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From "Dick King (JIRA)" <j...@apache.org>
Subject [jira] Commented: (MAPREDUCE-323) Improve the way job history files are managed
Date Wed, 02 Jun 2010 19:34:43 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-323?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12874758#action_12874758
] 

Dick King commented on MAPREDUCE-323:
-------------------------------------

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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