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From "Arun C Murthy (JIRA)" <j...@apache.org>
Subject [jira] Created: (HADOOP-3849) MapEventsFetcherThread doesn't wait for the heartbeat-interval if it doesn't have events to fetch
Date Tue, 29 Jul 2008 05:00:32 GMT
MapEventsFetcherThread doesn't wait for the heartbeat-interval if it doesn't have events to
fetch
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                 Key: HADOOP-3849
                 URL: https://issues.apache.org/jira/browse/HADOOP-3849
             Project: Hadoop Core
          Issue Type: Bug
          Components: mapred
    Affects Versions: 0.18.0
            Reporter: Arun C Murthy
            Assignee: Arun C Murthy
             Fix For: 0.19.0


The 'notify' done by FetchStatus.getMapEvents causes the MapEventsFetcherThread to immediately
run to the JobTracker (getTaskCompletionEvents). 

On a 3500 node cluster, I saw that each TaskTracker calls JobTracker.getTaskCompletionEvents
multiple times per-second. This caused the JobTracker's RPC queues to back-up resulting in
each RPC spending more than 120s in the queue - leading to shuffle proceeding very very slowly.

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