Enforce mailbox types on System actors. See #3273

akka-actor-tests/src/test/scala/akka/actor/ActorMailboxSpec.scala

@@ -102,7 +102,7 @@ class ActorMailboxSpec extends AkkaSpec(ActorMailboxSpec.mailboxConf) with Defau
 
     actor ! "ping"
     val q = expectMsgType[MessageQueue]
-    types foreach (t ⇒ assert(t isInstance q, s"Type [${q.getClass}] is not assignable to [${t}]"))
+    types foreach (t ⇒ assert(t isInstance q, s"Type [${q.getClass.getName}] is not assignable to [${t.getName}]"))
   }
 
   "An Actor" must {

akka-actor/src/main/resources/reference.conf

@@ -319,7 +319,15 @@ akka {
       # an instance of that actor its mailbox type will be decided by looking
       # up a mailbox configuration via T in this mapping
       requirements {
+        "akka.dispatch.UnboundedMessageQueueSemantics" = akka.actor.mailbox.unbounded-queue-based
         "akka.dispatch.DequeBasedMessageQueue" = akka.actor.mailbox.unbounded-deque-based
+        "akka.dispatch.UnboundedDequeBasedMessageQueueSemantics" = akka.actor.mailbox.unbounded-deque-based
+      }
+
+      unbounded-queue-based {
+        # FQCN of the MailboxType, The Class of the FQCN must have a public constructor
+        # with (akka.actor.ActorSystem.Settings, com.typesafe.config.Config) parameters.
+        mailbox-type = "akka.dispatch.UnboundedMailbox"
       }
 
       unbounded-deque-based {

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.NullMessage
+import akka.dispatch.{ UnboundedMessageQueueSemantics, RequiresMessageQueue, NullMessage }
 import akka.routing._
 import akka.event._
 import akka.util.{ Switch, Helpers }
@@ -367,7 +367,8 @@ private[akka] object LocalActorRefProvider {
   /*
    * Root and user guardian
    */
-  private class Guardian(override val supervisorStrategy: SupervisorStrategy) extends Actor {
+  private class Guardian(override val supervisorStrategy: SupervisorStrategy) extends Actor
+    with RequiresMessageQueue[UnboundedMessageQueueSemantics] {
 
     def receive = {
       case Terminated(_)    ⇒ context.stop(self)
@@ -382,7 +383,8 @@ private[akka] object LocalActorRefProvider {
   /**
    * System guardian
    */
-  private class SystemGuardian(override val supervisorStrategy: SupervisorStrategy, val guardian: ActorRef) extends Actor {
+  private class SystemGuardian(override val supervisorStrategy: SupervisorStrategy, val guardian: ActorRef)
+    extends Actor with RequiresMessageQueue[UnboundedMessageQueueSemantics] {
     import SystemGuardian._
 
     var terminationHooks = Set.empty[ActorRef]

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

@@ -3,7 +3,7 @@
  */
 package akka.actor
 
-import akka.dispatch.{ RequiresMessageQueue, Envelope, DequeBasedMessageQueue }
+import akka.dispatch.{ UnboundedDequeBasedMessageQueueSemantics, RequiresMessageQueue, Envelope, DequeBasedMessageQueue }
 import akka.AkkaException
 
 /**
@@ -47,8 +47,14 @@ import akka.AkkaException
  *  any trait/class that overrides the `preRestart` callback. This means it's not possible to write
  *  `Actor with MyActor with Stash` if `MyActor` overrides `preRestart`.
  */
-trait Stash extends Actor with RequiresMessageQueue[DequeBasedMessageQueue] {
+trait Stash extends UnrestrictedStash with RequiresMessageQueue[DequeBasedMessageQueue]
 
