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From "Vinod K V (JIRA)" <j...@apache.org>
Subject [jira] Updated: (HADOOP-5516) TaskMemoryManagerThread crashes in a corner case
Date Tue, 17 Mar 2009 11:32:58 GMT

     [ https://issues.apache.org/jira/browse/HADOOP-5516?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Vinod K V updated HADOOP-5516:

    Attachment: HADOOP-5516-1.txt

This seems to happen when ProcfsBasedProcessTree.getProcessTree() when the root process is
no longer alive. Attaching a patch for branch-0.20. This does the following:
 - When the root process is not found, getProcessTree() method returns an empty process-tree.
 - Added another null check in the same method when we cannot read process information from
/proc vfs.
 - Surrounded the memory management code of a single task with a try-catch block so that MemoryManager
thread continues to function on other tasks even in the event of occurrence of uncaught exceptions
on one task.
 - Removed a spurious HashMap.put() inside an iterator on the same map processTreeInfoMap
. This was pointed out by Hemanth.
 - Modified test-case to verify that method calls on ProcfsBasedProcessTree are sane even
if the process-tree is not alive or is gone.

> TaskMemoryManagerThread crashes in a corner case
> ------------------------------------------------
>                 Key: HADOOP-5516
>                 URL: https://issues.apache.org/jira/browse/HADOOP-5516
>             Project: Hadoop Core
>          Issue Type: Bug
>          Components: mapred
>    Affects Versions: 0.20.0
>            Reporter: Vinod K V
>            Assignee: Vinod K V
>            Priority: Blocker
>         Attachments: HADOOP-5516-1.txt
> TT's stdout says.
> {code}
> Exception in thread "org.apache.hadoop.mapred.TaskMemoryManagerThread" java.lang.NullPointerException
>         at org.apache.hadoop.util.ProcfsBasedProcessTree.getProcessTree(ProcfsBasedProcessTree.java:126)
>         at org.apache.hadoop.mapred.TaskMemoryManagerThread.run(TaskMemoryManagerThread.java:200)
> {code}
> TaskMemoryManager crashes and no further memory management is done.

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