mridulm commented on a change in pull request #33896:
URL: https://github.com/apache/spark/pull/33896#discussion_r743376778
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File path: core/src/main/scala/org/apache/spark/scheduler/DAGScheduler.scala
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@@ -1716,7 +1739,31 @@ private[spark] class DAGScheduler(
if (runningStages.contains(shuffleStage) &&
shuffleStage.pendingPartitions.isEmpty) {
if (!shuffleStage.shuffleDep.shuffleMergeFinalized &&
shuffleStage.shuffleDep.getMergerLocs.nonEmpty) {
- scheduleShuffleMergeFinalize(shuffleStage)
+ // Check if a finalize task has already been scheduled. This
is to prevent the
+ // following scenario: Stage A attempt 0 fails and gets
retried. Stage A attempt 1
+ // succeeded, triggering the scheduling of shuffle merge
finalization. However,
+ // tasks from Stage A attempt 0 might still be running and
sending task completion
+ // events to DAGScheduler. This check prevents multiple
attempts to schedule merge
+ // finalization get triggered due to this.
+ if (shuffleStage.shuffleDep.getFinalizeTask.isEmpty) {
+ // If total shuffle size is smaller than the threshold,
attempt to immediately
+ // schedule shuffle merge finalization and process map stage
completion.
+ val totalSize = Try(mapOutputTracker
+
.getStatistics(shuffleStage.shuffleDep).bytesByPartitionId.sum).getOrElse(0L)
+ if (totalSize < shuffleMergeWaitMinSizeThreshold) {
+ // Check if we can process map stage completion. If
shuffle merge finalization
+ // is already triggered because push completion ratio was
reached earlier,
+ // we cannot process map stage completion, but have to
wait for the finalization
+ // to finish. This is because it's not straightforward to
interrupt the
+ // finalization task and undo what it might have already
done.
+ if (scheduleShuffleMergeFinalize(shuffleStage, delay = 0,
+ registerMergeResults = false)) {
+ handleShuffleMergeFinalized(shuffleStage)
Review comment:
Yes, this should not happen - the codepath just confused me.
Particularly, there is no way currently `scheduleShuffleMergeFinalize`
returns false in this path right now.
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