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From "ZhuGuanyin (JIRA)" <j...@apache.org>
Subject [jira] Commented: (MAPREDUCE-1254) job.xml should add crc check in tasktracker and sub jvm.
Date Thu, 10 Dec 2009 10:38:21 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-1254?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12788657#action_12788657

ZhuGuanyin commented on MAPREDUCE-1254:

I just show the example that the inexpensive disk are not reliable, the kernel doesn't notice
the hardware failture while it has being truncated.

1)job.xml in configuration are loaded asynchronous, and if it could  corrupted or missing
before parse it, if it does happen, the corrupted data or default data would load without
notice(that means some task run the right configuration, but some would run with wrong configurations);

2)the job.xml has so many important parameters, it need check before used;

3) if it doesn't crc check, why we generate the crc checksum file?  :)

> job.xml should add crc check in tasktracker and sub jvm.
> --------------------------------------------------------
>                 Key: MAPREDUCE-1254
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-1254
>             Project: Hadoop Map/Reduce
>          Issue Type: New Feature
>          Components: task, tasktracker
>    Affects Versions: 0.22.0
>            Reporter: ZhuGuanyin
> Currently job.xml in tasktracker and subjvm are write to local disk through ChecksumFilesystem,
and already had crc checksum information, but load the job.xml file without crc check. It
would cause the mapred job finished successful but with wrong data because of disk error.
 Example: The tasktracker and sub task jvm would load the default configuration if it doesn't
successfully load the job.xml which maybe replace the mapper with IdentityMapper. 

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