+/**
+ * The `UnboundedStash` trait is a version of `Stash` that enforces an unbounded stash for you actor.
+ */
+trait UnboundedStash extends UnrestrictedStash with RequiresMessageQueue[UnboundedDequeBasedMessageQueueSemantics]
+
+trait UnrestrictedStash extends Actor {
   /* The private stash of the actor. It is only accessible using `stash()` and
    * `unstashAll()`.
    */
@@ -68,12 +74,12 @@ trait Stash extends Actor with RequiresMessageQueue[DequeBasedMessageQueue] {
   private val mailbox: DequeBasedMessageQueue = {
     context.asInstanceOf[ActorCell].mailbox.messageQueue match {
       case queue: DequeBasedMessageQueue ⇒ queue
-      case other ⇒ throw ActorInitializationException(self, "DequeBasedMailbox required, got: " + other.getClass() + """
+      case other ⇒ throw ActorInitializationException(self, s"DequeBasedMailbox required, got: ${other.getClass.getName}\n" +
-An (unbounded) deque-based mailbox can be configured as follows:
+        """An (unbounded) deque-based mailbox can be configured as follows:
-  my-custom-dispatcher {
+          |  my-custom-mailbox {
-    mailbox-type = "akka.dispatch.UnboundedDequeBasedMailbox"
+          |    mailbox-type = "akka.dispatch.UnboundedDequeBasedMailbox"
-  }
+          |  }
-""")
+          |""".stripMargin)
     }
   }
 

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

@@ -31,3 +31,8 @@ package akka.actor
  * </pre>
  */
 abstract class UntypedActorWithStash extends UntypedActor with Stash
+
+/**
+ * Actor base class that enforces an unbounded stash for the actor.
+ */
+abstract class UntypedActorWithUnboundedStash extends UntypedActor with UnboundedStash

akka-actor/src/main/scala/akka/io/SelectionHandler.scala

@@ -19,6 +19,7 @@ import akka.io.IO.HasFailureMessage
 import akka.util.Helpers.Requiring
 import akka.event.LoggingAdapter
 import akka.util.SerializedSuspendableExecutionContext
+import akka.dispatch.{ UnboundedMessageQueueSemantics, RequiresMessageQueue }
 
 abstract class SelectionHandlerSettings(config: Config) {
   import config._
@@ -56,7 +57,8 @@ private[io] object SelectionHandler {
   case object WriteInterest
 }
 
-private[io] class SelectionHandler(settings: SelectionHandlerSettings) extends Actor with ActorLogging {
+private[io] class SelectionHandler(settings: SelectionHandlerSettings) extends Actor with ActorLogging
+  with RequiresMessageQueue[UnboundedMessageQueueSemantics] {
   import SelectionHandler._
   import settings._
 

akka-actor/src/main/scala/akka/io/TcpConnection.scala

@@ -17,14 +17,17 @@ import akka.util.ByteString
 import akka.io.Inet.SocketOption
 import akka.io.Tcp._
 import akka.io.SelectionHandler._
+import akka.dispatch.{ UnboundedMessageQueueSemantics, RequiresMessageQueue }
 
 /**
  * Base class for TcpIncomingConnection and TcpOutgoingConnection.
  *
  * INTERNAL API
  */
-private[io] abstract class TcpConnection(val channel: SocketChannel,
+private[io] abstract class TcpConnection(
-                                         val tcp: TcpExt) extends Actor with ActorLogging {
+  val channel: SocketChannel,
+  val tcp: TcpExt)
+  extends Actor with ActorLogging with RequiresMessageQueue[UnboundedMessageQueueSemantics] {
   import tcp.Settings._
   import tcp.bufferPool
   import TcpConnection._

akka-actor/src/main/scala/akka/io/TcpListener.scala

@@ -12,6 +12,7 @@ import akka.io.SelectionHandler._
 import akka.io.Tcp._
 import akka.io.IO.HasFailureMessage
 import java.net.InetSocketAddress
+import akka.dispatch.{ UnboundedMessageQueueSemantics, RequiresMessageQueue }
 
