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  1. Hadoop Common
  2. HADOOP-4666

Launch reduces only after a few maps have run in the Fair Scheduler

    Details

    • Type: Improvement
    • Status: Closed
    • Priority: Major
    • Resolution: Fixed
    • Affects Version/s: None
    • Fix Version/s: 0.20.0
    • Component/s: None
    • Labels:
      None
    • Hadoop Flags:
      Reviewed

      Description

      It makes no sense to schedule reduces for a job before its maps have started running. As an initial fix, we will wait until a certain percent have run (likely 10%). In the future it would be good to choose the time to wait based on amount of map output data as well - launching reducers that will mostly be idle is not helpful. Average amount of map output bytes per mapper is easy to compute using counters in JobInProgress.

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            • Assignee:
              matei@eecs.berkeley.edu Matei Zaharia
              Reporter:
              matei Matei Zaharia
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              • Created:
                Updated:
                Resolved: