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From "Vinod Kumar Vavilapalli (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (YARN-2327) YARN should warn about nodes with poor clock synchronization
Date Wed, 27 Aug 2014 21:14:59 GMT

    [ https://issues.apache.org/jira/browse/YARN-2327?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14112861#comment-14112861
] 

Vinod Kumar Vavilapalli commented on YARN-2327:
-----------------------------------------------

YARN itself depends on clock sync today for token-expiry to work. RM doles out a container-token
at time T, and AM hands this off to the NM which then makes sure that {{T + token-expiry-interval
(defaulting to 10mins) <= current-time}}.

Clearly this assumes that the clocks are synchronized. We can continue to assume the same
given the assumption's pervasive nature and warn accordingly. If that is not acceptable, we
can slightly improve this to only assume that the clocks proceed at the same rate if not out
right synchronized.

> YARN should warn about nodes with poor clock synchronization
> ------------------------------------------------------------
>
>                 Key: YARN-2327
>                 URL: https://issues.apache.org/jira/browse/YARN-2327
>             Project: Hadoop YARN
>          Issue Type: Bug
>            Reporter: Zhijie Shen
>
> YARN should warn about nodes with poor clock synchronization.
> YARN relies on approximate clock synchronization to report certain elapsed time statistics
(see YARN-2251), but we currently don't warn if this assumption is violated.



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