content: /**
   * 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.ambari.server.utils;
  
  import java.util.concurrent.BlockingQueue;
  import java.util.concurrent.Executors;
  import java.util.concurrent.ThreadPoolExecutor;
  import java.util.concurrent.TimeUnit;
  import java.util.concurrent.locks.Condition;
  import java.util.concurrent.locks.ReentrantLock;
  
  /**
   * ThreadPoolExecutor extension which is stopped by default and can be started & stopped.
   */
  public class ManagedThreadPoolExecutor extends ThreadPoolExecutor {
  
    private volatile boolean isStopped;
    private final ReentrantLock pauseLock = new ReentrantLock();
    private final Condition unpaused = pauseLock.newCondition();
  
    public ManagedThreadPoolExecutor(int corePoolSize, int maximumPoolSize,
                              long keepAliveTime, TimeUnit unit,
                              BlockingQueue<Runnable> workQueue) {
      super(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue,
              Executors.defaultThreadFactory());
      isStopped = true;
    }
  
    @Override
    protected void beforeExecute(Thread t, Runnable r) {
      super.beforeExecute(t, r);
      pauseLock.lock();
      try {
        while (isStopped) {
          unpaused.await();
        }
      } catch (InterruptedException ie) {
        t.interrupt();
      } finally {
        pauseLock.unlock();
      }
    }
  
    public void start() {
      pauseLock.lock();
      try {
        isStopped = false;
        unpaused.signalAll();
      } finally {
        pauseLock.unlock();
      }
    }
  
    public void stop() {
      pauseLock.lock();
      try {
        isStopped = true;
      } finally {
        pauseLock.unlock();
      }
    }
  
    public boolean isRunning() {
      return !isStopped;
    }
  
  }
  