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Date: Tue, 13 Nov 2012 00:39:12 +0000 (UTC)
From: "Karthik Kambatla (JIRA)" <jira@apache.org>
To: yarn-issues@hadoop.apache.org
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Subject: [jira] [Commented] (YARN-164) Race condition in Fair Scheduler
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    [ https://issues.apache.org/jira/browse/YARN-164?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13495791#comment-13495791 ] 

Karthik Kambatla commented on YARN-164:
---------------------------------------

Nice catch. I have a minor comment: {{updateThread.start()}} should probably be in a try-catch, and catch should set {{initialized}} to false. Otherwise, +1
                
> Race condition in Fair Scheduler
> --------------------------------
>
>                 Key: YARN-164
>                 URL: https://issues.apache.org/jira/browse/YARN-164
>             Project: Hadoop YARN
>          Issue Type: Bug
>          Components: scheduler
>    Affects Versions: 2.0.2-alpha
>            Reporter: Devaraj K
>            Assignee: Devaraj K
>            Priority: Critical
>         Attachments: YARN-164.patch
>
>
> {code:xml}
>       Thread updateThread = new Thread(new UpdateThread());
>       updateThread.start();
>       initialized = true;
> {code}
> In the above code, making the initialized as true after starting the UpdateThread.
> {code:xml}
>   private class UpdateThread implements Runnable {
>     public void run() {
>       while (initialized) {
>         try {
>           Thread.sleep(UPDATE_INTERVAL);
>           update();
>           preemptTasksIfNecessary();
>         } catch (Exception e) {
>           LOG.error("Exception in fair scheduler UpdateThread", e);
>         }
>       }
>     }
>   }
>  {code}
>  In this run method of UpdateThread, it is checking for the initialized and exiting if it is not true. Here most of the times initialized is getting true after exiting the UpdateThread and the thread functionality is missing, due to that all the submitted applications are hanging without making any progress.

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