 /**
  * INTERNAL API
@@ -29,10 +30,12 @@ private[io] object TcpListener {
 /**
  * INTERNAL API
  */
-private[io] class TcpListener(val selectorRouter: ActorRef,
+private[io] class TcpListener(
+  val selectorRouter: ActorRef,
   val tcp: TcpExt,
   val bindCommander: ActorRef,
-                              val bind: Bind) extends Actor with ActorLogging {
+  val bind: Bind)
+  extends Actor with ActorLogging with RequiresMessageQueue[UnboundedMessageQueueSemantics] {
   import TcpListener._
   import tcp.Settings._
   import bind._

akka-actor/src/main/scala/akka/io/TcpPipelineHandler.scala

@@ -13,6 +13,7 @@ import scala.util.Failure
 import akka.actor.Terminated
 import akka.actor.Props
 import akka.util.ByteString
+import akka.dispatch.{ UnboundedMessageQueueSemantics, RequiresMessageQueue }
 
 object TcpPipelineHandler {
 
@@ -87,7 +88,7 @@ class TcpPipelineHandler[Ctx <: PipelineContext, Cmd, Evt](
   init: TcpPipelineHandler.Init[Ctx, Cmd, Evt],
   connection: ActorRef,
   handler: ActorRef)
-  extends Actor {
+  extends Actor with RequiresMessageQueue[UnboundedMessageQueueSemantics] {
 
   import init._
   import TcpPipelineHandler._

akka-actor/src/main/scala/akka/io/UdpConnection.scala

@@ -12,13 +12,16 @@ import java.nio.channels.DatagramChannel
 import java.nio.channels.SelectionKey._
 import scala.annotation.tailrec
 import scala.util.control.NonFatal
+import akka.dispatch.{ UnboundedMessageQueueSemantics, RequiresMessageQueue }
 
 /**
  * INTERNAL API
  */
-private[io] class UdpConnection(val udpConn: UdpConnectedExt,
+private[io] class UdpConnection(
+  val udpConn: UdpConnectedExt,
   val commander: ActorRef,
-                                val connect: Connect) extends Actor with ActorLogging {
+  val connect: Connect)
+  extends Actor with ActorLogging with RequiresMessageQueue[UnboundedMessageQueueSemantics] {
 
   def selector: ActorRef = context.parent
 

akka-actor/src/main/scala/akka/io/UdpListener.scala

@@ -13,14 +13,16 @@ import java.nio.channels.DatagramChannel
 import java.nio.channels.SelectionKey._
 import scala.annotation.tailrec
 import scala.util.control.NonFatal
+import akka.dispatch.{ UnboundedMessageQueueSemantics, RequiresMessageQueue }
 
 /**
  * INTERNAL API
  */
-private[io] class UdpListener(val udp: UdpExt,
+private[io] class UdpListener(
+  val udp: UdpExt,
   val bindCommander: ActorRef,
   val bind: Bind)
-  extends Actor with ActorLogging with WithUdpSend {
+  extends Actor with ActorLogging with WithUdpSend with RequiresMessageQueue[UnboundedMessageQueueSemantics] {
 
   import bind._
   import udp.bufferPool

akka-actor/src/main/scala/akka/io/UdpSender.scala

@@ -10,12 +10,16 @@ import akka.io.SelectionHandler.{ ChannelRegistered, RegisterChannel }
 import scala.collection.immutable
 import akka.io.Inet.SocketOption
 import scala.util.control.NonFatal
+import akka.dispatch.{ UnboundedMessageQueueSemantics, RequiresMessageQueue }
 
 /**
  * INTERNAL API
  */
-private[io] class UdpSender(val udp: UdpExt, options: immutable.Traversable[SocketOption], val commander: ActorRef)
+private[io] class UdpSender(
-  extends Actor with ActorLogging with WithUdpSend {
+  val udp: UdpExt,
+  options: immutable.Traversable[SocketOption],
+  val commander: ActorRef)
+  extends Actor with ActorLogging with WithUdpSend with RequiresMessageQueue[UnboundedMessageQueueSemantics] {
 
   def selector: ActorRef = context.parent
 

akka-cluster/src/main/scala/akka/cluster/ClusterDaemon.scala

@@ -16,6 +16,7 @@ import akka.actor.SupervisorStrategy.Stop
 import akka.cluster.MemberStatus._
 import akka.cluster.ClusterEvent._
 import akka.actor.ActorSelection
+import akka.dispatch.{ UnboundedMessageQueueSemantics, RequiresMessageQueue }
 
