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Date: Mon, 6 Jun 2011 21:06:59 +0000 (UTC)
From: "Todd Lipcon (JIRA)" <jira@apache.org>
To: mapreduce-issues@hadoop.apache.org
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Subject: [jira] [Commented] (MAPREDUCE-2557) Counters don't reset state when
 readFields() called
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    [ https://issues.apache.org/jira/browse/MAPREDUCE-2557?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13045107#comment-13045107 ] 

Todd Lipcon commented on MAPREDUCE-2557:
----------------------------------------

Hi William. Thanks for the bug report. Two things:
- a silly nit: can you use "1L" and "2L" instead of "1l" and "2l" in the tests? I was staring at it for 5 minutes before I realized those were 'l' ("ell") and not '1' ("one").
- what ramifications, if any, does this have on the MR framework itself? Would this cause incorrect counters in any usual use case? How'd you come across the bug?

> Counters don't reset state when readFields() called
> ---------------------------------------------------
>
>                 Key: MAPREDUCE-2557
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-2557
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>            Reporter: William Slacum
>            Priority: Trivial
>         Attachments: MAPREDUCE-2557.patch
>
>   Original Estimate: 0.5h
>  Remaining Estimate: 0.5h
>
> When calling readFields() on a Counters object, the internal state is not completely reset. The IdentityHashMap<Enum<?>, Counter> cache retains all previous mappings, even after the actual CounterGroups are changed. Using the same Counters pointer over and over again results in the cache always keeping the mapping for the first call to getCounter(Enum<?>). I've add a clear() call to the cache when readFields() is called and added a unit test to verify that it works.

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