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https://issues.apache.org/jira/browse/SPARK-26817?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16762926#comment-16762926
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Thincrs commented on SPARK-26817:
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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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