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Posted to mapreduce-issues@hadoop.apache.org by "Zhijie Shen (JIRA)" <ji...@apache.org> on 2014/06/25 07:42:24 UTC

[jira] [Commented] (MAPREDUCE-5940) Avoid negative elapsed time in JHS/MRAM web UI and services

    [ https://issues.apache.org/jira/browse/MAPREDUCE-5940?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14043061#comment-14043061 ] 

Zhijie Shen commented on MAPREDUCE-5940:
----------------------------------------

I'll file a separate Jira about the global clock synchronization issue, and introduce the possible problem to result in negative elapsed time.

> Avoid negative elapsed time in JHS/MRAM web UI and services
> -----------------------------------------------------------
>
>                 Key: MAPREDUCE-5940
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-5940
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>          Components: jobhistoryserver, mr-am, webapps
>            Reporter: Zhijie Shen
>            Assignee: Zhijie Shen
>         Attachments: MAPREDUCE-5940.1.patch
>
>
> Recently we observed a rare bug that an elapsed time of a reducer is going to be negative on JHS web UI and via REST APIs. While the real reason for this bug seems to be clock asynchronization on different hosts, the web frontend should have masked the negative values. However, in the current code, *org.apache.hadoop.mapreduce.v2.app.webapp.dao.** only check whether the elapsed time is -1 or not.



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