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

["Junping Du (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/MAPREDUCE-5940?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14051046#comment-14051046 ] 

Junping Du commented on MAPREDUCE-5940:
---------------------------------------

Thanks [~zjshen] to work on this and [~vvasudev] to review! This seems to be an interesting issue. I think a better/clean way to fix it is to update elapsed() method: If System.currentTimeMillis() < started, then we can return -1 or 0 instead (and log a warn that clock not getting synchronized). Thoughts?

> 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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