/*

  * 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.bsp;

 import org.apache.giraph.conf.GiraphConstants;

 import org.apache.hadoop.conf.Configuration;

 import org.apache.hadoop.io.Text;

 import org.apache.hadoop.mapreduce.InputFormat;

 import org.apache.hadoop.mapreduce.InputSplit;

 import org.apache.hadoop.mapreduce.JobContext;

 import org.apache.hadoop.mapreduce.RecordReader;

 import org.apache.hadoop.mapreduce.TaskAttemptContext;

 import org.apache.log4j.Logger;

 import java.io.IOException;

 import java.util.ArrayList;

 import java.util.List;

 /**

  * This InputFormat supports the BSP model by ensuring that the user specifies

  * how many splits (number of mappers) should be started simultaneously.

  * The number of splits depends on whether the master and worker processes are

  * separate.  It is not meant to do any meaningful split of user-data.

  */

 public class BspInputFormat extends InputFormat<Text, Text> {

   /** Class Logger */

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

   /**

    * Get the correct number of mappers based on the configuration

    *

    * @param conf Configuration to determine the number of mappers

    * @return Maximum number of tasks

    */

   public static int getMaxTasks(Configuration conf) {

     int maxWorkers = conf.getInt(GiraphConstants.MAX_WORKERS, 0);

     boolean splitMasterWorker = GiraphConstants.SPLIT_MASTER_WORKER.get(conf);

     int maxTasks = maxWorkers;

     // if this is a YARN job, separate ZK should already be running

     boolean isYarnJob = GiraphConstants.IS_PURE_YARN_JOB.get(conf);

     if (splitMasterWorker && !isYarnJob) {

       maxTasks += 1;

     }

     if (LOG.isDebugEnabled()) {

       LOG.debug("getMaxTasks: Max workers = " + maxWorkers +

           ", split master/worker = " + splitMasterWorker +

           ", is YARN-only job = " + isYarnJob +

           ", total max tasks = " + maxTasks);

     }

     return maxTasks;

   }

   @Override

   public List<InputSplit> getSplits(JobContext context)

     throws IOException, InterruptedException {

     Configuration conf = context.getConfiguration();

     int maxTasks = getMaxTasks(conf);

     if (maxTasks <= 0) {

       throw new InterruptedException(

           "getSplits: Cannot have maxTasks <= 0 - " + maxTasks);

     }

     List<InputSplit> inputSplitList = new ArrayList<InputSplit>();

     for (int i = 0; i < maxTasks; ++i) {

       inputSplitList.add(new BspInputSplit());

     }

     return inputSplitList;

   }

   @Override

   public RecordReader<Text, Text>

   createRecordReader(InputSplit split, TaskAttemptContext context)

     throws IOException, InterruptedException {

     return new BspRecordReader();

   }

 }