Support same dispatcher as parent in Typed, #27123 (#27127)

* Support same dispatcher as parent in Typed, #27123

* remove apply in internal DispatcherDefault and DispatcherSameAsParent

akka-actor-typed-tests/src/test/java/akka/actor/typed/DispatcherSelectorTest.java

@@ -10,4 +10,5 @@ public class DispatcherSelectorTest {
 
   private DispatcherSelector def = DispatcherSelector.defaultDispatcher();
   private DispatcherSelector conf = DispatcherSelector.fromConfig("somepath");
+  private DispatcherSelector parent = DispatcherSelector.sameAsParent();
 }

akka-actor-typed-tests/src/test/java/jdocs/akka/typed/DispatchersDocTest.java

@@ -26,6 +26,7 @@ public class DispatchersDocTest {
                 yourBehavior,
                 "DispatcherFromConfig",
                 DispatcherSelector.fromConfig("your-dispatcher"));
+            context.spawn(yourBehavior, "ParentDispatcher", DispatcherSelector.sameAsParent());
             // #spawn-dispatcher
 
             return Behaviors.same();

akka-actor-typed-tests/src/test/scala/akka/actor/typed/PropsSpec.scala

@@ -9,7 +9,7 @@ import org.scalatest.WordSpec
 
 class PropsSpec extends WordSpec with Matchers {
 
-  val dispatcherFirst = DispatcherDefault(DispatcherFromConfig("pool"))
+  val dispatcherFirst = Props.empty.withDispatcherFromConfig("pool").withDispatcherDefault
 
   "A Props" must {
 

akka-actor-typed-tests/src/test/scala/akka/actor/typed/scaladsl/DispatcherSelectorSpec.scala

@@ -0,0 +1,109 @@
+/*
+ * Copyright (C) 2019 Lightbend Inc. <https://www.lightbend.com>
+ */
+
+package akka.actor.typed.scaladsl
+
+import akka.actor.BootstrapSetup
+import akka.actor.setup.ActorSystemSetup
+import akka.actor.testkit.typed.scaladsl.ActorTestKit
+import akka.actor.testkit.typed.scaladsl.ScalaTestWithActorTestKit
+import akka.actor.testkit.typed.scaladsl.TestProbe
+import akka.actor.typed.ActorRef
+import akka.actor.typed.ActorSystem
+import akka.actor.typed.Behavior
+import akka.actor.typed.Props
+import akka.actor.typed.SpawnProtocol
+import com.typesafe.config.ConfigFactory
+import org.scalatest.WordSpecLike
+
+object DispatcherSelectorSpec {
+  val config = ConfigFactory.parseString("""
+      ping-pong-dispatcher {
+        executor = thread-pool-executor
+        type = PinnedDispatcher
+      }
+    """)
+
+  object PingPong {
+    case class Ping(replyTo: ActorRef[Pong])
+    case class Pong(threadName: String)
+
+    def apply(): Behavior[Ping] =
+      Behaviors.receiveMessage[Ping] { message =>
+        message.replyTo ! Pong(Thread.currentThread().getName)
+        Behaviors.same
+      }
+
+  }
+
+}
+
+class DispatcherSelectorSpec extends ScalaTestWithActorTestKit(DispatcherSelectorSpec.config) with WordSpecLike {
+  import DispatcherSelectorSpec.PingPong
+  import DispatcherSelectorSpec.PingPong._
+
+  "DispatcherSelector" must {
+
+    "select dispatcher from config" in {
+      val probe = createTestProbe[Pong]()
+      val pingPong = spawn(PingPong(), Props.empty.withDispatcherFromConfig("ping-pong-dispatcher"))
+      pingPong ! Ping(probe.ref)
+
+      val response = probe.receiveMessage()
+      response.threadName should startWith("DispatcherSelectorSpec-ping-pong-dispatcher")
+    }
+
+    "select same dispatcher as parent" in {
+      val parent = spawn(SpawnProtocol.behavior, Props.empty.withDispatcherFromConfig("ping-pong-dispatcher"))
+      val childProbe = createTestProbe[ActorRef[Ping]]()
+      parent ! SpawnProtocol.Spawn(PingPong(), "child", Props.empty.withDispatcherSameAsParent, childProbe.ref)
+
+      val probe = createTestProbe[Pong]()
+      val child = childProbe.receiveMessage()
+      child ! Ping(probe.ref)
+
+      val response = probe.receiveMessage()
+      response.threadName should startWith("DispatcherSelectorSpec-ping-pong-dispatcher")
+    }
+
+    "select same dispatcher as parent, several levels" in {
+      val grandParent = spawn(SpawnProtocol.behavior, Props.empty.withDispatcherFromConfig("ping-pong-dispatcher"))
+      val parentProbe = createTestProbe[ActorRef[SpawnProtocol.Spawn[Ping]]]()
+      grandParent ! SpawnProtocol.Spawn(
+        SpawnProtocol.behavior,
+        "parent",
+        Props.empty.withDispatcherSameAsParent,
+        parentProbe.ref)
+
+      val childProbe = createTestProbe[ActorRef[Ping]]()
+      grandParent ! SpawnProtocol.Spawn(PingPong(), "child", Props.empty.withDispatcherSameAsParent, childProbe.ref)
+
+      val probe = createTestProbe[Pong]()
+      val child = childProbe.receiveMessage()
+      child ! Ping(probe.ref)
+
+      val response = probe.receiveMessage()
+      response.threadName should startWith("DispatcherSelectorSpec-ping-pong-dispatcher")
+    }
+
+    "use default dispatcher if selecting parent dispatcher for user guardian" in {
+      val sys = ActorSystem(
+        PingPong(),
+        "DispatcherSelectorSpec2",
+        ActorSystemSetup.create(BootstrapSetup()),
+        Props.empty.withDispatcherSameAsParent)
+      try {
+        val probe = TestProbe[Pong]()(sys)
+        sys ! Ping(probe.ref)
+
+        val response = probe.receiveMessage()
+        response.threadName should startWith("DispatcherSelectorSpec2-akka.actor.default-dispatcher")
+      } finally {
+        ActorTestKit.shutdown(sys)
+      }
+    }
+
+  }
+
+}

