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From "Arun C Murthy (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-2051) JobTracker's TaskCommitQueue is vulnerable to non-IOExceptions
Date Mon, 15 Oct 2007 10:38:50 GMT

    [ 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*

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. 

> 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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