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https://issues.apache.org/jira/browse/HADOOP-1876?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12557292#action_12557292
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Runping Qi commented on HADOOP-1876:
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I am fine with the approach of this patch if it turns out to be simpler than
using JobHistory.
Can this patch make JobHistory log obsolete? Or at least is that intended?
I hate to see same information logged at different places
in different forms using different code paths.
Other than being in text format (which has its pros and cons), job history log
is event based,
from which you can construct the whole execution history of a job and derive
various time-series data
such as number of mappers/reducers of different states (waiting, running,
sorting, shuffling, completed, etc)
This kind of information if important for understanding the runtime behavior of
the job.
If RunningJob can easily accomodate those kinds of time series data, then I am
OK to obsolete job history log.
Also, have folks considered the relationship between this and HADOOP-2178?
> 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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