akka-actor-typed-tests/src/test/scala/docs/akka/typed/DispatchersDocSpec.scala

@@ -47,6 +47,7 @@ object DispatchersDocSpec {
     context.spawn(yourBehavior, "ExplicitDefaultDispatcher", DispatcherSelector.default())
     context.spawn(yourBehavior, "BlockingDispatcher", DispatcherSelector.blocking())
     context.spawn(yourBehavior, "DispatcherFromConfig", DispatcherSelector.fromConfig("your-dispatcher"))
+    context.spawn(yourBehavior, "ParentDispatcher", DispatcherSelector.sameAsParent())
     //#spawn-dispatcher
 
     Behaviors.same

akka-actor-typed/src/main/scala/akka/actor/typed/Props.scala

@@ -10,6 +10,8 @@ import akka.annotation.InternalApi
 import scala.annotation.tailrec
 import scala.reflect.ClassTag
 
+import akka.actor.typed.internal.PropsImpl._
+
 object Props {
 
   /**
@@ -68,6 +70,11 @@ abstract class Props private[akka] () extends Product with Serializable {
    */
   def withDispatcherFromConfig(path: String): Props = DispatcherFromConfig(path, this)
 
+  /**
+   * Prepend a selection of the same executor as the parent actor to this Props.
+   */
+  def withDispatcherSameAsParent: Props = DispatcherSameAsParent(this)
+
   /**
    * Find the first occurrence of a configuration node of the given type, falling
    * back to the provided default if none is found.
@@ -125,21 +132,11 @@ abstract class Props private[akka] () extends Product with Serializable {
   }
 }
 
-/**
- * The empty configuration node, used as a terminator for the internally linked
- * list of each Props.
- */
-@InternalApi
-private[akka] case object EmptyProps extends Props {
-  override def next = throw new NoSuchElementException("EmptyProps has no next")
-  override def withNext(next: Props): Props = next
-}
-
 /**
  * Not for user extension.
  */
 @DoNotInherit
-sealed abstract class DispatcherSelector extends Props
+abstract class DispatcherSelector extends Props
 
 /**
  * Factories for [[DispatcherSelector]]s which describe which thread pool shall be used to run
@@ -155,7 +152,7 @@ object DispatcherSelector {
    * Scala API:
    * Run the actor on the default [[ActorSystem]] executor.
    */
-  def default(): DispatcherSelector = DispatcherDefault()
+  def default(): DispatcherSelector = DispatcherDefault.empty
 
