/*
    * 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.giraph.ooc;
  
  import org.apache.giraph.utils.CallableFactory;
  import org.apache.giraph.utils.ThreadUtils;
  import org.apache.log4j.Logger;
  
  import java.util.ArrayList;
  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.LinkedBlockingQueue;
  import java.util.concurrent.ThreadPoolExecutor;
  import java.util.concurrent.TimeUnit;
  
  /**
   * Factory class to create IO threads for out-of-core engine.
   */
  public class OutOfCoreIOCallableFactory {
    /** Class logger. */
    private static final Logger LOG =
        Logger.getLogger(OutOfCoreIOCallableFactory.class);
    /** Out-of-core engine */
    private final OutOfCoreEngine oocEngine;
    /** Result of IO threads at the end of the computation */
    private final List<Future> results;
    /** Number of threads used for IO operations */
    private final int numIOThreads;
    /** Thread UncaughtExceptionHandler to use */
    private final Thread.UncaughtExceptionHandler uncaughtExceptionHandler;
    /** Executor service for IO threads */
    private ExecutorService outOfCoreIOExecutor;
  
    /**
     * Constructor
     * @param oocEngine Out-of-core engine
     * @param numIOThreads Number of IO threads used
     * @param uncaughtExceptionHandler Thread UncaughtExceptionHandler to use
     */
    public OutOfCoreIOCallableFactory(OutOfCoreEngine oocEngine,
        int numIOThreads,
        Thread.UncaughtExceptionHandler uncaughtExceptionHandler) {
      this.oocEngine = oocEngine;
      this.numIOThreads = numIOThreads;
      this.results = new ArrayList<>(numIOThreads);
      this.uncaughtExceptionHandler = uncaughtExceptionHandler;
    }
  
    /**
     * Creates/Launches IO threads
     */
    public void createCallable() {
      CallableFactory<Void> outOfCoreIOCallableFactory =
        new CallableFactory<Void>() {
          @Override
          public Callable<Void> newCallable(int callableId) {
            return new OutOfCoreIOCallable(oocEngine, callableId);
          }
        };
      outOfCoreIOExecutor = new ThreadPoolExecutor(numIOThreads, numIOThreads, 0L,
          TimeUnit.MILLISECONDS, new LinkedBlockingQueue<Runnable>(),
          ThreadUtils.createThreadFactory("ooc-io-%d"));
  
      for (int i = 0; i < numIOThreads; ++i) {
        Future<Void> future = ThreadUtils.submitToExecutor(outOfCoreIOExecutor,
            outOfCoreIOCallableFactory.newCallable(i), uncaughtExceptionHandler);
        results.add(future);
      }
      // Notify executor to not accept any more tasks
      outOfCoreIOExecutor.shutdown();
    }
  
    /**
     * Check whether all IO threads terminated gracefully.
     */
    public void shutdown() {
      boolean threadsTerminated = false;
      while (!threadsTerminated) {
        if (LOG.isInfoEnabled()) {
          LOG.info("shutdown: waiting for IO threads to finish!");
       }
       try {
         threadsTerminated =
             outOfCoreIOExecutor.awaitTermination(1000, TimeUnit.MILLISECONDS);
       } catch (InterruptedException e) {
         throw new IllegalStateException("shutdown: caught " +
             "InterruptedException while waiting for IO threads to finish");
       }
     }
     for (int i = 0; i < numIOThreads; ++i) {
       try {
         // Check whether the tread terminated gracefully
         results.get(i).get();
       } catch (InterruptedException e) {
         LOG.error("shutdown: IO thread " + i + " was interrupted during its " +
             "execution");
         throw new IllegalStateException(e);
       } catch (ExecutionException e) {
         LOG.error("shutdown: IO thread " + i + " threw an exception during " +
             "its execution");
         throw new IllegalStateException(e);
       }
     }
   }
 }