/*

  * 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.utils;

 import org.apache.hadoop.mapreduce.Job;

 import java.io.IOException;

 /** Utility methods for dealing with counters */

 public class CounterUtils {

   /** Milliseconds to sleep for while waiting for counter to appear */

   private static final int SLEEP_MSECS = 100;

   /** Do not instantiate */

   private CounterUtils() {

   }

   /**

    * Wait for a counter to appear in a group and then return the name of that

    * counter. If job finishes before counter appears, return null.

    *

    * @param job   Job

    * @param group Name of the counter group

    * @return Name of the counter inside of the group, or null if job finishes

    *         before counter appears

    */

   public static String waitAndGetCounterNameFromGroup(Job job, String group) {

     try {

       while (job.getCounters().getGroup(group).size() == 0) {

         if (job.isComplete()) {

           return null;

         }

         Thread.sleep(SLEEP_MSECS);

       }

       return job.getCounters().getGroup(group).iterator().next().getName();

     } catch (IOException | InterruptedException e) {

       throw new IllegalStateException(

           "waitAndGetCounterNameFromGroup: Exception occurred", e);

     }

   }

 }