Added functionality for a router client to retrieve the current routees of that router. See #1495

akka-actor-tests/src/test/scala/akka/routing/RoutingSpec.scala

@@ -59,6 +59,34 @@ class RoutingSpec extends AkkaSpec with DefaultTimeout with ImplicitSender {
       expectMsg(Terminated(router))
     }
 
+    "be able to send their routees" in {
+      val doneLatch = new CountDownLatch(1)
+
+      class TheActor extends Actor {
+        val routee1 = context.actorOf(Props[TestActor], "routee1")
+        val routee2 = context.actorOf(Props[TestActor], "routee2")
+        val routee3 = context.actorOf(Props[TestActor], "routee3")
+        val router = context.actorOf(Props[TestActor].withRouter(ScatterGatherFirstCompletedRouter(routees = List(routee1, routee2, routee3))))
+
+        // Stop one of the routees - which should exclude it from the router's list of active routees
+        routee3 ! PoisonPill
+
+        def receive = {
+          case RouterRoutees(iterable) ⇒
+            iterable.exists(_ == "routee1") must be(true)
+            iterable.exists(_ == "routee2") must be(true)
+            iterable.exists(_ == "routee3") must be(false)
+            doneLatch.countDown()
+          case "doIt" ⇒
+            router ! CurrentRoutees
+        }
+      }
+
+      val theActor = system.actorOf(Props(new TheActor), "theActor")
+      theActor ! "doIt"
+      doneLatch.await(1, TimeUnit.SECONDS) must be(true)
+    }
+
   }
 
   "no router" must {

akka-actor/src/main/scala/akka/routing/Routing.scala

@@ -4,12 +4,8 @@
 package akka.routing
 
 import akka.actor._
-import akka.japi.Creator
-import java.lang.reflect.InvocationTargetException
-import akka.config.ConfigurationException
 import java.util.concurrent.atomic.AtomicInteger
-import akka.util.{ ReflectiveAccess, Timeout }
-import akka.AkkaException
+import akka.util.Timeout
 import scala.collection.JavaConversions._
 import java.util.concurrent.TimeUnit
 
@@ -33,6 +29,9 @@ private[akka] class RoutedActorRef(_system: ActorSystemImpl, _props: Props, _sup
   def applyRoute(sender: ActorRef, message: Any): Iterable[Destination] = message match {
     case _: AutoReceivedMessage ⇒ Nil
     case Terminated(_)          ⇒ Nil
+    case CurrentRoutees ⇒
+      sender ! RouterRoutees(_routees map (_.path.name))
+      Nil
     case _ ⇒
       if (route.isDefinedAt(sender, message)) route(sender, message)
       else Nil
@@ -148,6 +147,17 @@ trait Router extends Actor {
  */
 case class Broadcast(message: Any)
 
+/**
+ * Sending this message to a router will make it send back its currently used routees.
+ * The routees will be sent as a RouterRoutees message to the "requester".
+ */
+case object CurrentRoutees
+
+/**
+ * Message used to carry information about what routees the router is currently using.
+ */
+case class RouterRoutees(routees: Iterable[String])
+
 /**
  * For every message sent to a router, its route determines a set of destinations,
  * where for each recipient a different sender may be specified; typically the