venkata91 commented on a change in pull request #30164:
URL: https://github.com/apache/spark/pull/30164#discussion_r518402471
##########
File path:
resource-managers/yarn/src/main/scala/org/apache/spark/scheduler/cluster/YarnSchedulerBackend.scala
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@@ -161,6 +170,27 @@ private[spark] abstract class YarnSchedulerBackend(
totalRegisteredExecutors.get() >= totalExpectedExecutors *
minRegisteredRatio
}
+ override def getMergerLocations(
+ numPartitions: Int,
+ resourceProfileId: Int): Seq[BlockManagerId] = {
+ // Currently this is naive way of calculating numMergersNeeded for a
stage. In future,
+ // we can use better heuristics to calculate numMergersNeeded for a stage.
+ val tasksPerExecutor = sc.resourceProfileManager
+ .resourceProfileFromId(resourceProfileId).maxTasksPerExecutor(sc.conf)
+ val numMergersNeeded = math.min(
+ math.max(1, math.ceil(numPartitions / tasksPerExecutor).toInt),
maxNumExecutors)
+ val minMergersThreshold = math.max(minMergersStaticThreshold,
+ math.floor(numMergersNeeded * minMergersThresholdRatio).toInt)
Review comment:
> So if numMergersNeeded=3 and minMergersThreshold=5 and mergers
returned from BlockManagerMaster is 100, you want to return the 100 mergers
here? If so, it doesn't look reasonable.
In that case would only request `numMergersNeeded` mergers to
`BlockManagerMaster` which is `3` not `100`. Let me know if this clarifies it
or not.
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