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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