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From "Robert Joseph Evans (JIRA)" <j...@apache.org>
Subject [jira] [Created] (MAPREDUCE-4303) Look at using String.intern to dedupe some Strings
Date Fri, 01 Jun 2012 19:20:22 GMT
Robert Joseph Evans created MAPREDUCE-4303:
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             Summary: Look at using String.intern to dedupe some Strings
                 Key: MAPREDUCE-4303
                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-4303
             Project: Hadoop Map/Reduce
          Issue Type: Improvement
          Components: applicationmaster
    Affects Versions: 2.0.0-alpha, 0.23.3
            Reporter: Robert Joseph Evans


MAPREDUCE-4301 fixes one issue with too many duplicate strings, but there are other places
where it is not as simple to remove the duplicates.  In these cases the source of the strings
is an incoming RPC call or from parsing and reading in a file.  The only real way to dedupe
these is to either use String.intern() which if not used properly could result in the permgen
space being filled up, or by playing games with our own cache, and trying to do the same sort
of thing as String.intern, but in the heap.

The following are some that I saw lots of duplicate strings that we should look at doing something
about.

TaskAttemptStatusUpdateEvent$TaskAttemptState.stateString
MapTaskAttemptImpl.diagnostics
The keys to Counters.groups
GenericGroup.displayName
The keys to GenericGroup.counters
and GenericCounter.displayName

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