Need to send dummy hello message to actually estabilish akka connection.

yarn/2.0/src/main/scala/org/apache/spark/deploy/yarn/WorkerLauncher.scala

@@ -60,6 +60,8 @@ class WorkerLauncher(args: ApplicationMasterArguments, conf: Configuration) exte
     override def preStart() {
       logInfo("Listen to driver: " + driverUrl)
       driver = context.actorSelection(driverUrl)
+      // Send a hello message thus the connection is actually established, thus we can monitor Lifecycle Events.
+      driver ! "Hello"
       context.system.eventStream.subscribe(self, classOf[RemotingLifecycleEvent])
     }
 

yarn/2.2/src/main/scala/org/apache/spark/deploy/yarn/WorkerLauncher.scala

@@ -61,6 +61,8 @@ class WorkerLauncher(args: ApplicationMasterArguments, conf: Configuration) exte
     override def preStart() {
       logInfo("Listen to driver: " + driverUrl)
       driver = context.actorSelection(driverUrl)
+      // Send a hello message thus the connection is actually established, thus we can monitor Lifecycle Events.
+      driver ! "Hello"
       context.system.eventStream.subscribe(self, classOf[RemotingLifecycleEvent])
     }