[jira] [Commented] (SPARK-26817) Use System.nanoTime to measure time intervals

["Thincrs (JIRA)" <ji...@apache.org>]

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

Thincrs commented on SPARK-26817:
---------------------------------

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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