 /**
  * Base trait for all cluster messages. All ClusterMessage's are serializable.
@@ -175,7 +176,8 @@ private[cluster] object ClusterLeaderAction {
  *
  * Supervisor managing the different Cluster daemons.
  */
-private[cluster] final class ClusterDaemon(settings: ClusterSettings) extends Actor with ActorLogging {
+private[cluster] final class ClusterDaemon(settings: ClusterSettings) extends Actor with ActorLogging
+  with RequiresMessageQueue[UnboundedMessageQueueSemantics] {
   import InternalClusterAction._
   // Important - don't use Cluster(context.system) here because that would
   // cause deadlock. The Cluster extension is currently being created and is waiting
@@ -206,7 +208,8 @@ private[cluster] final class ClusterDaemon(settings: ClusterSettings) extends Ac
  * ClusterCoreDaemon and ClusterDomainEventPublisher can't be restarted because the state
  * would be obsolete. Shutdown the member if any those actors crashed.
  */
-private[cluster] final class ClusterCoreSupervisor extends Actor with ActorLogging {
+private[cluster] final class ClusterCoreSupervisor extends Actor with ActorLogging
+  with RequiresMessageQueue[UnboundedMessageQueueSemantics] {
   import InternalClusterAction._
 
   val publisher = context.actorOf(Props[ClusterDomainEventPublisher].
@@ -234,7 +237,8 @@ private[cluster] final class ClusterCoreSupervisor extends Actor with ActorLoggi
 /**
  * INTERNAL API.
  */
-private[cluster] final class ClusterCoreDaemon(publisher: ActorRef) extends Actor with ActorLogging {
+private[cluster] final class ClusterCoreDaemon(publisher: ActorRef) extends Actor with ActorLogging
+  with RequiresMessageQueue[UnboundedMessageQueueSemantics] {
   import ClusterLeaderAction._
   import InternalClusterAction._
 

akka-cluster/src/main/scala/akka/cluster/ClusterEvent.scala

@@ -11,6 +11,7 @@ import akka.cluster.ClusterEvent._
 import akka.cluster.MemberStatus._
 import akka.event.EventStream
 import akka.actor.AddressTerminated
+import akka.dispatch.{ UnboundedMessageQueueSemantics, RequiresMessageQueue }
 
 /**
  * Domain events published to the event bus.
@@ -252,7 +253,8 @@ object ClusterEvent {
  * Responsible for domain event subscriptions and publishing of
  * domain events to event bus.
  */
-private[cluster] final class ClusterDomainEventPublisher extends Actor with ActorLogging {
+private[cluster] final class ClusterDomainEventPublisher extends Actor with ActorLogging
+  with RequiresMessageQueue[UnboundedMessageQueueSemantics] {
   import InternalClusterAction._
 
   var latestGossip: Gossip = Gossip.empty

akka-cluster/src/main/scala/akka/cluster/ClusterReadView.scala

@@ -9,6 +9,7 @@ import scala.collection.immutable
 import akka.actor.{ Actor, ActorRef, ActorSystemImpl, Address, Props }
 import akka.cluster.ClusterEvent._
 import akka.actor.PoisonPill
+import akka.dispatch.{ UnboundedMessageQueueSemantics, RequiresMessageQueue }
 
 /**
  * INTERNAL API
@@ -40,7 +41,7 @@ private[akka] class ClusterReadView(cluster: Cluster) extends Closeable {
 
