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  1. Hadoop Map/Reduce
  2. MAPREDUCE-6197

Cache MapOutputLocations in ShuffleHandler

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    Details

    • Type: Bug
    • Status: Resolved
    • Priority: Major
    • Resolution: Fixed
    • Affects Version/s: 2.6.0
    • Fix Version/s: 2.9.0, 3.0.0-alpha1
    • Component/s: None
    • Labels:
      None
    • Target Version/s:
    • Hadoop Flags:
      Reviewed

      Description

      ShuffleHandler currently seems to create a map of mapId - mapInfo (file.out / index information) when it receives a message.
      This should be caching map info across requests, so that the a scan of all directories is not required for each reducer fetching from the same map.

      Also, the scan for each map output / index file is performed twice per mapId within a request. In populateHeaders - once in the call to getMapOutputInfo, and then directly in the method.

      For an invocation where we do end up with more than 1000 (default) mapIds in a single call, and don't cache them in the map - the path constructed for such entries will be invalid. This is highly unlikely to be the case though, until there's proper caching.

      MapOutputInfo info = mapOutputInfoMap.get(mapId);
                if (info == null) {
                  info = getMapOutputInfo(outputBasePathStr, mapId, reduceId, user);
                }
      

        Attachments

        1. MAPREDUCE-6197.patch
          15 kB
          Junping Du

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              • Assignee:
                junping_du Junping Du
                Reporter:
                sseth Siddharth Seth
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                • Created:
                  Updated:
                  Resolved: