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https://issues.apache.org/jira/browse/HADOOP-1876?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Arun C Murthy updated HADOOP-1876:
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Assignee: Alejandro Abdelnur
Status: Open (was: Patch Available)
bq. It seems to me that it would be much easier to retrofit the JobHistory to
use info out the files the patch is writing that the other way around.
I guess we should consider the fact that we might be better off, in the long
run, moving away from the custom, textual format used today by the
{{JobHistory}} and go the {{Writable}} way - much lesser and more standard
code. I don't believe the textual format buys us much, and is a pain to
maintain.
If folks agree, I'm okay with this patch going in as-is (oh, and yes, this is a
very different use-case) and then fixing {{JobHistory}} to use {{Writable}} to
serialize the necessary data-structures. Thoughts?
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That said, some comments about the patch:
Alejandro, could you please ensure that the {{completedJobsStoreThread}} isn't
_started at all_ if the feature is switched off?
Maybe we could add a boolean {{mapred.job.tracker.persist.jobstatus}} flag to
turn the feature on/off.
> Persisting completed jobs status
> --------------------------------
>
> Key: HADOOP-1876
> URL: https://issues.apache.org/jira/browse/HADOOP-1876
> Project: Hadoop
> Issue Type: Improvement
> Components: mapred
> Environment: all
> Reporter: Alejandro Abdelnur
> Assignee: Alejandro Abdelnur
> Priority: Critical
> Fix For: 0.16.0
>
> Attachments: patch1876.txt, patch1876.txt
>
>
> Currently the JobTracker keeps information about completed jobs in memory.
> This information is flushed from the cache when it has outlived
> (#RETIRE_JOB_INTERVAL) or because the limit of completed jobs in memory has
> been reach (#MAX_COMPLETE_USER_JOBS_IN_MEMORY).
> Also, if the JobTracker is restarted (due to being recycled or due to a
> crash) information about completed jobs is lost.
> If any of the above scenarios happens before the job information is queried
> by a hadoop client (normally the job submitter or a monitoring component)
> there is no way to obtain such information.
> A way to avoid this is the JobTracker to persist in DFS the completed jobs
> information upon job completion. This would be done at the time the job is
> moved to the completed jobs queue. Then when querying the JobTracker for
> information about a completed job, if it is not found in the memory queue, a
> lookup in DFS would be done to retrieve the completed job information.
> A directory in DFS (under mapred/system) would be used to persist completed
> job information, for each completed job there would be a directory with the
> job ID, within that directory all the information about the job: status,
> jobprofile, counters and completion events.
> A configuration property will indicate for how log persisted job information
> should be kept in DFS. After such period it will be cleaned up automatically.
> This improvement would not introduce API changes.
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