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From "Alan Gates (JIRA)" <j...@apache.org>
Subject [jira] Updated: (PIG-179) On hadoop 0.16, some jobs using combiner fail with an NPE
Date Wed, 02 Apr 2008 22:09:24 GMT

     [ https://issues.apache.org/jira/browse/PIG-179?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Alan Gates updated PIG-179:

    Status: Patch Available  (was: Open)

A patch that removes the ThreadLocal modifier for the PigRecordReader.  According to Ben Reed
(who wrote this) he originally made it thread local because he was concerned that hadoop might
change to run multiple maps in the same JVM.  As that does not now seem likely converting
this ThreadLocal to static will be safe and not cause and NPE in cases where the RecordReader,
Mapper, and Combiner aren't all running in the same thread.

> On hadoop 0.16, some jobs using combiner fail with an NPE
> ---------------------------------------------------------
>                 Key: PIG-179
>                 URL: https://issues.apache.org/jira/browse/PIG-179
>             Project: Pig
>          Issue Type: Bug
>    Affects Versions: 0.0.0
>         Environment: Hadoop 0.16
>            Reporter: Alan Gates
>            Assignee: Alan Gates
>         Attachments: PIG-179.patch
> Some jobs (it appears to only be larger jobs) now fail with an NPE in the combiner code
on this line:
> {code}
> PigSplit split = PigInputFormat.PigRecordReader.getPigRecordReader().getPigFileSplit();
> {code}
> Looking into the PigRecordReader a comment in the class indicates that, as implemented,
it depends on the mapper and splitter (and in this case the combiner as well) running in the
same thread.  It seems that in some cases in hadoop 0.16 this is no longer the case.

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