/*

  * 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.graph;

 import org.apache.commons.lang3.exception.ExceptionUtils;

 import org.apache.giraph.writable.kryo.KryoWritableWrapper;

 import org.apache.hadoop.filecache.DistributedCache;

 import org.apache.hadoop.io.Writable;

 import org.apache.hadoop.io.WritableComparable;

 import org.apache.hadoop.mapreduce.Mapper;

 import org.apache.log4j.Logger;

 import java.io.IOException;

 /**

  * This mapper that will execute the BSP graph tasks alloted to this worker.

  * All tasks will be performed by calling the GraphTaskManager object managed by

  * this GraphMapper wrapper classs. Since this mapper will

  * not be passing data by key-value pairs through the MR framework, the

  * Mapper parameter types are irrelevant, and set to <code>Object</code> type.

  *

  * @param <I> Vertex id

  * @param <V> Vertex data

  * @param <E> Edge data

  */

 @SuppressWarnings("rawtypes")

 public class GraphMapper<I extends WritableComparable, V extends Writable,

     E extends Writable> extends

     Mapper<Object, Object, Object, Object> {

   /** Class logger */

   private static final Logger LOG = Logger.getLogger(GraphMapper.class);

   /** Manage the framework-agnostic Giraph tasks for this job run */

   private GraphTaskManager<I, V, E> graphTaskManager;

   @Override

   public void setup(Context context)

     throws IOException, InterruptedException {

     // Execute all Giraph-related role(s) assigned to this compute node.

     // Roles can include "master," "worker," "zookeeper," or . . . ?

     graphTaskManager = new GraphTaskManager<I, V, E>(context);

     graphTaskManager.setup(

       DistributedCache.getLocalCacheArchives(context.getConfiguration()));

   }

   /**

    * GraphMapper is designed to host the compute node in a Hadoop

    * Mapper task. The GraphTaskManager owned by GraphMapper manages all

    * framework-independent Giraph BSP operations for this job run.

    * @param key unused arg required by Mapper API

    * @param value unused arg required by Mapper API

    * @param context the Mapper#Context required to report progress

    *                to the underlying cluster

    */

   @Override

   public void map(Object key, Object value, Context context)

     throws IOException, InterruptedException {

     // a no-op in Giraph

   }

   @Override

   public void cleanup(Context context)

     throws IOException, InterruptedException {

     graphTaskManager.cleanup();

     graphTaskManager.sendWorkerCountersAndFinishCleanup();

   }

   @Override

   public void run(Context context) throws IOException, InterruptedException {

     // Notify the master quicker if there is worker failure rather than

     // waiting for ZooKeeper to timeout and delete the ephemeral znodes

     try {

       setup(context);

       while (context.nextKeyValue()) {

         graphTaskManager.execute();

       }

       cleanup(context);

       // Checkstyle exception due to needing to dump ZooKeeper failure

       // on exception

       // CHECKSTYLE: stop IllegalCatch

     } catch (RuntimeException e) {

       // CHECKSTYLE: resume IllegalCatch

       byte [] exByteArray = KryoWritableWrapper.convertToByteArray(e);

       LOG.error("Caught an unrecoverable exception " + e.getMessage(), e);

       graphTaskManager.getJobProgressTracker().logError(

           "Exception occurred on mapper " +

               graphTaskManager.getConf().getTaskPartition() + ": " +

               ExceptionUtils.getStackTrace(e), exByteArray);

       graphTaskManager.zooKeeperCleanup();

       graphTaskManager.workerFailureCleanup();

       throw new IllegalStateException(

           "run: Caught an unrecoverable exception " + e.getMessage(), e);

     }

   }

 }