[jira] [Updated] (MAPREDUCE-2421) Remove JobHistory's dependency on JobTracker

["Tom White (JIRA)" <ji...@apache.org>]

     [ 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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