!clt #13523 Don't expose sender in cluster client replies

akka-cluster-tools/src/main/scala/akka/cluster/client/ClusterClient.scala

@@ -524,7 +524,7 @@ object ClusterReceptionist {
       def receive = {
         case Ping           ⇒ // keep alive from client
         case ReceiveTimeout ⇒ context stop self
-        case msg            ⇒ client forward msg
+        case msg            ⇒ client.tell(msg, Actor.noSender)
       }
     }
   }
@@ -546,10 +546,11 @@ object ClusterReceptionist {
  *
  * Response messages from the destination actor are tunneled via the receptionist
  * to avoid inbound connections from other cluster nodes to the client, i.e.
- * the `sender`, as seen by the destination actor, is not the client itself.
+ * the `sender()`, as seen by the destination actor, is not the client itself.
- * The `sender` of the response messages, as seen by the client, is preserved
+ * The `sender()` of the response messages, as seen by the client, is `deadLetters`
- * as the original sender, so the client can choose to send subsequent messages
+ * since the client should normally send subsequent messages via the `ClusterClient`.
- * directly to the actor in the cluster.
+ * It is possible to pass the the original sender inside the reply messages if
+ * the client is supposed to communicate directly to the actor in the cluster.
  *
  */
 final class ClusterReceptionist(pubSubMediator: ActorRef, settings: ClusterReceptionistSettings)

akka-cluster-tools/src/multi-jvm/scala/akka/cluster/client/ClusterClientSpec.scala

@@ -41,11 +41,13 @@ object ClusterClientSpec extends MultiNodeConfig {
 
   testTransport(on = true)
 
+  case class Reply(msg: Any, node: Address)
+
   class TestService(testActor: ActorRef) extends Actor {
     def receive = {
       case msg ⇒
         testActor forward msg
-        sender() ! msg + "-ack"
+        sender() ! Reply(msg + "-ack", Cluster(context.system).selfAddress)
     }
   }
 
@@ -116,7 +118,7 @@ class ClusterClientSpec extends MultiNodeSpec(ClusterClientSpec) with STMultiNod
         val c = system.actorOf(ClusterClient.props(
           ClusterClientSettings(system).withInitialContacts(initialContacts)), "client1")
         c ! ClusterClient.Send("/user/testService", "hello", localAffinity = true)
-        expectMsg("hello-ack")
+        expectMsgType[Reply].msg should be("hello-ack")
         system.stop(c)
       }
       runOn(fourth) {
@@ -190,18 +192,18 @@ class ClusterClientSpec extends MultiNodeSpec(ClusterClientSpec) with STMultiNod
           ClusterClientSettings(system).withInitialContacts(initialContacts)), "client2")
 
         c ! ClusterClient.Send("/user/service2", "bonjour", localAffinity = true)
-        expectMsg("bonjour-ack")
+        val reply = expectMsgType[Reply]
-        val lastSenderAddress = lastSender.path.address
+        reply.msg should be("bonjour-ack")
-        val receptionistRoleName = roleName(lastSenderAddress) match {
+        val receptionistRoleName = roleName(reply.node) match {
           case Some(r) ⇒ r
-          case None    ⇒ fail("unexpected missing roleName: " + lastSender.path.address)
+          case None    ⇒ fail("unexpected missing roleName: " + reply.node)
         }
         testConductor.exit(receptionistRoleName, 0).await
         remainingServerRoleNames -= receptionistRoleName
         within(remaining - 3.seconds) {
           awaitAssert {
             c ! ClusterClient.Send("/user/service2", "hi again", localAffinity = true)
-            expectMsg(1 second, "hi again-ack")
+            expectMsgType[Reply](1 second).msg should be("hi again-ack")
           }
         }
         system.stop(c)
@@ -220,11 +222,11 @@ class ClusterClientSpec extends MultiNodeSpec(ClusterClientSpec) with STMultiNod
           ClusterClientSettings(system).withInitialContacts(initialContacts)), "client3")
 
