as set in the constructor
*/
public int getPermitCount() {
return permitCount;
}
@Override
public String toString() {
final StringBuilder sb = new StringBuilder(
"SemaphoredDelegatingExecutor{");
sb.append("permitCount=").append(getPermitCount())
.append(", available=").append(getAvailablePermits())
.append(", waiting=").append(getWaitingCount())
.append('}');
return sb.toString();
}
/**
* Releases a permit after the task is executed.
*/
class RunnableWithPermitRelease implements Runnable {
private Runnable delegatee;
RunnableWithPermitRelease(Runnable delegatee) {
this.delegatee = delegatee;
}
@Override
public void run() {
try {
delegatee.run();
} finally {
queueingPermits.release();
}
}
}
/**
* Releases a permit after the task is completed.
*/
class CallableWithPermitRelease implements Callable {
private Callable delegatee;
CallableWithPermitRelease(Callable delegatee) {
this.delegatee = delegatee;
}
@Override
public T call() throws Exception {
try {
return delegatee.call();
} finally {
queueingPermits.release();
}
}
}
}