001/**
002 *
003 * Licensed to the Apache Software Foundation (ASF) under one
004 * or more contributor license agreements.  See the NOTICE file
005 * distributed with this work for additional information
006 * regarding copyright ownership.  The ASF licenses this file
007 * to you under the Apache License, Version 2.0 (the
008 * "License"); you may not use this file except in compliance
009 * with the License.  You may obtain a copy of the License at
010 *
011 *     http://www.apache.org/licenses/LICENSE-2.0
012 *
013 * Unless required by applicable law or agreed to in writing, software
014 * distributed under the License is distributed on an "AS IS" BASIS,
015 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
016 * See the License for the specific language governing permissions and
017 * limitations under the License.
018 */
019
020package org.apache.hadoop.hbase.util;
021
022
023import java.util.ArrayList;
024import java.util.List;
025import java.util.concurrent.ArrayBlockingQueue;
026import java.util.concurrent.BlockingQueue;
027import java.util.concurrent.Callable;
028import java.util.concurrent.Executor;
029import java.util.concurrent.Future;
030import java.util.concurrent.FutureTask;
031import java.util.concurrent.TimeUnit;
032
033import org.apache.yetus.audience.InterfaceAudience;
034
035/**
036 * A completion service, close to the one available in the JDK 1.7
037 * However, this ones keeps the list of the future, and allows to cancel them all.
038 * This means as well that it can be used for a small set of tasks only.
039 * <br>Implementation is not Thread safe.
040 */
041@InterfaceAudience.Private
042public class BoundedCompletionService<V> {
043  private final Executor executor;
044  private final List<Future<V>> tasks; // alls the tasks
045  private final BlockingQueue<Future<V>> completed; // all the tasks that are completed
046
047  class QueueingFuture extends FutureTask<V> {
048
049    public QueueingFuture(Callable<V> callable) {
050      super(callable);
051    }
052
053    @Override
054    protected void done() {
055      completed.add(QueueingFuture.this);
056    }
057  }
058
059  public BoundedCompletionService(Executor executor, int maxTasks) {
060    this.executor = executor;
061    this.tasks = new ArrayList<>(maxTasks);
062    this.completed = new ArrayBlockingQueue<>(maxTasks);
063  }
064
065
066  public Future<V> submit(Callable<V> task) {
067    QueueingFuture newFuture = new QueueingFuture(task);
068    executor.execute(newFuture);
069    tasks.add(newFuture);
070    return newFuture;
071  }
072
073  public  Future<V> take() throws InterruptedException{
074    return completed.take();
075  }
076
077  public Future<V> poll(long timeout, TimeUnit unit) throws InterruptedException{
078    return completed.poll(timeout, unit);
079  }
080
081  public void cancelAll(boolean interrupt) {
082    for (Future<V> future : tasks) {
083      future.cancel(interrupt);
084    }
085  }
086}