   /**
    * Java API:
@@ -175,38 +172,10 @@ object DispatcherSelector {
    * ActorSystem terminates.
    */
   def fromConfig(path: String): DispatcherSelector = DispatcherFromConfig(path)
-}
-
-/**
- * INTERNAL API
- *
- * Use the [[ActorSystem]] default executor to run the actor.
- */
-@DoNotInherit
-@InternalApi
-private[akka] sealed case class DispatcherDefault(next: Props) extends DispatcherSelector {
-  @InternalApi
-  override def withNext(next: Props): Props = copy(next = next)
-}
-object DispatcherDefault {
-  // this is hidden in order to avoid having people match on this object
-  private val empty = DispatcherDefault(EmptyProps)
 
   /**
-   * Retrieve an instance for this configuration node with empty `next` reference.
+   * Run the actor on the same executor as the parent actor.
+   * @return
    */
-  def apply(): DispatcherDefault = empty
-}
-
-/**
- * Look up an executor definition in the [[ActorSystem]] configuration.
- * ExecutorServices created in this fashion will be shut down when the
- * ActorSystem terminates.
- *
- * INTERNAL API
- */
-@InternalApi
-private[akka] final case class DispatcherFromConfig(path: String, next: Props = Props.empty)
-    extends DispatcherSelector {
-  override def withNext(next: Props): Props = copy(next = next)
+  def sameAsParent(): DispatcherSelector = DispatcherSameAsParent.empty
 }

akka-actor-typed/src/main/scala/akka/actor/typed/internal/PropsImpl.scala

@@ -0,0 +1,43 @@
+/*
+ * Copyright (C) 2019 Lightbend Inc. <https://www.lightbend.com>
+ */
+
+package akka.actor.typed.internal
+
+import akka.actor.typed.DispatcherSelector
+import akka.actor.typed.Props
+import akka.annotation.InternalApi
+
+/**
+ * INTERNAL API
+ */
+@InternalApi private[akka] object PropsImpl {
+
+  /**
+   * The empty configuration node, used as a terminator for the internally linked
+   * list of each Props.
+   */
+  case object EmptyProps extends Props {
+    override def next = throw new NoSuchElementException("EmptyProps has no next")
+    override def withNext(next: Props): Props = next
+  }
+
+  final case class DispatcherDefault(next: Props) extends DispatcherSelector {
+    override def withNext(next: Props): Props = copy(next = next)
+  }
+  object DispatcherDefault {
+    val empty = DispatcherDefault(EmptyProps)
+  }
+
+  final case class DispatcherFromConfig(path: String, next: Props = Props.empty) extends DispatcherSelector {
+    override def withNext(next: Props): Props = copy(next = next)
+  }
+
+  final case class DispatcherSameAsParent(next: Props) extends DispatcherSelector {
+    override def withNext(next: Props): Props = copy(next = next)
+  }
+  object DispatcherSameAsParent {
+    val empty = DispatcherSameAsParent(EmptyProps)
+  }
+
+}

akka-actor-typed/src/main/scala/akka/actor/typed/internal/adapter/ActorRefFactoryAdapter.scala

@@ -3,9 +3,10 @@
  */
 
 package akka.actor.typed.internal.adapter
+
+import akka.ConfigurationException
 import akka.actor.typed._
 import akka.annotation.InternalApi
-import akka.ConfigurationException
 import akka.util.ErrorMessages
 
 /**

akka-actor-typed/src/main/scala/akka/actor/typed/internal/adapter/ActorSystemAdapter.scala

@@ -2,27 +2,39 @@
  * Copyright (C) 2016-2019 Lightbend Inc. <https://www.lightbend.com>
  */
 
