mridulm commented on a change in pull request #35719:
URL: https://github.com/apache/spark/pull/35719#discussion_r818967642
##########
File path: core/src/main/scala/org/apache/spark/MapOutputTracker.scala
##########
@@ -1022,101 +1022,105 @@ private[spark] class MapOutputTrackerMaster(
if (preferredLoc.nonEmpty) {
preferredLoc
} else {
- if (shuffleLocalityEnabled && dep.rdd.partitions.length <
SHUFFLE_PREF_MAP_THRESHOLD &&
- dep.partitioner.numPartitions < SHUFFLE_PREF_REDUCE_THRESHOLD) {
- val blockManagerIds = getLocationsWithLargestOutputs(dep.shuffleId,
partitionId,
- dep.partitioner.numPartitions, REDUCER_PREF_LOCS_FRACTION)
- if (blockManagerIds.nonEmpty) {
- blockManagerIds.get.map(_.host)
- } else {
- Nil
- }
- } else {
- Nil
- }
+ getLocationsWithLargestOutputs(
+ dep,
+ 0,
+ dep.rdd.getNumPartitions,
+ partitionId,
+ partitionId + 1,
+ REDUCER_PREF_LOCS_FRACTION).map(_.host)
}
} else {
Nil
}
}
/**
- * Return a list of locations that each have fraction of map output greater
than the specified
- * threshold.
+ * Return the preferred hosts on which to run the given map output partition
in a given shuffle,
+ * i.e. the nodes that the most outputs for that partition are on.
*
- * @param shuffleId id of the shuffle
- * @param reducerId id of the reduce task
- * @param numReducers total number of reducers in the shuffle
- * @param fractionThreshold fraction of total map output size that a
location must have
- * for it to be considered large.
+ * @param dep shuffle dependency object
+ * @param startMapIndex the start map index (inclusive)
+ * @param endMapIndex the end map index (exclusive)
+ * @param startReducerIndex the start reducer index (inclusive)
+ * @param endReducerIndex the end reducer index (exclusive)
+ * @return a sequence of locations where task runs.
*/
- def getLocationsWithLargestOutputs(
- shuffleId: Int,
- reducerId: Int,
- numReducers: Int,
- fractionThreshold: Double)
- : Option[Array[BlockManagerId]] = {
-
- val shuffleStatus = shuffleStatuses.get(shuffleId).orNull
- if (shuffleStatus != null) {
- shuffleStatus.withMapStatuses { statuses =>
- if (statuses.nonEmpty) {
- // HashMap to add up sizes of all blocks at the same location
- val locs = new HashMap[BlockManagerId, Long]
- var totalOutputSize = 0L
- var mapIdx = 0
- while (mapIdx < statuses.length) {
- val status = statuses(mapIdx)
- // status may be null here if we are called between
registerShuffle, which creates an
- // array with null entries for each output, and
registerMapOutputs, which populates it
- // with valid status entries. This is possible if one thread
schedules a job which
- // depends on an RDD which is currently being computed by another
thread.
- if (status != null) {
- val blockSize = status.getSizeForBlock(reducerId)
- if (blockSize > 0) {
- locs(status.location) = locs.getOrElse(status.location, 0L) +
blockSize
- totalOutputSize += blockSize
- }
- }
- mapIdx = mapIdx + 1
- }
- val topLocs = locs.filter { case (loc, size) =>
- size.toDouble / totalOutputSize >= fractionThreshold
- }
- // Return if we have any locations which satisfy the required
threshold
- if (topLocs.nonEmpty) {
- return Some(topLocs.keys.toArray)
- }
- }
- }
- }
- None
+ def getPreferredLocationsForShuffle(
+ dep: ShuffleDependency[_, _, _],
+ startMapIndex: Int,
+ endMapIndex: Int,
+ startReducerIndex: Int,
+ endReducerIndex: Int): Seq[String] = {
+ getLocationsWithLargestOutputs(
+ dep,
+ startMapIndex,
+ endMapIndex,
+ startReducerIndex,
+ endReducerIndex,
+ REDUCER_PREF_LOCS_FRACTION).map(_.host)
}
/**
- * Return the locations where the Mappers ran. The locations each includes
both a host and an
- * executor id on that host.
+ * If shuffle locality is enabled, return a list of locations that each have
fraction of
+ * map output greater than the specified threshold.
*
* @param dep shuffle dependency object
- * @param startMapIndex the start map index
+ * @param startMapIndex the start map index (inclusive)
* @param endMapIndex the end map index (exclusive)
- * @return a sequence of locations where task runs.
+ * @param startReducerIndex the start reducer index (inclusive)
+ * @param endReducerIndex the end reducer index (exclusive)
+ * @param fractionThreshold fraction of total map output size that a
location must have
+ * for it to be considered large.
*/
- def getMapLocation(
+ def getLocationsWithLargestOutputs(
dep: ShuffleDependency[_, _, _],
startMapIndex: Int,
- endMapIndex: Int): Seq[String] =
- {
- val shuffleStatus = shuffleStatuses.get(dep.shuffleId).orNull
- if (shuffleStatus != null) {
- shuffleStatus.withMapStatuses { statuses =>
- if (startMapIndex < endMapIndex &&
- (startMapIndex >= 0 && endMapIndex <= statuses.length)) {
- val statusesPicked = statuses.slice(startMapIndex,
endMapIndex).filter(_ != null)
- statusesPicked.map(_.location.host).toSeq
- } else {
- Nil
+ endMapIndex: Int,
+ startReducerIndex: Int,
+ endReducerIndex: Int,
+ fractionThreshold: Double): Seq[BlockManagerId] = {
+ if (shuffleLocalityEnabled && dep.rdd.getNumPartitions <
SHUFFLE_PREF_MAP_THRESHOLD &&
+ dep.partitioner.numPartitions < SHUFFLE_PREF_REDUCE_THRESHOLD) {
+ val shuffleStatus = shuffleStatuses.get(dep.shuffleId).orNull
+ if (shuffleStatus != null) {
+ shuffleStatus.withMapStatuses { statuses =>
+ if (statuses.nonEmpty && startMapIndex < endMapIndex &&
+ startMapIndex >= 0 && endMapIndex <= statuses.length) {
+ // HashMap to add up sizes of all blocks at the same location
+ val locs = new HashMap[BlockManagerId, Long]
+ var totalOutputSize = 0L
+ var mapIdx = startMapIndex
Review comment:
Hmm, we need to enforce `fractionThreshold` as well ... ok, this might
not work.
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