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Date: Wed, 27 Aug 2014 21:14:59 +0000 (UTC)
From: "Vinod Kumar Vavilapalli (JIRA)" <jira@apache.org>
To: yarn-issues@hadoop.apache.org
Message-ID: <JIRA.12725957.1404804955388.26945.1409174099643@arcas>
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References: <JIRA.12725957.1404804955388@arcas>
Subject: [jira] [Commented] (YARN-2327) YARN should warn about nodes with
 poor clock synchronization
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    [ 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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