-package akka.actor.typed
-package internal
-package adapter
+package akka.actor.typed.internal.adapter
 
 import java.util.concurrent.CompletionStage
 
-import akka.actor
+import scala.compat.java8.FutureConverters
+import scala.concurrent.ExecutionContextExecutor
+import scala.concurrent.Future
+
 import akka.Done
+import akka.actor
+import akka.actor.ActorRefProvider
 import akka.actor.ExtendedActorSystem
 import akka.actor.InvalidMessageException
-import akka.{ actor => untyped }
-
-import scala.concurrent.ExecutionContextExecutor
-import akka.util.Timeout
-
-import scala.concurrent.Future
+import akka.actor.typed.ActorRef
+import akka.actor.typed.ActorSystem
+import akka.actor.typed.Behavior
+import akka.actor.typed.DispatcherSelector
+import akka.actor.typed.Dispatchers
+import akka.actor.typed.Logger
+import akka.actor.typed.Props
+import akka.actor.typed.Scheduler
+import akka.actor.typed.Settings
+import akka.actor.typed.internal.ActorRefImpl
+import akka.actor.typed.internal.ExtensionsImpl
+import akka.actor.typed.internal.InternalRecipientRef
+import akka.actor.typed.internal.PropsImpl.DispatcherDefault
+import akka.actor.typed.internal.PropsImpl.DispatcherFromConfig
+import akka.actor.typed.internal.PropsImpl.DispatcherSameAsParent
+import akka.actor.typed.internal.SystemMessage
 import akka.annotation.InternalApi
-
-import scala.compat.java8.FutureConverters
-import akka.actor.ActorRefProvider
 import akka.event.LoggingFilterWithMarker
+import akka.util.Timeout
+import akka.{ actor => untyped }
 
 /**
  * INTERNAL API. Lightweight wrapper for presenting an untyped ActorSystem to a Behavior (via the context).
@@ -34,8 +46,8 @@ import akka.event.LoggingFilterWithMarker
 @InternalApi private[akka] class ActorSystemAdapter[-T](val untypedSystem: untyped.ActorSystemImpl)
     extends ActorSystem[T]
     with ActorRef[T]
-    with internal.ActorRefImpl[T]
-    with internal.InternalRecipientRef[T]
+    with ActorRefImpl[T]
+    with InternalRecipientRef[T]
     with ExtensionsImpl {
 
   // note that the untypedSystem may not be initialized yet here, and that is fine because
@@ -52,7 +64,7 @@ import akka.event.LoggingFilterWithMarker
   // impl ActorRefImpl
   override def isLocal: Boolean = true
   // impl ActorRefImpl
-  override def sendSystem(signal: internal.SystemMessage): Unit = sendSystemMessage(untypedSystem.guardian, signal)
+  override def sendSystem(signal: SystemMessage): Unit = sendSystemMessage(untypedSystem.guardian, signal)
 
   // impl InternalRecipientRef
   override def provider: ActorRefProvider = untypedSystem.provider
@@ -71,6 +83,7 @@ import akka.event.LoggingFilterWithMarker
       selector match {
         case DispatcherDefault(_)         => untypedSystem.dispatcher
         case DispatcherFromConfig(str, _) => untypedSystem.dispatchers.lookup(str)
+        case DispatcherSameAsParent(_)    => untypedSystem.dispatcher
       }
     override def shutdown(): Unit = () // there was no shutdown in untyped Akka
   }

akka-actor-typed/src/main/scala/akka/actor/typed/internal/adapter/PropsAdapter.scala

@@ -2,11 +2,13 @@
  * Copyright (C) 2017-2019 Lightbend Inc. <https://www.lightbend.com>
  */
 
-package akka.actor.typed
-package internal
-package adapter
+package akka.actor.typed.internal.adapter
 
 import akka.actor.Deploy
+import akka.actor.typed.Behavior
+import akka.actor.typed.DispatcherSelector
+import akka.actor.typed.Props
+import akka.actor.typed.internal.PropsImpl._
 import akka.annotation.InternalApi
 
 /**
@@ -19,9 +21,10 @@ import akka.annotation.InternalApi
       rethrowTypedFailure: Boolean = true): akka.actor.Props = {
     val props = akka.actor.Props(new ActorAdapter(behavior(), rethrowTypedFailure))
 
