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https://issues.apache.org/jira/browse/MAPREDUCE-497?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Allen Wittenauer resolved MAPREDUCE-497.
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Resolution: Incomplete
Closing this as stale.
> TaskTracker.addDiagnostics(String file, int num, String tag) could exit early
> if num==0
> ---------------------------------------------------------------------------------------
>
> Key: MAPREDUCE-497
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-497
> Project: Hadoop Map/Reduce
> Issue Type: Improvement
> Reporter: Steve Loughran
> Priority: Minor
>
> When a TaskTracker job finishes, taskFinished() is invoked.
> as part of its work it
> 1. loads in a conf option (that is not in hadoop-default, incidentally) ,
> mapred.debug.out.lines , default value -1;
> 2. calls addDiagnostics passing in that line count
> addDiagnostics either builds a string buffer of all the output, or creates a
> linear array of lines and runs adds them, shuffling them up if there are more
> lines than expected.
> This is all unneeded if the number of lines to print == 0; the entire reading
> in of the output file can be skipped. This may speed up termination slightly
> on a run with a large output file and mapred.debug.out.lines ==0.
> Note also that a circular buffer would handle the lines>0 problem without
> having to copy all the strings around.
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