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https://issues.apache.org/jira/browse/MAPREDUCE-4464?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Clint Heath updated MAPREDUCE-4464:
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Attachment: MAPREDUCE-4464_new.patch
I have just attached the new patch which throws an IO Exception instead. Would
it be possible to request that this JIRA be assigned to me? I'd like to get
this resolved as quickly as possible. Thank you.
> Reduce tasks failing with NullPointerException in ConcurrentHashMap.get()
> -------------------------------------------------------------------------
>
> Key: MAPREDUCE-4464
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-4464
> Project: Hadoop Map/Reduce
> Issue Type: Bug
> Components: task
> Affects Versions: 1.0.0
> Reporter: Clint Heath
> Priority: Minor
> Attachments: MAPREDUCE-4464.patch, MAPREDUCE-4464_new.patch
>
> Original Estimate: 1h
> Remaining Estimate: 1h
>
> If DNS does not resolve hostnames properly, reduce tasks can fail with a very
> misleading exception.
> as per my peer Ahmed's diagnosis:
> In ReduceTask, it seems that event.getTaskTrackerHttp() returns a malformed
> URI, and so host from:
> {code}
> String host = u.getHost();
> {code}
> is evaluated to null and the NullPointerException is thrown afterwards in the
> ConcurrentHashMap.
> I have written a patch to check for a null hostname condition when getHost is
> called in the getMapCompletionEvents method and print an intelligible warning
> message rather than suppressing it until later when it becomes confusing and
> misleading.
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