-    (deploy.firstOrElse[DispatcherSelector](DispatcherDefault()) match {
+    (deploy.firstOrElse[DispatcherSelector](DispatcherDefault.empty) match {
       case _: DispatcherDefault          => props
       case DispatcherFromConfig(name, _) => props.withDispatcher(name)
+      case _: DispatcherSameAsParent     => props.withDispatcher(Deploy.DispatcherSameAsParent)
     }).withDeploy(Deploy.local) // disallow remote deployment for typed actors
   }
 

akka-actor-typed/src/main/scala/akka/actor/typed/javadsl/Adapter.scala

@@ -7,7 +7,6 @@ package akka.actor.typed.javadsl
 import akka.actor
 import akka.actor.typed.Behavior
 import akka.actor.typed.Props
-import akka.actor.typed.EmptyProps
 import akka.actor.typed.ActorRef
 import akka.actor.typed.scaladsl.adapter._
 import akka.actor.typed.ActorSystem
@@ -36,7 +35,7 @@ object Adapter {
    *  `Behaviors.supervise`.
    */
   def spawnAnonymous[T](sys: akka.actor.ActorSystem, behavior: Behavior[T]): ActorRef[T] =
-    spawnAnonymous(sys, behavior, EmptyProps)
+    spawnAnonymous(sys, behavior, Props.empty)
 
   /**
    *  Spawn the given behavior as a child of the user actor in an untyped ActorSystem.
@@ -52,7 +51,7 @@ object Adapter {
    *  `Behaviors.supervise`.
    */
   def spawn[T](sys: akka.actor.ActorSystem, behavior: Behavior[T], name: String): ActorRef[T] =
-    spawn(sys, behavior, name, EmptyProps)
+    spawn(sys, behavior, name, Props.empty)
 
   /**
    *  Spawn the given behavior as a child of the user actor in an untyped ActorSystem.
@@ -68,7 +67,7 @@ object Adapter {
    *  `Behaviors.supervise`.
    */
   def spawnAnonymous[T](ctx: akka.actor.ActorContext, behavior: Behavior[T]): ActorRef[T] =
-    spawnAnonymous(ctx, behavior, EmptyProps)
+    spawnAnonymous(ctx, behavior, Props.empty)
 
   /**
    *  Spawn the given behavior as a child of the user actor in an untyped ActorContext.
@@ -84,7 +83,7 @@ object Adapter {
    *  `Behaviors.supervise`.
    */
   def spawn[T](ctx: akka.actor.ActorContext, behavior: Behavior[T], name: String): ActorRef[T] =
-    spawn(ctx, behavior, name, EmptyProps)
+    spawn(ctx, behavior, name, Props.empty)
 
   /**
    *  Spawn the given behavior as a child of the user actor in an untyped ActorContext.
@@ -155,5 +154,5 @@ object Adapter {
    * example of that.
    */
   def props[T](behavior: Creator[Behavior[T]]): akka.actor.Props =
-    props(behavior, EmptyProps)
+    props(behavior, Props.empty)
 }

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

@@ -10,15 +10,16 @@ import akka.routing._
 import akka.event._
 import akka.util.Helpers
 import akka.util.Collections.EmptyImmutableSeq
-
 import scala.util.control.NonFatal
 import java.util.concurrent.atomic.AtomicLong
 
 import scala.concurrent.{ ExecutionContextExecutor, Future, Promise }
 import scala.annotation.implicitNotFound
+
 import akka.ConfigurationException
 import akka.annotation.DoNotInherit
 import akka.annotation.InternalApi
+import akka.dispatch.Dispatchers
 import akka.serialization.Serialization
 import akka.util.OptionVal
 
@@ -513,8 +514,12 @@ private[akka] class LocalActorRefProvider private[akka] (
     // make user provided guardians not run on internal dispatcher
     val dispatcher =
       system.guardianProps match {
-        case None        => internalDispatcher
-        case Some(props) => system.dispatchers.lookup(props.dispatcher)
+        case None => internalDispatcher
+        case Some(props) =>
+          val dispatcherId =
+            if (props.deploy.dispatcher == Deploy.DispatcherSameAsParent) Dispatchers.DefaultDispatcherId
+            else props.dispatcher
+          system.dispatchers.lookup(dispatcherId)
       }
     val ref = new LocalActorRef(
       system,
@@ -621,17 +626,29 @@ private[akka] class LocalActorRefProvider private[akka] (
           }
         }
 
