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From "Vinod K V (JIRA)" <j...@apache.org>
Subject [jira] Commented: (MAPREDUCE-1136) ConcurrentModificationException when tasktracker updates task status to jobtracker
Date Mon, 02 Nov 2009 04:44:59 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-1136?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12772416#action_12772416
] 

Vinod K V commented on MAPREDUCE-1136:
--------------------------------------

bq. Is this because the access to jobs is not synchronized?
Yes

bq. Wouldn't this result in losing a heartbeat? 
No, the RPC in question is getAllJobs(), so no case of missing heartbeat. At-least not in
this case.


> ConcurrentModificationException when tasktracker updates task status to jobtracker
> ----------------------------------------------------------------------------------
>
>                 Key: MAPREDUCE-1136
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-1136
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>          Components: tasktracker
>    Affects Versions: 0.20.2, 0.21.0, 0.22.0
>            Reporter: Qi Liu
>
> In Hadoop 0.18.3, the following exception happened during a job execution. It does not
happen often.
> Here is the stack trace of the exception.
> org.apache.hadoop.ipc.RemoteException: java.io.IOException: java.util.ConcurrentModificationException
>         at java.util.TreeMap$PrivateEntryIterator.nextEntry(TreeMap.java:1100)
>         at java.util.TreeMap$ValueIterator.next(TreeMap.java:1145)
>         at org.apache.hadoop.mapred.JobTracker.getAllJobs(JobTracker.java:2376)
>         at sun.reflect.GeneratedMethodAccessor32.invoke(Unknown Source)
>         at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
>         at java.lang.reflect.Method.invoke(Method.java:597)
>         at org.apache.hadoop.ipc.RPC$Server.call(RPC.java:481)
>         at org.apache.hadoop.ipc.Server$Handler.run(Server.java:890)
>  org.apache.hadoop.ipc.Client.call(Client.java:716)

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