Shutdown of transports are now synchronous with system shutdown #3368

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

@@ -126,26 +126,23 @@ private[remote] class Remoting(_system: ExtendedActorSystem, _provider: RemoteAc
     endpointManager match {
       case Some(manager) ⇒
         implicit val timeout = ShutdownTimeout
-        val stopped: Future[Boolean] = (manager ? ShutdownAndFlush).mapTo[Boolean]
 
         def finalize(): Unit = {
           eventPublisher.notifyListeners(RemotingShutdownEvent)
           endpointManager = None
         }
 
-        stopped.onComplete {
+        (manager ? ShutdownAndFlush).mapTo[Boolean].andThen {
           case Success(flushSuccessful) ⇒
             if (!flushSuccessful)
-              log.warning("Shutdown finished, but flushing timed out. Some messages might not have been sent. " +
+              log.warning("Shutdown finished, but flushing might not have been successful and some messages might have been dropped. " +
                 "Increase akka.remote.flush-wait-on-shutdown to a larger value to avoid this.")
             finalize()
 
           case Failure(e) ⇒
             notifyError("Failure during shutdown of remoting.", e)
             finalize()
-        }
+        } map { _ ⇒ () } // RARP needs only type Unit, not a boolean
-
-        stopped map { _ ⇒ () } // RARP needs only type Unit, not a boolean
       case None ⇒
         log.warning("Remoting is not running. Ignoring shutdown attempt.")
         Future successful (())
@@ -526,12 +523,20 @@ private[remote] class EndpointManager(conf: Config, log: LoggingAdapter) extends
       endpoints.prune()
     case ShutdownAndFlush ⇒
       // Shutdown all endpoints and signal to sender when ready (and whether all endpoints were shut down gracefully)
-      val sys = context.system // Avoid closing over context
+
-      Future sequence endpoints.allEndpoints.map {
+      def shutdownAll[T](resources: TraversableOnce[T])(shutdown: T ⇒ Future[Boolean]): Future[Boolean] = {
-        gracefulStop(_, settings.FlushWait, EndpointWriter.FlushAndStop)
+        (Future sequence resources.map(shutdown(_))) map { _.foldLeft(true) { _ && _ } } recover {
-      } map { _.foldLeft(true) { _ && _ } } recover {
+          case NonFatal(_) ⇒ false
-        case _: AskTimeoutException ⇒ false
+        }
-      } pipeTo sender
+      }
+
+      (for {
+        // The construction of the future for shutdownStatus has to happen after the flushStatus future has been finished
+        // so that endpoints are shut down before transports.
+        flushStatus ← shutdownAll(endpoints.allEndpoints)(gracefulStop(_, settings.FlushWait, EndpointWriter.FlushAndStop))
+        shutdownStatus ← shutdownAll(transportMapping.values)(_.shutdown())
+      } yield flushStatus && shutdownStatus) pipeTo sender
+
       // Ignore all other writes
       context.become(flushing)
   }
@@ -623,12 +628,6 @@ private[remote] class EndpointManager(conf: Config, log: LoggingAdapter) extends
 
   override def postStop(): Unit = {
     pruneTimerCancellable.foreach { _.cancel() }
-    transportMapping.values foreach { transport ⇒
-      try transport.shutdown() catch {
-        case NonFatal(e) ⇒
-          log.error(e, s"Unable to shut down the underlying transport: [$transport]")
-      }
-    }
   }
 
 }

akka-remote/src/main/scala/akka/remote/transport/AbstractTransportAdapter.scala

@@ -4,7 +4,7 @@
 package akka.remote.transport
 
 import akka.actor._
-import akka.pattern.{ ask, pipe }
+import akka.pattern.{ ask, pipe, gracefulStop }
 import akka.remote.Remoting.RegisterTransportActor
 import akka.remote.transport.Transport._
 import akka.remote.RARP
@@ -97,7 +97,7 @@ abstract class AbstractTransportAdapter(protected val wrappedTransport: Transpor
     statusPromise.future
   }
 
-  override def shutdown(): Unit = wrappedTransport.shutdown()
+  override def shutdown(): Future[Boolean] = wrappedTransport.shutdown()
 
 }
 
@@ -159,7 +159,11 @@ abstract class ActorTransportAdapter(wrappedTransport: Transport, system: ActorS
   override def interceptAssociate(remoteAddress: Address, statusPromise: Promise[AssociationHandle]): Unit =
     manager ! AssociateUnderlying(remoteAddress, statusPromise)
 
-  override def shutdown(): Unit = manager ! PoisonPill
+  override def shutdown(): Future[Boolean] =
+    for {
+      stopResult ← gracefulStop(manager, RARP(system).provider.remoteSettings.FlushWait)
+      wrappedStopResult ← wrappedTransport.shutdown()
+    } yield stopResult && wrappedStopResult
 }
 
 abstract class ActorTransportAdapterManager extends Actor

akka-remote/src/main/scala/akka/remote/transport/AkkaProtocolTransport.scala

@@ -141,10 +141,6 @@ private[transport] class AkkaProtocolManager(
   private def createTransportFailureDetector(): FailureDetector =
     FailureDetectorLoader(settings.TransportFailureDetectorImplementationClass, settings.TransportFailureDetectorConfig)
 
