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From "Tom White (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (MAPREDUCE-2421) Remove JobHistory's dependency on JobTracker
Date Fri, 27 May 2011 04:04:47 GMT

     [ https://issues.apache.org/jira/browse/MAPREDUCE-2421?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Tom White updated MAPREDUCE-2421:
---------------------------------

    Attachment: MAPREDUCE-2421.patch

I looked at extracting a JobsManager class, but the jobs map is deeply entangled in JobTracker,
and there's not a clean separation here. More importantly, from the point of view of this
JIRA it doesn't remove the dependency that JobHistory has on JobTracker. Replacing the dependency
on JobTracker with one on a JobManager class, which has a map of JobInProgress objects doesn't
help, since JobInProgess itself depends on JobTracker. So, unfortunately, this doesn't look
like a workable approach.

Instead I think the current patch is a reasonable solution - it's a standard technique of
using a callback interface to facilitate decoupling (a bit like TaskTrackerManager which exists
to make JobTracker more manageable for testing). I've regenerated the patch to mark the interface
as @Private @Unstable and added some javadoc so it's clearer what its purpose is.


> Remove JobHistory's dependency on JobTracker
> --------------------------------------------
>
>                 Key: MAPREDUCE-2421
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-2421
>             Project: Hadoop Map/Reduce
>          Issue Type: Sub-task
>          Components: client
>            Reporter: Tom White
>            Assignee: Tom White
>         Attachments: MAPREDUCE-2421.patch, MAPREDUCE-2421.patch
>
>
> The direct dependency can be removed by introducing a callback inteface. This is for
MAPREDUCE-1638. 

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