[
https://issues.apache.org/jira/browse/MAPREDUCE-5211?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Jason Lowe updated MAPREDUCE-5211:
----------------------------------
Attachment: MAPREDUCE-5211.branch-0.23.patch
Patch for branch-0.23 that adds the reduce task attempt ID to the output path
along with an increasing sequence number to keep the output files from
colliding.
No unit test, but manually tested to verify output paths for on disk merges are
emitted properly.
> Reducer intermediate files can collide during merge
> ---------------------------------------------------
>
> Key: MAPREDUCE-5211
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-5211
> Project: Hadoop Map/Reduce
> Issue Type: Bug
> Components: mrv2
> Affects Versions: 0.23.7
> Reporter: Jason Lowe
> Assignee: Jason Lowe
> Priority: Critical
> Attachments: MAPREDUCE-5211.branch-0.23.patch
>
>
> The OnDiskMerger.merge method constructs an output path that is not unique to
> a reduce attempt, and as a result can result in a file collision with other
> reducers from the same app that are running on the same node. In addition
> the name of the output file is based on MapOutput.toString which may not be
> unique in light of multi-pass merges on disk since the mapId will be null and
> the basename ends up as "MapOutput(null, DISK)"
--
This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators
For more information on JIRA, see: http://www.atlassian.com/software/jira
