- Removed usage of null from Endpoint

- Fixed race resolution logic in FailureDetectorRegistry to not create unnecessary instances

akka-remote/src/main/scala/akka/remote/Endpoint.scala

@@ -93,8 +93,9 @@ private[remote] object EndpointWriter {
   /**
    * This message signals that the current association maintained by the local EndpointWriter and EndpointReader is
    * to be overridden by a new inbound association. This is needed to avoid parallel inbound associations from the
-   * same remote endpoint.
-   * @param handle
+   * same remote endpoint: when a parallel inbound association is detected, the old one is removed and the new one is
+   * used instead.
+   * @param handle Handle of the new inbound association.
    */
   case class TakeOver(handle: AssociationHandle)
   case object BackoffTimer
@@ -130,7 +131,7 @@ private[remote] class EndpointWriter(
   override val supervisorStrategy = OneForOneStrategy() { case NonFatal(e) ⇒ publishAndThrow(e) }
 
   val msgDispatch =
-    new DefaultMessageDispatcher(extendedSystem, extendedSystem.provider.asInstanceOf[RemoteActorRefProvider], log)
+    new DefaultMessageDispatcher(extendedSystem, RARP(extendedSystem).provider, log)
 
   def inbound = handle.isDefined
 
@@ -238,8 +239,12 @@ private[remote] class EndpointWriter(
 
   private def startReadEndpoint(): Unit = handle match {
     case Some(h) ⇒
-      reader = Some(context.watch(context.actorOf(Props(new EndpointReader(codec, h.localAddress, msgDispatch)),
-        "endpointReader-" + URLEncoder.encode(remoteAddress.toString, "utf-8") + "-" + readerId.next())))
+      val readerLocalAddress = h.localAddress
+      val readerCodec = codec
+      val readerDispatcher = msgDispatch
+      reader = Some(
+        context.watch(context.actorOf(Props(new EndpointReader(readerCodec, readerLocalAddress, readerDispatcher)),
+          "endpointReader-" + URLEncoder.encode(remoteAddress.toString, "utf-8") + "-" + readerId.next())))
       h.readHandlerPromise.success(reader.get)
     case None ⇒ throw new EndpointException("Internal error: No handle was present during creation of the endpoint" +
       "reader.", null)
@@ -261,7 +266,7 @@ private[remote] class EndpointReader(
   val localAddress: Address,
   val msgDispatch: InboundMessageDispatcher) extends Actor {
 
-  val provider = context.system.asInstanceOf[ExtendedActorSystem].provider.asInstanceOf[RemoteActorRefProvider]
+  val provider = RARP(context.system).provider
 
   override def receive: Receive = {
     case Disassociated ⇒ context.stop(self)