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From "Robert Joseph Evans (JIRA)" <j...@apache.org>
Subject [jira] [Resolved] (MAPREDUCE-4303) Look at using String.intern to dedupe some Strings
Date Wed, 24 Oct 2012 14:04:13 GMT

     [ https://issues.apache.org/jira/browse/MAPREDUCE-4303?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Robert Joseph Evans resolved MAPREDUCE-4303.
--------------------------------------------

    Resolution: Duplicate
    
> 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: 0.23.3, 2.0.0-alpha
>            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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