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From "Devaraj K (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (MAPREDUCE-5940) Avoid negative elapsed time in JHS/MRAM web UI and services
Date Thu, 03 Jul 2014 05:15:25 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-5940?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14051073#comment-14051073
] 

Devaraj K commented on MAPREDUCE-5940:
--------------------------------------

Silently making the elapsed time as 0 when it is negative may lead to hiding the bugs related
to elapsed time. Adding a warning/info message before making it as 0 would help to diagnose/find
out the issues if any.

> 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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