-  override def postStop() {
-    wrappedTransport.shutdown()
-  }
-
 }
 
 private[remote] class AkkaProtocolHandle(

akka-remote/src/main/scala/akka/remote/transport/TestTransport.scala

@@ -86,7 +86,7 @@ class TestTransport(
     (localHandle, remoteHandle)
   }
 
-  private def defaultShutdown: Future[Unit] = Future.successful(())
+  private def defaultShutdown: Future[Boolean] = Future.successful(true)
 
   /**
    * The [[akka.remote.transport.TestTransport.SwitchableLoggedBehavior]] for the listen() method.
@@ -105,13 +105,13 @@ class TestTransport(
   /**
    * The [[akka.remote.transport.TestTransport.SwitchableLoggedBehavior]] for the shutdown() method.
    */
-  val shutdownBehavior = new SwitchableLoggedBehavior[Unit, Unit](
+  val shutdownBehavior = new SwitchableLoggedBehavior[Unit, Boolean](
     (_) ⇒ defaultShutdown,
     (_) ⇒ registry.logActivity(ShutdownAttempt(localAddress)))
 
   override def listen: Future[(Address, Promise[AssociationEventListener])] = listenBehavior(())
   override def associate(remoteAddress: Address): Future[AssociationHandle] = associateBehavior(remoteAddress)
-  override def shutdown(): Unit = shutdownBehavior(())
+  override def shutdown(): Future[Boolean] = shutdownBehavior(())
 
   private def defaultWrite(params: (TestAssociationHandle, ByteString)): Future[Boolean] = {
     registry.getRemoteReadHandlerFor(params._1) match {

akka-remote/src/main/scala/akka/remote/transport/ThrottlerTransportAdapter.scala

@@ -198,8 +198,6 @@ private[transport] class ThrottlerManager(wrappedTransport: Transport) extends A
 
   private def nakedAddress(address: Address): Address = address.copy(protocol = "", system = "")
 
-  override def postStop(): Unit = wrappedTransport.shutdown()
-
   override def ready: Receive = {
     case InboundAssociation(handle) ⇒
       val wrappedHandle = wrapHandle(handle, associationListener, inbound = true)

akka-remote/src/main/scala/akka/remote/transport/Transport.scala

@@ -119,12 +119,14 @@ trait Transport {
   def associate(remoteAddress: Address): Future[AssociationHandle]
 
   /**
-   * Shuts down the transport layer and releases all the corresponding resources. Shutdown is asynchronous, may be
+   * Shuts down the transport layer and releases all the corresponding resources. Shutdown is asynchronous signalling
-   * called multiple times and does not return a success indication.
+   * the end of the shutdown by completing the returned future.
    *
    * The transport SHOULD try flushing pending writes before becoming completely closed.
+   * @return
+   *   Future signalling the completion of shutdown
    */
-  def shutdown(): Unit
+  def shutdown(): Future[Boolean]
 
   /**
    * This method allows upper layers to send management commands to the transport. It is the responsibility of the

akka-remote/src/main/scala/akka/remote/transport/netty/NettyTransport.scala

@@ -417,14 +417,15 @@ class NettyTransport(val settings: NettyTransportSettings, val system: ExtendedA
     }
   }
 
-  override def shutdown(): Unit = {
+  override def shutdown(): Future[Boolean] = {
-    def always(c: ChannelGroupFuture) = NettyFutureBridge(c) recover { case _ ⇒ c.getGroup }
+    def always(c: ChannelGroupFuture) = NettyFutureBridge(c).map(_ ⇒ true) recover { case _ ⇒ false }
     for {
       // Force flush by trying to write an empty buffer and wait for success
-      _ ← always(channelGroup.write(ChannelBuffers.buffer(0)))
+      lastWriteStatus ← always(channelGroup.write(ChannelBuffers.buffer(0)))
-      _ ← always({ channelGroup.unbind(); channelGroup.disconnect() })
+      unbindStatus ← always(channelGroup.unbind())
-      _ ← always(channelGroup.close())
+      disconnectStatus ← always(channelGroup.disconnect())
-    } {
+      closeStatus ← always(channelGroup.close())
+    } yield {
       // Release the selectors, but don't try to kill the dispatcher
       if (UseDispatcherForIo.isDefined) {
         clientChannelFactory.shutdown()
@@ -433,6 +434,7 @@ class NettyTransport(val settings: NettyTransportSettings, val system: ExtendedA
         clientChannelFactory.releaseExternalResources()
         serverChannelFactory.releaseExternalResources()
       }
+      lastWriteStatus && unbindStatus && disconnectStatus && closeStatus
     }
 
   }