From 1ae3c0fc5e0273319d0e9497268a4c9854aae2e0 Mon Sep 17 00:00:00 2001
From: Prashant Sharma <scrapcodes@gmail.com>
Date: Sat, 14 Dec 2013 10:44:24 +0530
Subject: [PATCH] Added a comment about ActorRef and ActorSelection difference.
---
.../src/main/scala/org/apache/spark/MapOutputTracker.scala | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/core/src/main/scala/org/apache/spark/MapOutputTracker.scala b/core/src/main/scala/org/apache/spark/MapOutputTracker.scala
index fbda11f578..10fae5af9f 100644
--- a/core/src/main/scala/org/apache/spark/MapOutputTracker.scala
+++ b/core/src/main/scala/org/apache/spark/MapOutputTracker.scala
@@ -72,6 +72,13 @@ private[spark] class MapOutputTracker extends Logging {
// throw a SparkException if this fails.
private def askTracker(message: Any): Any = {
try {
+ /*
+ The difference between ActorRef and ActorSelection is well explained here:
+ http://doc.akka.io/docs/akka/2.2.3/project/migration-guide-2.1.x-2.2.x.html#Use_actorSelection_instead_of_actorFor
+ In spark a map output tracker can be either started on Driver where it is created which
+ is an ActorRef or it can be on executor from where it is looked up which is an
+ actorSelection.
+ */
val future = trackerActor match {
case Left(a: ActorRef) => a.ask(message)(timeout)
case Right(b: ActorSelection) => b.ask(message)(timeout)
--
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