         c ! ClusterClient.Send("/user/service2", "bonjour2", localAffinity = true)
-        expectMsg("bonjour2-ack")
+        val reply = expectMsgType[Reply]
-        val lastSenderAddress = lastSender.path.address
+        reply.msg should be("bonjour2-ack")
-        val receptionistRoleName = roleName(lastSenderAddress) match {
+        val receptionistRoleName = roleName(reply.node) match {
           case Some(r) ⇒ r
-          case None    ⇒ fail("unexpected missing roleName: " + lastSender.path.address)
+          case None    ⇒ fail("unexpected missing roleName: " + reply.node)
         }
         // shutdown all but the one that the client is connected to
         remainingServerRoleNames.foreach { r ⇒
@@ -244,9 +246,9 @@ class ClusterClientSpec extends MultiNodeSpec(ClusterClientSpec) with STMultiNod
         val expectedAddress = node(receptionistRoleName).address
         awaitAssert {
           c ! ClusterClient.Send("/user/service2", "bonjour3", localAffinity = true)
-          expectMsg(1 second, "bonjour3-ack")
+          val reply = expectMsgType[Reply](1 second)
-          val lastSenderAddress = lastSender.path.address
+          reply.msg should be("bonjour3-ack")
-          lastSenderAddress should be(expectedAddress)
+          reply.node should be(expectedAddress)
         }
         system.stop(c)
       }

akka-docs/rst/java/cluster-client.rst

@@ -54,9 +54,10 @@ to the named topic.
 Response messages from the destination actor are tunneled via the receptionist
 to avoid inbound connections from other cluster nodes to the client, i.e.
 the ``sender()``, as seen by the destination actor, is not the client itself.
-The ``sender()`` of the response messages, as seen by the client, is preserved
+The ``sender()`` of the response messages, as seen by the client, is ``deadLetters``
-as the original sender(), so the client can choose to send subsequent messages
+since the client should normally send subsequent messages via the ``ClusterClient``.
-directly to the actor in the cluster.
+It is possible to pass the the original sender inside the reply messages if
+the client is supposed to communicate directly to the actor in the cluster.
 
 While establishing a connection to a receptionist the ``ClusterClient`` will buffer
 messages and send them when the connection is established. If the buffer is full

akka-docs/rst/project/migration-guide-2.3.x-2.4.x.rst

@@ -297,6 +297,17 @@ is now started as a ``system`` actor instead of a ``user`` actor, i.e. the defau
 the ``ClusterClient`` initial contacts has changed to
 ``"akka.tcp://system@hostname:port/system/receptionist"``.  
 
+ClusterClient sender
+====================
+
+In 2.3 the ``sender()`` of the response messages, as seen by the client, was the 
+actor in cluster.
+
+In 2.4 the ``sender()`` of the response messages, as seen by the client, is ``deadLetters``
+since the client should normally send subsequent messages via the ``ClusterClient``.
+It is possible to pass the the original sender inside the reply messages if
+the client is supposed to communicate directly to the actor in the cluster.
+
 Akka Persistence
 ================
 

akka-docs/rst/scala/cluster-client.rst

@@ -54,9 +54,10 @@ to the named topic.
 Response messages from the destination actor are tunneled via the receptionist
 to avoid inbound connections from other cluster nodes to the client, i.e.
 the ``sender()``, as seen by the destination actor, is not the client itself.
-The ``sender()`` of the response messages, as seen by the client, is preserved
+The ``sender()`` of the response messages, as seen by the client, is ``deadLetters``
-as the original sender(), so the client can choose to send subsequent messages
+since the client should normally send subsequent messages via the ``ClusterClient``.
-directly to the actor in the cluster.
+It is possible to pass the the original sender inside the reply messages if
+the client is supposed to communicate directly to the actor in the cluster.
 
 While establishing a connection to a receptionist the ``ClusterClient`` will buffer
 messages and send them when the connection is established. If the buffer is full