[GitHub] [spark] vanzin commented on a change in pull request #26058: [SPARK-10614][core] Add monotonic time to Clock interface.

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

vanzin commented on a change in pull request #26058: [SPARK-10614][core] Add monotonic time to Clock interface.
URL: https://github.com/apache/spark/pull/26058#discussion_r332686468
 
 

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 File path: core/src/main/scala/org/apache/spark/ExecutorAllocationManager.scala
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 @@ -288,7 +288,7 @@ private[spark] class ExecutorAllocationManager(
     }
 
     // Update executor target number only after initializing flag is unset
-    updateAndSyncNumExecutorsTarget(clock.getTimeMillis())
+    updateAndSyncNumExecutorsTarget(clock.nanoTime())
 
 Review comment:
   Are you sure about that?
   
   This is what the javadocs say:
   
       The same origin is used by all invocations of this method in an instance of a Java virtual
       machine; other virtual machine instances are likely to use a different origin. 
   
   (Comment about "other virtual machines" aside.)
   
   That seems to be corroborated by other sources, too (e.g. https://stackoverflow.com/questions/510462/is-system-nanotime-completely-useless). Seems in a long gone past there might have been issues, but not today.

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