   // create actor that subscribes to the cluster eventBus to update current read view state
   private val eventBusListener: ActorRef = {
-    cluster.system.asInstanceOf[ActorSystemImpl].systemActorOf(Props(new Actor {
+    cluster.system.asInstanceOf[ActorSystemImpl].systemActorOf(Props(new Actor with RequiresMessageQueue[UnboundedMessageQueueSemantics] {
       override def preStart(): Unit = cluster.subscribe(self, classOf[ClusterDomainEvent])
       override def postStop(): Unit = cluster.unsubscribe(self)
 

akka-docs/rst/java/untyped-actors.rst

@@ -733,6 +733,12 @@ actor's state which have the same property. The :class:`Stash` trait’s
 implementation of :meth:`preRestart` will call ``unstashAll()``, which is
 usually the desired behavior.
 
+.. note::
+
+  If you want to enforce that your actor can only work with an unbounded stash,
+  then you should use the ``UntypedActorWithUnboundedStash`` class instead.
+
+
 .. _killing-actors-java:
 
 Killing an Actor

akka-docs/rst/scala/actors.rst

@@ -837,6 +837,12 @@ actor's state which have the same property. The :class:`Stash` trait’s
 implementation of :meth:`preRestart` will call ``unstashAll()``, which is
 usually the desired behavior.
 
+.. note::
+
+  If you want to enforce that your actor can only work with an unbounded stash,
+  then you should use the ``UnboundedStash`` trait instead.
+
+
 .. _killing-actors-scala:
 
 Killing an Actor

akka-multi-node-testkit/src/main/scala/akka/remote/testconductor/Player.scala

@@ -19,6 +19,7 @@ import akka.pattern.{ ask, pipe, AskTimeoutException }
 import akka.event.{ LoggingAdapter, Logging }
 import java.net.{ InetSocketAddress, ConnectException }
 import akka.remote.transport.ThrottlerTransportAdapter.{ SetThrottle, TokenBucket, Blackhole, Unthrottled }
+import akka.dispatch.{ UnboundedMessageQueueSemantics, RequiresMessageQueue }
 
 /**
  * The Player is the client component of the
@@ -49,7 +50,7 @@ trait Player { this: TestConductorExt ⇒
 
     if (_client ne null) throw new IllegalStateException("TestConductorClient already started")
     _client = system.actorOf(Props(classOf[ClientFSM], name, controllerAddr), "TestConductorClient")
-    val a = system.actorOf(Props(new Actor {
+    val a = system.actorOf(Props(new Actor with RequiresMessageQueue[UnboundedMessageQueueSemantics] {
       var waiting: ActorRef = _
       def receive = {
         case fsm: ActorRef ⇒
@@ -140,7 +141,8 @@ private[akka] object ClientFSM {
  *
  * INTERNAL API.
  */
-private[akka] class ClientFSM(name: RoleName, controllerAddr: InetSocketAddress) extends Actor with LoggingFSM[ClientFSM.State, ClientFSM.Data] {
+private[akka] class ClientFSM(name: RoleName, controllerAddr: InetSocketAddress) extends Actor
+  with LoggingFSM[ClientFSM.State, ClientFSM.Data] with RequiresMessageQueue[UnboundedMessageQueueSemantics] {
   import ClientFSM._
 
   val settings = TestConductor().Settings

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

@@ -390,7 +390,9 @@ private[remote] class EndpointWriter(
   codec: AkkaPduCodec,
   val refuseUid: Option[Int],
   val receiveBuffers: ConcurrentHashMap[Link, AckedReceiveBuffer[Message]],
-  val reliableDeliverySupervisor: Option[ActorRef]) extends EndpointActor(localAddress, remoteAddress, transport, settings, codec) with Stash with FSM[EndpointWriter.State, Unit] {
+  val reliableDeliverySupervisor: Option[ActorRef])
+  extends EndpointActor(localAddress, remoteAddress, transport, settings, codec) with UnboundedStash
+  with FSM[EndpointWriter.State, Unit] {
 
   import EndpointWriter._
   import context.dispatcher

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

@@ -17,6 +17,7 @@ import scala.concurrent.{ ExecutionContext, Future }
 import scala.concurrent.forkjoin.ThreadLocalRandom
 import com.typesafe.config.Config
 import akka.ConfigurationException
+import akka.dispatch.{ RequiresMessageQueue, UnboundedMessageQueueSemantics }
 
