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https://issues.apache.org/jira/browse/MAPREDUCE-7177?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16758880#comment-16758880
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Zhaohui Xin commented on MAPREDUCE-7177:
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Hi, [~ajisakaa]. This is really a problem when writing data with TestDFSIO. So
I recommend turning off speculation execution at TestDFSIO. Can you help me
review this patch? :D
> Disable speculative execution in TestDFSIO
> ------------------------------------------
>
> Key: MAPREDUCE-7177
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-7177
> Project: Hadoop Map/Reduce
> Issue Type: Bug
> Affects Versions: 3.2.0, 2.8.5
> Reporter: Kihwal Lee
> Assignee: Zhaohui Xin
> Priority: Major
> Attachments: MAPREDUCE-7177.001.patch
>
>
> When TestDFSIO runs in a certain environment where a subset of mappers are
> slow, the speculative execution can start. In the write phase, this will
> make existing mapper to fail in next addBlock() since the output files are
> overwritten.
> To make the benchmark more predictable and repeatable, speculation must be
> implicitly disabled in TestDFSIO itself.
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