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From "mingleizhang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FLINK-4421) Make clocks and time measurements monotonous
Date Fri, 21 Jul 2017 02:46:00 GMT

    [ https://issues.apache.org/jira/browse/FLINK-4421?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16095699#comment-16095699
] 

mingleizhang commented on FLINK-4421:
-------------------------------------

Hi, Stephan. Thanks for reporting this. I would like to know, Under what circumstances will
lead to clock updates ? that is what you said can lead to negative duration. And I would like
to try read {{Introduce a Clock utility for monotonous system timestamps}}.

Like today I run a code like {{System.currentTimeMillis()}} return 12345. Tomorrow, I run
{{System.currentTimeMillis()}} return 12145. So, It can lead to negative duration.

> Make clocks and time measurements monotonous
> --------------------------------------------
>
>                 Key: FLINK-4421
>                 URL: https://issues.apache.org/jira/browse/FLINK-4421
>             Project: Flink
>          Issue Type: Improvement
>          Components: Core
>            Reporter: Stephan Ewen
>            Priority: Minor
>
> Currently, many places use {{System.currentTimeMillis()}} to acquire timestamps or measure
time intervals.
> Since this relies on the system clock, and the system clock is not necessarily monotonous
(in the presence of clock updates), this can lead to negative duration and decreasing timestamps
where increasing timestamps are expected.



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