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https://issues.apache.org/jira/browse/MAPREDUCE-4464?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13463991#comment-13463991
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Harsh J commented on MAPREDUCE-4464:
------------------------------------
>From test-patch on branch-1:
{code}
[exec] -1 overall.
[exec]
[exec] +1 @author. The patch does not contain any @author tags.
[exec]
[exec] -1 tests included. The patch doesn't appear to include any new
or modified tests.
[exec] Please justify why no tests are needed for
this patch.
[exec]
[exec] +1 javadoc. The javadoc tool did not generate any warning
messages.
[exec]
[exec] +1 javac. The applied patch does not increase the total number
of javac compiler warnings.
[exec]
[exec] -1 findbugs. The patch appears to introduce 220 new Findbugs
(version 2.0.1-rc3) warnings.
{code}
The 220 new findbugs from version 2.0.1-rc3 is what we get when the findbugs
target is run on the patch-less branch-1. Doesn't look like there are any
existing test-cases to cover this from an initial look. Also, the method in
which we'll be throwing this exception, already grants it via a "throws
IOException" agreement.
I ran -Dtestcase=TestMR* and -Dtestcase=TestMap* to run some MR tests over
branch-1 and they seem to pass with this applied.
+1 for committing. Just gonna run one job over a cluster instance with a
hostname with an underscore before doing so, to make sure this is working
reliably well.
> 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
> Assignee: Clint Heath
> Priority: Minor
> Attachments: MAPREDUCE-4464_new.patch, MAPREDUCE-4464.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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