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From "Amar Kamat (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-4670) Improve the way job history files are managed
Date Tue, 18 Nov 2008 10:19:44 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-4670?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12648565#action_12648565
] 

Amar Kamat commented on HADOOP-4670:
------------------------------------

Doug, the search is w.r.t job-recovery. The type of search we do there is given a _jobtracker-hostname,
job-id, username and job-name_ search the job-history file. The way we do it now is 
- construct a regex using _jobtracker-hostname, job-id, username and job-name_
- construct a path filter that accepts files that match the pattern and reject otherwise
- use the dfs listing api to find out files matching the pattern

This is a costly operation as all the files are scanned linearly. Over time the history folder
can grow big leading to more search time. The only problem is all the users will be hit with
this. With the above mentioned optimization we can reduce the search time for most of the
users.

> Improve the way job history files are managed
> ---------------------------------------------
>
>                 Key: HADOOP-4670
>                 URL: https://issues.apache.org/jira/browse/HADOOP-4670
>             Project: Hadoop Core
>          Issue Type: Improvement
>          Components: mapred
>    Affects Versions: 0.20.0
>            Reporter: Amar Kamat
>            Assignee: Amar Kamat
>             Fix For: 0.20.0
>
>
> 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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