Mailing-List: contact mapreduce-issues-help@hadoop.apache.org; run by ezmlm
Precedence: bulk
Reply-To: mapreduce-issues@hadoop.apache.org
Date: Thu, 27 Sep 2012 01:13:07 +1100 (NCT)
From: "Clint Heath (JIRA)" <jira@apache.org>
To: mapreduce-issues@hadoop.apache.org
Message-ID: <681268084.128448.1348668787968.JavaMail.jiratomcat@arcas>
In-Reply-To: <20036562.77190.1342721794955.JavaMail.jiratomcat@issues-vm>
Subject: [jira] [Commented] (MAPREDUCE-4464) Reduce tasks failing with
 NullPointerException in ConcurrentHashMap.get()
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 7bit


    [ https://issues.apache.org/jira/browse/MAPREDUCE-4464?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13463842#comment-13463842 ] 

Clint Heath commented on MAPREDUCE-4464:
----------------------------------------

Thanks Harsh!  I'll take a look at yarn and see if a similar situation is present there.
                
> 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.

--
This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators
For more information on JIRA, see: http://www.atlassian.com/software/jira