pgandhi999 commented on a change in pull request #22806: [SPARK-25250][CORE] :
Late zombie task completions handled correctly even before new taskset launched
URL: https://github.com/apache/spark/pull/22806#discussion_r247217162
##########
File path:
core/src/main/scala/org/apache/spark/scheduler/TaskSchedulerImpl.scala
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@@ -286,6 +286,44 @@ private[spark] class TaskSchedulerImpl(
}
}
+ /**
+ * SPARK-25250: Whenever any Task gets successfully completed, we simply
mark the
+ * corresponding partition id as completed in all attempts for that
particular stage and
+ * additionally, for a Result Stage, we also kill the remaining task
attempts running on the
+ * same partition. As a result, we do not see any Killed tasks due to
+ * TaskCommitDenied Exceptions showing up in the UI. When this method is
called from
+ * DAGScheduler.scala on a task completion event being fired, it is assumed
that the new
+ * TaskSet has already been created and registered. However, a small
possibility does exist
+ * that when this method gets called, possibly the new TaskSet might have
not been added
Review comment:
Yes, indeed, this patch covers this corner case. But as @Ngone51 pointed
out, there is an extremely rare chance that when this method gets called from
DAGScheduler.scala, it could be possible that the new TaskSet might have not
been added to taskSetsByStageIdAndAttempt. My assumption while writing this
code was that there is always a small delay for the task completion event to
propagate to the DAGScheduler, which gives sufficient time for the new TaskSet
to be created gracefully. I have tested this patch like a million times and
have not once encountered this case, but theoretically, there might be a small
chance nevertheless. That is why I have added the comment, in case, somebody
encounters this in the future.
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