[jira] Commented: (HADOOP-5929) Cleanup JobHistory file naming to do with job recovery

["Devaraj Das (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HADOOP-5929?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12713850#action_12713850 ] 

Devaraj Das commented on HADOOP-5929:
-------------------------------------

Also, we should remove the <date> field from the job history filename format. Anyway the date is already there in the jobID and that is a part of the filename.

> Cleanup JobHistory file naming to do with job recovery
> ------------------------------------------------------
>
>                 Key: HADOOP-5929
>                 URL: https://issues.apache.org/jira/browse/HADOOP-5929
>             Project: Hadoop Core
>          Issue Type: Bug
>          Components: mapred
>    Affects Versions: 0.19.0
>            Reporter: Devaraj Das
>             Fix For: 0.21.0
>
>
> The JobTracker uses the job history files for doing job recovery upon startup. To handle cases where JobTracker goes down again while the recovered job is running, there is some logic that plays with files and it ends up having two history files for some window of time during the life of the job - actual history file, .recover file. The idea being that upon the next restart we should be able to the maximal number of events for the job. It led to performance problems in the job submission / recovery (part of which got addressed in HADOOP-4372). It also looks pretty unlikely that a running job will traverse across multiple JT restarts. Even if it did, without the .recover file, it'd only mean that we lose some tasks that got completed in a subsequent restart. I propose that we remove the .recover file logic and base the recovery on only the original job history file. 

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