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From "Alejandro Abdelnur (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (YARN-184) Remove unnecessary locking in fair scheduler, and address findbugs excludes.
Date Wed, 14 Nov 2012 05:32:13 GMT

    [ https://issues.apache.org/jira/browse/YARN-184?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13496873#comment-13496873
] 

Alejandro Abdelnur commented on YARN-184:
-----------------------------------------

*FairScheduler.java*

* The UpdateThread should be set as a daemon thread.

*QueueManager.java*

* At the end of the  reloadAllocs() method a synchronized block on THIS reassigns all resources
info/apps/weights/modes/.. values. But the getter methods of those values are not synchronized,
ie getUserMaxApp() which could lead to an inconsistent result. A solution would be to have
a struct that defines all the instance Maps, make that volatile, assign it atomically and
on the getter methods assign it to a local var and then access all its values from the local
var (if a reassign happens half way you still have a consistent view of all values you use)

                
> Remove unnecessary locking in fair scheduler, and address findbugs excludes.
> ----------------------------------------------------------------------------
>
>                 Key: YARN-184
>                 URL: https://issues.apache.org/jira/browse/YARN-184
>             Project: Hadoop YARN
>          Issue Type: Improvement
>    Affects Versions: 2.0.2-alpha
>            Reporter: Sandy Ryza
>            Assignee: Sandy Ryza
>         Attachments: YARN-184-1.patch, YARN-184.patch
>
>
> In YARN-12, locks were added to all fields of QueueManager to address findbugs.  In addition,
findbugs exclusions were added in response to MAPREDUCE-4439, without a deep look at the code.

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