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From "Dongjoon Hyun (JIRA)" <j...@apache.org>
Subject [jira] [Issue Comment Deleted] (SPARK-26817) Use System.nanoTime to measure time intervals
Date Fri, 08 Feb 2019 08:25:00 GMT

     [ https://issues.apache.org/jira/browse/SPARK-26817?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Dongjoon Hyun updated SPARK-26817:
----------------------------------
    Comment: was deleted

(was: A user of thincrs has selected this issue. Deadline: Thu, Feb 14, 2019 6:03 PM)

> Use System.nanoTime to measure time intervals
> ---------------------------------------------
>
>                 Key: SPARK-26817
>                 URL: https://issues.apache.org/jira/browse/SPARK-26817
>             Project: Spark
>          Issue Type: Improvement
>          Components: Spark Core
>    Affects Versions: 2.4.0
>            Reporter: Maxim Gekk
>            Priority: Minor
>
> Replace System.currentTimeMillis() by System.nanoTime in time intervals measurements.
System.currentTimeMillis() returns current wallclock time and will follow changes to the system
clock. Thus, negative wallclock adjustments can cause timeouts to "hang" for a long time (until
wallclock time has caught up to its previous value again). This can happen when ntpd does
a "step" after the network has been disconnected for some time. The most canonical example
is during system bootup when DHCP takes longer than usual. This can lead to failures that
are really hard to understand/reproduce. System.nanoTime() is guaranteed to be monotonically
increasing irrespective of wallclock changes.
>  
> https://github.com/databricks/scala-style-guide#prefer-nanotime-over-currenttimemillis



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