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Date: Mon, 15 Oct 2007 03:38:50 -0700 (PDT)
From: "Arun C Murthy (JIRA)" <jira@apache.org>
To: hadoop-dev@lucene.apache.org
Subject: [jira] Commented: (HADOOP-2051) JobTracker's TaskCommitQueue is
 vulnerable to non-IOExceptions
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    [ https://issues.apache.org/jira/browse/HADOOP-2051?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12534796 ] 

Arun C Murthy commented on HADOOP-2051:
---------------------------------------

FindBugs is complaining that I'm catching Exception, which is precisely the point of this jira. *smile*

{noformat}
REC_CATCH_EXCEPTION: Exception is caught when Exception is not thrown

This method uses a try-catch block that catches Exception objects, but Exception is not thrown within the try block, and RuntimeException is not explicitly caught. 
It is a common bug pattern to say try { ... } catch (Exception e) { something } as a shorthand for catching a number of types of exception each of whose catch blocks is identical, but this construct also accidentally catches RuntimeException as well, masking potential bugs. 
{noformat}

> JobTracker's TaskCommitQueue is vulnerable to non-IOExceptions
> --------------------------------------------------------------
>
>                 Key: HADOOP-2051
>                 URL: https://issues.apache.org/jira/browse/HADOOP-2051
>             Project: Hadoop
>          Issue Type: Bug
>          Components: mapred
>    Affects Versions: 0.15.0
>            Reporter: Arun C Murthy
>            Assignee: Arun C Murthy
>            Priority: Blocker
>             Fix For: 0.15.0
>
>         Attachments: HADOOP-2051_1_20071013.patch
>
>
> The {{JobTracker#TaskCommitQueue#run}} method only handles {{IOException}}s. Christian Kunz ran into a scenario where a job was stuck with all tasks in {{COMMIT_PENDING}} state and the stack traces showed that the "Task Commit Thread" wasn't even around.
> The work-around is to model {{TaskCommitQueue#run}} along the lines of other long-running threads in the {{JobTracer}} ({{ExpireLaunchingTasks}}, {{ExpireTrackers}} etc.) to catch, log and ignore any {{Exception}} in a loop.

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