 /**
  * INTERNAL API
@@ -31,7 +32,8 @@ private[akka] object RemoteActorRefProvider {
   case object WaitTransportShutdown extends TerminatorState
   case object Finished extends TerminatorState
 
-  private class RemotingTerminator(systemGuardian: ActorRef) extends Actor with FSM[TerminatorState, Option[Internals]] {
+  private class RemotingTerminator(systemGuardian: ActorRef) extends Actor with FSM[TerminatorState, Option[Internals]]
+    with RequiresMessageQueue[UnboundedMessageQueueSemantics] {
     import context.dispatcher
 
     startWith(Uninitialized, None)

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

@@ -9,6 +9,7 @@ import akka.actor.Terminated
 import akka.actor.Actor
 import akka.actor.ActorRef
 import akka.dispatch.sysmsg.DeathWatchNotification
+import akka.dispatch.{ UnboundedMessageQueueSemantics, RequiresMessageQueue }
 
 /**
  * INTERNAL API
@@ -23,7 +24,7 @@ private[akka] object RemoteDeploymentWatcher {
  * Responsible for cleaning up child references of remote deployed actors when remote node
  * goes down (jvm crash, network failure), i.e. triggered by [[akka.actor.AddressTerminated]].
  */
-private[akka] class RemoteDeploymentWatcher extends Actor {
+private[akka] class RemoteDeploymentWatcher extends Actor with RequiresMessageQueue[UnboundedMessageQueueSemantics] {
   import RemoteDeploymentWatcher._
   var supervisors = Map.empty[ActorRef, InternalActorRef]
 

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

@@ -14,6 +14,7 @@ import akka.actor.RootActorPath
 import akka.actor.Terminated
 import akka.actor.ExtendedActorSystem
 import akka.ConfigurationException
+import akka.dispatch.{ UnboundedMessageQueueSemantics, RequiresMessageQueue }
 
 /**
  * INTERNAL API
@@ -92,7 +93,7 @@ private[akka] class RemoteWatcher(
   unreachableReaperInterval: FiniteDuration,
   heartbeatExpectedResponseAfter: FiniteDuration,
   numberOfEndHeartbeatRequests: Int)
-  extends Actor with ActorLogging {
+  extends Actor with ActorLogging with RequiresMessageQueue[UnboundedMessageQueueSemantics] {
 
   import RemoteWatcher._
   import context.dispatcher

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

@@ -23,6 +23,7 @@ import scala.util.control.NonFatal
 import scala.util.{ Failure, Success }
 import akka.remote.transport.AkkaPduCodec.Message
 import java.util.concurrent.ConcurrentHashMap
+import akka.dispatch.{ RequiresMessageQueue, UnboundedMessageQueueSemantics }
 
 /**
  * INTERNAL API
@@ -82,7 +83,7 @@ private[remote] object Remoting {
 
   case class RegisterTransportActor(props: Props, name: String)
 
-  private[Remoting] class TransportSupervisor extends Actor {
+  private[Remoting] class TransportSupervisor extends Actor with RequiresMessageQueue[UnboundedMessageQueueSemantics] {
     override def supervisorStrategy = OneForOneStrategy() {
       case NonFatal(e) ⇒ Restart
     }
@@ -348,7 +349,8 @@ private[remote] object EndpointManager {
 /**
  * INTERNAL API
  */
-private[remote] class EndpointManager(conf: Config, log: LoggingAdapter) extends Actor {
+private[remote] class EndpointManager(conf: Config, log: LoggingAdapter) extends Actor
+  with RequiresMessageQueue[UnboundedMessageQueueSemantics] {
 
   import EndpointManager._
   import context.dispatcher

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

@@ -12,7 +12,7 @@ import akka.util.Timeout
 import scala.collection.immutable
 import scala.concurrent.duration._
 import scala.concurrent.{ ExecutionContext, Promise, Future }
-import scala.util.Success
+import akka.dispatch.{ UnboundedMessageQueueSemantics, RequiresMessageQueue }
 
 trait TransportAdapterProvider {
   /**
@@ -162,7 +162,8 @@ abstract class ActorTransportAdapter(wrappedTransport: Transport, system: ActorS
   override def shutdown(): Unit = manager ! PoisonPill
 }
 
