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  1. Hadoop Map/Reduce
  2. MAPREDUCE-6919

ShuffleMetrics.ShuffleConnections Gauge Metric Rises Infinitely

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    Details

    • Type: Bug
    • Status: Open
    • Priority: Major
    • Resolution: Unresolved
    • Affects Version/s: None
    • Fix Version/s: None
    • Component/s: mrv2
    • Labels:
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      Description

      We recently noticed that the mapred.ShuffleMetrics.ShuffleConnections metric rises indefinitely (see attached graph), despite supposedly being a gauge measuring the number of currently open connections:

      ShuffleHandler.java
          @Metric("# of current shuffle connections")
              MutableGaugeInt shuffleConnections;
      

      It seems this is because the metric is incremented once for each map file sent, but decremented once for each request. Thus a request which fetches multiple map files permanently increments shuffleConnections by (mapsFetched - 1).

        Attachments

        1. mapred_ShuffleMetrics_ShuffleConnections.png
          10 kB
          Erik Krogen
        2. MAPREDUCE-6919.test.patch
          8 kB
          Erik Krogen

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              • Assignee:
                Unassigned
                Reporter:
                xkrogen Erik Krogen
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                • Created:
                  Updated: