[GitHub] MaxGekk opened a new pull request #23727: [SPARK-26817][CORE] Use System.nanoTime to measure time intervals

[GitBox <gi...@apache.org>]

MaxGekk opened a new pull request #23727: [SPARK-26817][CORE] Use System.nanoTime to measure time intervals
URL: https://github.com/apache/spark/pull/23727
 
 
   ## What changes were proposed in this pull request?
   
   In the PR, I propose to use `System.nanoTime()` instead of `System.currentTimeMillis()` in measurements of time intervals.
   
   `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.
   
   ## How was this patch tested?
   
   By existing test suites.
   

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