samoa-threads/src/main/java/org/apache/samoa/topology/impl/ThreadsEngine.java

package org.apache.samoa.topology.impl;

/*
 * #%L
 * SAMOA
 * %%
 * Copyright (C) 2013 Yahoo! 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.
 * #L%
 */

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

import org.apache.samoa.topology.Topology;

/**
 * Multithreaded engine.
 * 
 * @author Anh Thu Vu
 * 
 */
public class ThreadsEngine {

  private static final List<ExecutorService> threadPool = new ArrayList<ExecutorService>();

  /*
   * Create and manage threads
   */
  public static void setNumberOfThreads(int numThreads) {
    if (numThreads < 1)
      throw new IllegalStateException("Number of threads must be a positive integer.");

    if (threadPool.size() > numThreads)
      throw new IllegalStateException("You cannot set a numThreads smaller than the current size of the threads pool.");

    if (threadPool.size() < numThreads) {
      for (int i = threadPool.size(); i < numThreads; i++) {
        threadPool.add(Executors.newSingleThreadExecutor());
      }
    }
  }

  public static int getNumberOfThreads() {
    return threadPool.size();
  }

  public static ExecutorService getThreadWithIndex(int index) {
    if (threadPool.size() <= 0)
      throw new IllegalStateException("Try to get ExecutorService from an empty pool.");
    index %= threadPool.size();
    return threadPool.get(index);
  }

  /*
   * Submit topology and start
   */
  private static void submitTopology(Topology topology) {
    ThreadsTopology tTopology = (ThreadsTopology) topology;
    tTopology.run();
  }

  public static void submitTopology(Topology topology, int numThreads) {
    ThreadsEngine.setNumberOfThreads(numThreads);
    ThreadsEngine.submitTopology(topology);
  }

  /*
   * Stop
   */
  public static void clearThreadPool() {
    for (ExecutorService pool : threadPool) {
      pool.shutdown();
    }

    for (ExecutorService pool : threadPool) {
      try {
        pool.awaitTermination(10, TimeUnit.SECONDS);
      } catch (InterruptedException e) {
        e.printStackTrace();
      }
    }

    threadPool.clear();
  }

}