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  1. Hadoop Map/Reduce
  2. MAPREDUCE-4892

CombineFileInputFormat node input split can be skewed on small clusters

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    Details

    • Type: Bug
    • Status: Closed
    • Priority: Major
    • Resolution: Fixed
    • Affects Version/s: None
    • Fix Version/s: 2.1.0-beta
    • Component/s: None
    • Labels:
      None
    • Hadoop Flags:
      Reviewed

      Description

      The CombineFileInputFormat split generation logic tries to group blocks by node in order to create splits. It iterates through the nodes and creates splits on them until there aren't enough blocks left on a node that can be grouped into a valid split. If the first few nodes have a lot of blocks on them then they can end up getting a disproportionately large share of the total number of splits created. This can result in poor locality of maps. This problem is likely to happen on small clusters where its easier to create a skew in the distribution of blocks on nodes.

        Attachments

        1. MAPREDUCE-4892.1.alt.patch
          23 kB
          Vinod Kumar Vavilapalli
        2. MAPREDUCE-4892.1.alt.patch
          23 kB
          Bikas Saha
        3. MAPREDUCE-4892.1.patch
          20 kB
          Bikas Saha

          Activity

            People

            • Assignee:
              bikassaha Bikas Saha
              Reporter:
              bikassaha Bikas Saha
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              Dates

              • Created:
                Updated:
                Resolved: