!rem #3765: Change the defaults for remoting

- removed retry-window and related settings
 - removed gate-invalid-addresses-for
 - gate is now mandatory
 - remoting has a dedicated dispatcher by default
 - updated tests to work with changed timings
 - added doc section for association lifecycle

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

@@ -187,12 +187,10 @@ private[remote] class ReliableDeliverySupervisor(
   val transport: AkkaProtocolTransport,
   val settings: RemoteSettings,
   val codec: AkkaPduCodec,
-  val receiveBuffers: ConcurrentHashMap[Link, ResendState]) extends Actor {
+  val receiveBuffers: ConcurrentHashMap[Link, ResendState]) extends Actor with ActorLogging {
   import ReliableDeliverySupervisor._
   import context.dispatcher
 
-  def retryGateEnabled = settings.RetryGateClosedFor > Duration.Zero
-
   var autoResendTimer: Option[Cancellable] = None
 
   def scheduleAutoResend(): Unit = if (resendBuffer.nacked.nonEmpty || resendBuffer.nonAcked.nonEmpty) {
@@ -206,20 +204,18 @@ private[remote] class ReliableDeliverySupervisor(
     scheduleAutoResend()
   }
 
-  override val supervisorStrategy = OneForOneStrategy(settings.MaximumRetriesInWindow, settings.RetryWindow, loggingEnabled = false) {
+  override val supervisorStrategy = OneForOneStrategy(loggingEnabled = false) {
     case e @ (_: AssociationProblem) ⇒ Escalate
     case NonFatal(e) ⇒
+      log.warning("Association with remote system [{}] has failed, address is now gated for [{}] ms. Reason is: [{}].",
+        remoteAddress, settings.RetryGateClosedFor.toMillis, e.getMessage)
       uidConfirmed = false // Need confirmation of UID again
-      if (retryGateEnabled) {
-        context.become(gated)
-        context.system.scheduler.scheduleOnce(settings.RetryGateClosedFor, self, Ungate)
-        context.unwatch(writer)
-        currentHandle = None
-        context.parent ! StoppedReading(self)
-        Stop
-      } else {
-        Restart
-      }
+      context.become(gated)
+      context.system.scheduler.scheduleOnce(settings.RetryGateClosedFor, self, Ungate)
+      context.unwatch(writer)
+      currentHandle = None
+      context.parent ! StoppedReading(self)
+      Stop
   }
 
   var currentHandle: Option[AkkaProtocolHandle] = handleOrActive