Github user tgravescs commented on a diff in the pull request:
https://github.com/apache/spark/pull/12113#discussion_r58536056
--- Diff: core/src/main/scala/org/apache/spark/MapOutputTracker.scala ---
@@ -296,10 +290,89 @@ private[spark] class MapOutputTrackerMaster(conf:
SparkConf)
protected val mapStatuses = new ConcurrentHashMap[Int,
Array[MapStatus]]().asScala
private val cachedSerializedStatuses = new ConcurrentHashMap[Int,
Array[Byte]]().asScala
+ private val maxRpcMessageSize = RpcUtils.maxMessageSizeBytes(conf)
+
+ // Kept in sync with cachedSerializedStatuses explicitly
+ // This is required so that the Broadcast variable remains in scope
until we remove
+ // the shuffleId explicitly or implicitly.
+ private val cachedSerializedBroadcast = new HashMap[Int,
Broadcast[Array[Byte]]]()
+
+ // This is to prevent multiple serializations of the same shuffle -
which happens when
+ // there is a request storm when shuffle start.
+ private val shuffleIdLocks = new ConcurrentHashMap[Int, AnyRef]()
+
+ // requests for map output statuses
+ private val mapOutputRequests = new
LinkedBlockingQueue[GetMapOutputMessage]
+
+ // Thread pool used for handling map output status requests. This is a
separate thread pool
+ // to ensure we don't block the normal dispatcher threads.
+ private val threadpool: ThreadPoolExecutor = {
+ val numThreads =
conf.getInt("spark.shuffle.mapOutput.dispatcher.numThreads", 8)
+ val pool = ThreadUtils.newDaemonFixedThreadPool(numThreads,
"map-output-dispatcher")
+ for (i <- 0 until numThreads) {
+ pool.execute(new MessageLoop)
+ }
+ pool
+ }
+
+ def post(message: GetMapOutputMessage): Unit = {
+ mapOutputRequests.offer(message)
+ }
+
+ /** Message loop used for dispatching messages. */
+ private class MessageLoop extends Runnable {
+ override def run(): Unit = {
+ try {
+ while (true) {
+ try {
+ val data = mapOutputRequests.take()
+ if (data == PoisonPill) {
+ // Put PoisonPill back so that other MessageLoops can see it.
+ mapOutputRequests.offer(PoisonPill)
+ return
+ }
+ val context = data.context
+ val shuffleId = data.shuffleId
+ val hostPort = context.senderAddress.hostPort
+ logDebug("Handling request to send map output locations for
shuffle " + shuffleId +
+ " to " + hostPort)
+ val mapOutputStatuses =
getSerializedMapOutputStatuses(shuffleId)
--- End diff --
Are you saying 7 additional seconds on top of the serialization?
if so you can try increasing the number of threads or obviously increasing
the timeout. What is your timeout set at? Generally I've found that any job
that large I have to increase the timeouts on it anyway.
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