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https://issues.apache.org/jira/browse/MAPREDUCE-6251?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14540287#comment-14540287
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Craig Welch commented on MAPREDUCE-6251:
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None of the checkstyle warnings appear to be significant.
> JobClient needs additional retries at a higher level to address
> not-immediately-consistent dfs corner cases
> -----------------------------------------------------------------------------------------------------------
>
> Key: MAPREDUCE-6251
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-6251
> Project: Hadoop Map/Reduce
> Issue Type: Bug
> Components: jobhistoryserver, mrv2
> Affects Versions: 2.6.0
> Reporter: Craig Welch
> Assignee: Craig Welch
> Labels: BB2015-05-TBR
> Attachments: MAPREDUCE-6251.0.patch, MAPREDUCE-6251.1.patch,
> MAPREDUCE-6251.2.patch, MAPREDUCE-6251.3.patch, MAPREDUCE-6251.4.patch,
> MAPREDUCE-6251.6.patch, MAPREDUCE-6251.7.patch, MAPREDUCE-6251.8.patch,
> MAPREDUCE-6251.8.patch
>
>
> The JobClient is used to get job status information for running and completed
> jobs. Final state and history for a job is communicated from the application
> master to the job history server via a distributed file system - where the
> history is uploaded by the application master to the dfs and then
> scanned/loaded by the jobhistory server. While HDFS has strong consistency
> guarantees not all Hadoop DFS's do. When used in conjunction with a
> distributed file system which does not have this guarantee there will be
> cases where the history server may not see an uploaded file, resulting in the
> dreaded "no such job" and a null value for the RunningJob in the client.
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