xleoken commented on code in PR #2119:
URL:
https://github.com/apache/incubator-celeborn/pull/2119#discussion_r1413278837
##########
master/src/main/scala/org/apache/celeborn/service/deploy/master/Master.scala:
##########
@@ -666,23 +666,32 @@ private[celeborn] class Master(
val shuffleKey = Utils.makeShuffleKey(requestSlots.applicationId,
requestSlots.shuffleId)
val availableWorkers = workersAvailable()
+ // reply false if all workers are unavailable
+ if (availableWorkers.isEmpty) {
+ logError(
+ s"Non available workers, offer slots for $numReducers reducers of
$shuffleKey failed!")
+ context.reply(RequestSlotsResponse(StatusCode.SLOT_NOT_AVAILABLE, new
WorkerResource()))
+ return
+ }
+
val numAvailableWorkers = availableWorkers.size()
val numWorkers = Math.min(
Math.max(
if (requestSlots.shouldReplicate) 2 else 1,
if (requestSlots.maxWorkers <= 0) slotsAssignMaxWorkers
else Math.min(slotsAssignMaxWorkers, requestSlots.maxWorkers)),
numAvailableWorkers)
+
+ // We treated availableWorkers as a Circular Queue here.
val startIndex = Random.nextInt(numAvailableWorkers)
+ val endIndex = startIndex + numWorkers
+
val selectedWorkers = new util.ArrayList[WorkerInfo](numWorkers)
- selectedWorkers.addAll(availableWorkers.subList(
- startIndex,
- Math.min(numAvailableWorkers, startIndex + numWorkers)))
- if (startIndex + numWorkers > numAvailableWorkers) {
- selectedWorkers.addAll(availableWorkers.subList(
- 0,
- startIndex + numWorkers - numAvailableWorkers))
+ for (index <- startIndex until endIndex) {
+ val realIndex = index % numAvailableWorkers
+ selectedWorkers.add(availableWorkers.get(realIndex))
}
+
Review Comment:
hi @mridulm, thanks for your detail response 👍, you are very correct about
the algorithm performance itself, but the focus of this patch is to improve
readability, and we can see that there is a similar algorithm in the
`Master#handleRequestSlots`
https://github.com/apache/incubator-celeborn/blob/1c7cd1bd1392c8d3fd4396c539696dc79835f8dc/master/src/main/scala/org/apache/celeborn/service/deploy/master/Master.scala#L738-L750
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