Merge branch 'wip-3281-NullMessage-∂π'

akka-actor/src/main/scala/akka/actor/ActorCell.scala

@@ -6,7 +6,6 @@ package akka.actor
 
 import akka.actor.dungeon.ChildrenContainer
 import akka.dispatch.Envelope
-import akka.dispatch.NullMessage
 import akka.dispatch.sysmsg._
 import akka.event.Logging.{ LogEvent, Debug, Error }
 import akka.japi.Procedure
@@ -462,8 +461,7 @@ private[akka] class ActorCell(
     checkReceiveTimeout // Reschedule receive timeout
   }
 
-  def autoReceiveMessage(msg: Envelope): Unit =
+  def autoReceiveMessage(msg: Envelope): Unit = {
-    if (msg.message != NullMessage) {
     if (system.settings.DebugAutoReceive)
       publish(Debug(self.path.toString, clazz(actor), "received AutoReceiveMessage " + msg))
 

akka-actor/src/main/scala/akka/actor/ActorRefProvider.scala

@@ -6,7 +6,7 @@ package akka.actor
 
 import scala.collection.immutable
 import akka.dispatch.sysmsg._
-import akka.dispatch.{ UnboundedMessageQueueSemantics, RequiresMessageQueue, NullMessage }
+import akka.dispatch.{ UnboundedMessageQueueSemantics, RequiresMessageQueue }
 import akka.routing._
 import akka.event._
 import akka.util.{ Switch, Helpers }
@@ -496,7 +496,6 @@ private[akka] class LocalActorRefProvider private[akka] (
 
     override def !(message: Any)(implicit sender: ActorRef = Actor.noSender): Unit = stopped.ifOff(message match {
       case null ⇒ throw new InvalidMessageException("Message is null")
-      case NullMessage ⇒ // do nothing
       case _    ⇒ log.error(s"$this received unexpected message [$message]")
     })
 

akka-actor/src/main/scala/akka/actor/dungeon/Dispatch.scala

@@ -9,7 +9,6 @@ import akka.dispatch.{ MessageDispatcher, Mailbox, Envelope }
 import akka.dispatch.sysmsg._
 import akka.event.Logging.Error
 import akka.util.Unsafe
-import akka.dispatch.NullMessage
 import akka.actor._
 import akka.serialization.SerializationExtension
 import scala.util.control.NonFatal
@@ -68,7 +67,6 @@ private[akka] trait Dispatch { this: ActorCell ⇒
     if (sendSupervise) {
       // ➡➡➡ NEVER SEND THE SAME SYSTEM MESSAGE OBJECT TO TWO ACTORS ⬅⬅⬅
       parent.sendSystemMessage(akka.dispatch.sysmsg.Supervise(self, async = false))
-      parent ! NullMessage // read ScalaDoc of NullMessage to see why
     }
     this
   }

akka-actor/src/main/scala/akka/actor/dungeon/FaultHandling.scala

@@ -202,7 +202,6 @@ private[akka] trait FaultHandling { this: ActorCell ⇒
     catch handleNonFatalOrInterruptedException { e ⇒ publish(Error(e, self.path.toString, clazz(a), e.getMessage)) }
     finally try dispatcher.detach(this)
     finally try parent.sendSystemMessage(DeathWatchNotification(self, existenceConfirmed = true, addressTerminated = false))
-    finally try parent ! NullMessage // read ScalaDoc of NullMessage to see why
     finally try tellWatchersWeDied(a)
     finally try unwatchWatchedActors(a) // stay here as we expect an emergency stop from handleInvokeFailure
     finally {

akka-actor/src/main/scala/akka/dispatch/AbstractDispatcher.scala

@@ -27,21 +27,6 @@ object Envelope {
   }
 }
 
-/**
- * This message is sent directly after the Supervise system message in order
- * to form a barrier wrt. the first real message sent by the child, so that e.g.
- * Failed() cannot overtake Supervise(). Processing this does nothing.
- *
- * Detailed explanation:
- *
- * The race happens because Supervise and Failed may be queued between the
- * parent's check for system messages and dequeue(). Thus, if the parent
- * processes the NullMessage first (by way of that tiny race window), it is
- * guaranteed to then find the Supervise system message in its mailbox prior
- * to turning its attention to the next real message.
- */
-case object NullMessage extends AutoReceivedMessage
-
 final case class TaskInvocation(eventStream: EventStream, runnable: Runnable, cleanup: () ⇒ Unit) extends Batchable {
   final override def isBatchable: Boolean = runnable match {
     case b: Batchable                           ⇒ b.isBatchable

akka-cluster/src/multi-jvm/scala/akka/cluster/MultiNodeClusterSpec.scala

@@ -114,7 +114,6 @@ trait MultiNodeClusterSpec extends Suite with STMultiNodeSpec with WatchedByCoro
         classOf[InternalClusterAction.Tick],
         classOf[akka.actor.PoisonPill],
         classOf[akka.dispatch.sysmsg.DeathWatchNotification],
-        akka.dispatch.NullMessage.getClass,
         akka.remote.transport.AssociationHandle.Disassociated.getClass,
         akka.remote.transport.ActorTransportAdapter.DisassociateUnderlying.getClass,
         classOf[akka.remote.transport.AssociationHandle.InboundPayload])(sys)

akka-remote/src/test/scala/akka/remote/RemoteWatcherSpec.scala

@@ -93,8 +93,7 @@ class RemoteWatcherSpec extends AkkaSpec(
 
   Seq(system, remoteSystem).foreach(muteDeadLetters(
     akka.remote.transport.AssociationHandle.Disassociated.getClass,
-    akka.remote.transport.ActorTransportAdapter.DisassociateUnderlying.getClass,
+    akka.remote.transport.ActorTransportAdapter.DisassociateUnderlying.getClass)(_))
-    akka.dispatch.NullMessage.getClass)(_))
 
   override def afterTermination() {
     remoteSystem.shutdown()