-abstract class ActorTransportAdapterManager extends Actor {
+abstract class ActorTransportAdapterManager extends Actor
+  with RequiresMessageQueue[UnboundedMessageQueueSemantics] {
   import ActorTransportAdapter.{ ListenUnderlying, ListenerRegistered }
 
   private var delayedEvents = immutable.Queue.empty[Any]

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

@@ -22,6 +22,7 @@ import scala.collection.immutable
 import scala.concurrent.duration._
 import scala.concurrent.{ Future, Promise }
 import scala.util.control.NonFatal
+import akka.dispatch.{ UnboundedMessageQueueSemantics, RequiresMessageQueue }
 
 @SerialVersionUID(1L)
 class AkkaProtocolException(msg: String, cause: Throwable) extends AkkaException(msg, cause) with OnlyCauseStackTrace {
@@ -227,7 +228,8 @@ private[transport] class ProtocolStateActor(initialData: InitialProtocolStateDat
                                             private val settings: AkkaProtocolSettings,
                                             private val codec: AkkaPduCodec,
                                             private val failureDetector: FailureDetector)
-  extends Actor with FSM[AssociationState, ProtocolStateData] {
+  extends Actor with FSM[AssociationState, ProtocolStateData]
+  with RequiresMessageQueue[UnboundedMessageQueueSemantics] {
 
   import ProtocolStateActor._
   import context.dispatcher

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

@@ -22,6 +22,7 @@ import scala.math.min
 import scala.util.{ Success, Failure }
 import scala.util.control.NonFatal
 import akka.dispatch.sysmsg.{ Unwatch, Watch }
+import akka.dispatch.{ UnboundedMessageQueueSemantics, RequiresMessageQueue }
 
 class ThrottlerProvider extends TransportAdapterProvider {
 
@@ -336,7 +337,8 @@ private[transport] class ThrottledAssociation(
   val associationHandler: AssociationEventListener,
   val originalHandle: AssociationHandle,
   val inbound: Boolean)
-  extends Actor with LoggingFSM[ThrottledAssociation.ThrottlerState, ThrottledAssociation.ThrottlerData] {
+  extends Actor with LoggingFSM[ThrottledAssociation.ThrottlerState, ThrottledAssociation.ThrottlerData]
+  with RequiresMessageQueue[UnboundedMessageQueueSemantics] {
   import ThrottledAssociation._
   import context.dispatcher
 

akka-zeromq/src/main/scala/akka/zeromq/ZeroMQExtension.scala

@@ -14,6 +14,7 @@ import java.util.concurrent.TimeUnit
 import akka.util.Timeout
 import org.zeromq.ZMQException
 import scala.concurrent.duration.FiniteDuration
+import akka.dispatch.{ UnboundedMessageQueueSemantics, RequiresMessageQueue }
 
 /**
  * A Model to represent a version of the zeromq library
@@ -241,7 +242,7 @@ class ZeroMQExtension(system: ActorSystem) extends Extension {
   private val zeromqGuardian: ActorRef = {
     verifyZeroMQVersion()
 
-    system.actorOf(Props(new Actor {
+    system.actorOf(Props(new Actor with RequiresMessageQueue[UnboundedMessageQueueSemantics] {
       import SupervisorStrategy._
       override def supervisorStrategy = OneForOneStrategy() {
         case ex: ZMQException if nonfatal(ex) ⇒ Resume