+        def parentDispatcher: String = supervisor match {
+          case withCell: ActorRefWithCell => withCell.underlying.props.dispatcher
+          case _                          => Deploy.NoDispatcherGiven
+        }
+
         val props2 =
           // mailbox and dispatcher defined in deploy should override props
           (if (lookupDeploy) deployer.lookup(path) else deploy) match {
             case Some(d) =>
               (d.dispatcher, d.mailbox) match {
-                case (Deploy.NoDispatcherGiven, Deploy.NoMailboxGiven) => props
-                case (dsp, Deploy.NoMailboxGiven)                      => props.withDispatcher(dsp)
-                case (Deploy.NoMailboxGiven, mbx)                      => props.withMailbox(mbx)
-                case (dsp, mbx)                                        => props.withDispatcher(dsp).withMailbox(mbx)
+                case (Deploy.NoDispatcherGiven, Deploy.NoMailboxGiven)      => props
+                case (Deploy.DispatcherSameAsParent, Deploy.NoMailboxGiven) => props.withDispatcher(parentDispatcher)
+                case (dsp, Deploy.NoMailboxGiven)                           => props.withDispatcher(dsp)
+                case (Deploy.NoDispatcherGiven, mbx)                        => props.withMailbox(mbx)
+                case (Deploy.DispatcherSameAsParent, mbx)                   => props.withDispatcher(parentDispatcher).withMailbox(mbx)
+                case (dsp, mbx)                                             => props.withDispatcher(dsp).withMailbox(mbx)
               }
-            case _ => props // no deployment config found
+            case _ =>
+              // no deployment config found
+              if (props.deploy.dispatcher == Deploy.DispatcherSameAsParent)
+                props.withDispatcher(parentDispatcher)
+              else
+                props
           }
 
         if (!system.dispatchers.hasDispatcher(props2.dispatcher))

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

@@ -10,13 +10,19 @@ import akka.routing._
 import akka.util.WildcardIndex
 import com.github.ghik.silencer.silent
 import com.typesafe.config._
-
 import scala.annotation.tailrec
 
+import akka.annotation.InternalApi
+
 object Deploy {
   final val NoDispatcherGiven = ""
   final val NoMailboxGiven = ""
   val local = Deploy(scope = LocalScope)
+
+  /**
+   * INTERNAL API
+   */
+  @InternalApi private[akka] final val DispatcherSameAsParent = ".."
 }
 
 /**

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

@@ -171,7 +171,7 @@ private[akka] class Mailboxes(
 
     if (deploy.mailbox != Deploy.NoMailboxGiven) {
       verifyRequirements(lookup(deploy.mailbox))
-    } else if (deploy.dispatcher != Deploy.NoDispatcherGiven && hasMailboxType) {
+    } else if (deploy.dispatcher != Deploy.NoDispatcherGiven && deploy.dispatcher != Deploy.DispatcherSameAsParent && hasMailboxType) {
       verifyRequirements(lookup(dispatcherConfig.getString("id")))
     } else if (hasRequiredType(actorClass)) {
       try verifyRequirements(lookupByQueueType(getRequiredType(actorClass)))

akka-docs/src/main/paradox/typed/dispatchers.md

@@ -2,7 +2,7 @@
 
 ## Dependency
 
-Dispatchers are part of core akka, which means that they are part of the akka-actor-typed dependency:
+Dispatchers are part of core Akka, which means that they are part of the akka-actor-typed dependency:
 
 @@dependency[sbt,Maven,Gradle] {
   group="com.typesafe.akka"
@@ -30,8 +30,11 @@ Scala
 Java
 :  @@snip [DispatcherDocTest.java](/akka-actor-typed-tests/src/test/java/jdocs/akka/typed/DispatchersDocTest.java) { #spawn-dispatcher }
 
-`DispatcherSelector` has two convenience methods to look up the default dispatcher and a dispatcher you can use to 
-execute actors that block e.g. a legacy database API that does not support @scala[`Future`]@java[`CompletionStage`]s.
+`DispatcherSelector` has a few convenience methods:
+
+* @scala[`DispatcherSelector.default`]@java[`DispatcherSelector.defaultDispatcher`] to look up the default dispatcher
+* `DispatcherSelector.blocking` can be used to execute actors that block e.g. a legacy database API that does not support @scala[`Future`]@java[`CompletionStage`]s
+* `DispatcherSelector.sameAsParent` to use the same dispatcher as the parent actor
 
 The final example shows how to load a custom dispatcher from configuration and replies on this being in your application.conf: