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https://issues.apache.org/jira/browse/MAPREDUCE-323?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12874758#action_12874758
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Dick King commented on MAPREDUCE-323:
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If the cluster configuration codes any time stamps, we have to create them.
We'll do this the first time we make a filename for a given job.
Having done that, we'll have a map mapping job serial numbers to directory
segments [which we will intern; there will be many duplicates].
Having done _that_, we will we'll keep 250K of these; we'll drop the oldest one
when we add a new one that would otherwise add more than that. We'll therefore
use a {{TreeMap}} . I expect about 20-40 bytes per entry; 16 bytes each tree
node, and 8 or 16 for the key which would be an {{Integer}} . Recall that the
directory segments are interned and would essentially vanish.
This table only exists if there is a time stamp operator in the format string.
> Improve the way job history files are managed
> ---------------------------------------------
>
> Key: MAPREDUCE-323
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-323
> Project: Hadoop Map/Reduce
> Issue Type: Bug
> Components: jobtracker
> Affects Versions: 0.21.0, 0.22.0
> Reporter: Amar Kamat
> Assignee: Dick King
> Priority: Critical
>
> Today all the jobhistory files are dumped in one _job-history_ folder. This
> can cause problems when there is a need to search the history folder
> (job-recovery etc). It would be nice if we group all the jobs under a _user_
> folder. So all the jobs for user _amar_ will go in _history-folder/amar/_.
> Jobs can be categorized using various features like _jobid, date, jobname_
> etc but using _username_ will make the search much more efficient and also
> will not result into namespace explosion.
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