com.google.cloud.dataflow.sdk.util.BoundedQueueExecutor Maven / Gradle / Ivy

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/*
 * Copyright (C) 2015 Google 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.google.cloud.dataflow.sdk.util;

import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.Semaphore;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;

/**
 * Executor that blocks on execute() if its queue is full.
 */
public class BoundedQueueExecutor extends ThreadPoolExecutor {
  private static class ReducableSemaphore extends Semaphore {
    private static final long serialVersionUID = 0;

    ReducableSemaphore(int permits) {
      super(permits);
    }

    @Override
    public void reducePermits(int permits) {
      super.reducePermits(permits);
    }
  }
  private ReducableSemaphore semaphore;

  public BoundedQueueExecutor(int maximumPoolSize,
                   long keepAliveTime,
                   TimeUnit unit,
                   int maximumQueueSize,
                   ThreadFactory threadFactory) {
    super(maximumPoolSize, maximumPoolSize, keepAliveTime, unit,
        new LinkedBlockingQueue(), threadFactory);
    this.semaphore = new ReducableSemaphore(maximumQueueSize);
    allowCoreThreadTimeOut(true);
  }

  // Before adding a Runnable to the queue, acquire the semaphore.
  @Override
  public void execute(Runnable r) {
    semaphore.acquireUninterruptibly();
    super.execute(r);
  }

  // Forcibly add something to the queue, ignoring the length limit.
  public void forceExecute(Runnable r) {
    semaphore.reducePermits(1);
    super.execute(r);
  }

  // Release the semaphore after taking a Runnable off the queue.
  @Override
  public void beforeExecute(Thread t, Runnable r) {
    semaphore.release();
  }
}