/*

  * 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.giraph.conf.IntConfOption;

 import org.apache.hadoop.conf.Configuration;

 import com.sun.management.GcInfo;

 /**

  * Tracks last k GC pauses and is able to tell how much time was spent doing

  * GC since some point in time. Thread safe.

  */

 public class GcTracker {

   /** How many last gcs to keep */

   public static final IntConfOption LAST_GCS_TO_KEEP =

       new IntConfOption("giraph.lastGcsToKeep", 100,

           "How many last gcs to keep");

   /** Last k GCs which happened */

   private final GcInfo[] lastKGcs;

   /** Next position to write gc to */

   private int positionInGcs = 0;

   /**

    * Constructor with default number of last gcs to keep

    */

   public GcTracker() {

     lastKGcs = new GcInfo[LAST_GCS_TO_KEEP.getDefaultValue()];

   }

   /**

    * Constructor with configuration

    *

    * @param conf Configuration

    */

   public GcTracker(Configuration conf) {

     lastKGcs = new GcInfo[LAST_GCS_TO_KEEP.get(conf)];

   }

   /**

    * Called to notify gc tracker that gc occurred

    *

    * @param gcInfo GC info

    */

   public synchronized void gcOccurred(GcInfo gcInfo) {

     lastKGcs[positionInGcs] = gcInfo;

     positionInGcs++;

     if (positionInGcs == lastKGcs.length) {

       positionInGcs = 0;

     }

   }

   /**

    * Check how much time was spent doing gc since some timestamp

    *

    * @param timeSinceJvmStarted Timestamp to measure from, you can use

    *     ManagementFactory.getRuntimeMXBean().getUptime() to get it

    * @return How much time was spent doing gc since that timestamp (if there

    * were more gcs than we are keeping (LAST_GCS_TO_KEEP) then it will be

    * partial result)

    */

   public synchronized long gcTimeSpentSince(long timeSinceJvmStarted) {

     long ret = 0;

     int currentPosition = positionInGcs;

     do {

       currentPosition--;

       if (currentPosition < 0) {

         currentPosition = lastKGcs.length - 1;

       }

       // If there was no such GC or GC started before the timestamp given,

       // stop iterating

       if (lastKGcs[currentPosition] == null ||

           lastKGcs[currentPosition].getStartTime() < timeSinceJvmStarted) {

         break;

       }

       ret += lastKGcs[currentPosition].getDuration();

     } while (currentPosition != positionInGcs);

     return ret;

   }

 }