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From "Jason Lowe (JIRA)" <j...@apache.org>
Subject [jira] [Created] (MAPREDUCE-5268) Improve history server startup performance
Date Wed, 22 May 2013 20:12:22 GMT
Jason Lowe created MAPREDUCE-5268:

             Summary: Improve history server startup performance
                 Key: MAPREDUCE-5268
                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-5268
             Project: Hadoop Map/Reduce
          Issue Type: Improvement
          Components: jobhistoryserver
    Affects Versions: 2.0.4-alpha, 0.23.7
            Reporter: Jason Lowe

The history server can easily take many minutes to startup when there are a significant number
of jobs to scan in the done directory.  However the scanning of files is not the bottleneck,
rather it's the heavy use of ConcurrentSkipListMap.size in HistoryFileManager.  

ConcurrentSkipListMap.size is a very expensive operation, especially on maps with many entries,
as it has to scan every entry to compute the size.  We should avoid calling this method or
at least minimize its use.

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