= #17342 Make 2.4 binary compatible with 2.3

(cherry picked from commit 89af8bdb90)

* remove final identifier in serializers

i* revert/deprecate ProtobufSerializer.ARRAY_OF_BYTE_ARRAY

* adding back compatible empty constructor in serializers

* make FSM.State compatible

* add back ActorPath.ElementRegex

* revert SocketOption changes and add SocketOptionV2
  see a6d3704ef6

* problem filter for ActorSystem and ActorPath

* problem filter for ByteString

* problem filter for deprecated Timeout methods

* BalancingPool companion

* ask

* problem filter for ActorDSL

* event bus

* exclude hasSubscriptions

* exclude some problems in testkit

* boundAddress and addressFromSocketAddress

* Pool nrOfInstances

* PromiseActorRef

* check with 2.3.9

* migration guide note

* explicit exclude of final class problems

akka-docs/rst/java/code/docs/event/EventBusDocTest.java

@@ -39,7 +39,7 @@ import akka.event.japi.ScanningEventBus;
 //#scanning-bus
 
 //#actor-bus
-import akka.event.japi.ActorEventBus;
+import akka.event.japi.ManagedActorEventBus;
 
 //#actor-bus
 
@@ -232,7 +232,7 @@ public class EventBusDocTest {
   
   static
   //#actor-bus
-  public class ActorBusImpl extends ActorEventBus<Notification> {
+  public class ActorBusImpl extends ManagedActorEventBus<Notification> {
 
     // the ActorSystem will be used for book-keeping operations, such as subscribers terminating
     public ActorBusImpl(ActorSystem system) {
@@ -304,7 +304,7 @@ public class EventBusDocTest {
   }
   
   @Test
-  public void demonstrateActorClassification() {
+  public void demonstrateManagedActorClassification() {
       //#actor-bus-test
       ActorRef observer1 = new JavaTestKit(system).getRef();
       ActorRef observer2 = new JavaTestKit(system).getRef();

akka-docs/rst/java/event-bus.rst

@@ -115,7 +115,7 @@ type :class:`ActorRef`.
 
 This classification requires an :class:`ActorSystem` in order to perform book-keeping
 operations related to the subscribers being Actors, which can terminate without first
-unsubscribing from the EventBus. ActorClassification maitains a system Actor which
+unsubscribing from the EventBus. ManagedActorClassification maitains a system Actor which
 takes care of unsubscribing terminated actors automatically.
 
 The necessary methods to be implemented are illustrated with the following example:

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

@@ -11,6 +11,19 @@ When migrating from earlier versions you should first follow the instructions fo
 migrating :ref:`1.3.x to 2.0.x <migration-2.0>` and then :ref:`2.0.x to 2.1.x <migration-2.1>`
 and then :ref:`2.1.x to 2.2.x <migration-2.2>` and then :ref:`2.2.x to 2.3.x <migration-2.3>`.
 
+Binary Compatibility
+====================
+
+Akka 2.4.x is backwards binary compatible with previous 2.3.x versions apart from the following
+exceptions. This means that the new JARs are a drop-in replacement for the old one 
+(but not the other way around) as long as your build does not enable the inliner (Scala-only restriction).
+
+The following parts are not binary compatible with 2.3.x:
+
+* akka-testkit and akka-remote-testkit
+* experimental modules, such as akka-persistence and akka-contrib
+* features, classes, methods that were deprecated in 2.3.x and removed in 2.4.x 
+
 Advanced Notice: TypedActors will go away
 ========================================
 
@@ -31,13 +44,14 @@ In earlier versions of Akka `TestKit.remaining` returned the default timeout con
 AssertionError if called outside of within. The old behavior however can still be achieved by
 calling `TestKit.remainingOrDefault` instead.
 
-EventStream and ActorClassification EventBus now require an ActorSystem
-=======================================================================
+EventStream and ManagedActorClassification EventBus now require an ActorSystem
+==============================================================================
 
 Both the ``EventStream`` (:ref:`Scala <event-stream-scala>`, :ref:`Java <event-stream-java>`) and the
-``ActorClassification`` Event Bus (:ref:`Scala <actor-classification-scala>`, :ref:`Java <actor-classification-java>`) now
+``ManagedActorClassification``, ``ManagedActorEventBus`` (:ref:`Scala <actor-classification-scala>`, :ref:`Java <actor-classification-java>`) now
 require an ``ActorSystem`` to properly operate. The reason for that is moving away from stateful internal lifecycle checks
-to a fully reactive model for unsubscribing actors that have ``Terminated``.
+to a fully reactive model for unsubscribing actors that have ``Terminated``. Therefore the ``ActorClassification``
+and ``ActorEventBus`` was deprecated and replaced by ``ManagedActorClassification`` and ``ManagedActorEventBus`` 
 
 If you have implemented a custom event bus, you will need to pass in the actor system through the constructor now:
 
@@ -63,25 +77,6 @@ Which turns out to be useful in many systems where same-state transitions actual
 
 In case you do *not* want to trigger a state transition event when effectively performing an ``X->X`` transition, use ``stay()`` instead.
 
-More control over Channel properties in Akka-IO
-===============================================
-Method signatures for ``SocketOption`` have been changed to take a channel instead of a socket. The channel's socket
-can be retrieved by calling ``channel.socket``. This allows for accessing new NIO features in Java 7.
-
-========================================  =====================================
-                 2.3                                      2.4
-========================================  =====================================
-``beforeDatagramBind(DatagramSocket)``    ``beforeBind(DatagramChannel)``
-``beforeServerSocketBind(ServerSocket)``  ``beforeBind(ServerSocketChannel)``
-``beforeConnect(Socket)``                 ``beforeBind(SocketChannel)``
-\                                         ``afterConnect(DatagramChannel)``
-\                                         ``afterConnect(ServerSocketChannel)``
-``afterConnect(Socket)``                  ``afterConnect(SocketChannel)``
-========================================  =====================================
-
-A new class ``DatagramChannelCreator`` which extends ``SocketOption`` has been added. ``DatagramChannelCreator`` can be used for
-custom ``DatagramChannel`` creation logic. This allows for opening IPv6 multicast datagram channels.
-
 Cluster Sharding Entry Path Change
 ==================================
 Previously in ``2.3.x`` entries were direct children of the local ``ShardRegion``. In examples the ``persistenceId`` of entries

akka-docs/rst/scala/code/docs/event/EventBusDocSpec.scala

@@ -121,12 +121,12 @@ object EventBusDocSpec {
 
   //#actor-bus
   import akka.event.ActorEventBus
-  import akka.event.ActorClassification
+  import akka.event.ManagedActorClassification
   import akka.event.ActorClassifier
 
   final case class Notification(ref: ActorRef, id: Int)
 
-  class ActorBusImpl(val system: ActorSystem) extends ActorEventBus with ActorClassifier with ActorClassification {
+  class ActorBusImpl(val system: ActorSystem) extends ActorEventBus with ActorClassifier with ManagedActorClassification {
     type Event = Notification
 
     // is used for extracting the classifier from the incoming events
@@ -179,7 +179,7 @@ class EventBusDocSpec extends AkkaSpec {
     //#scanning-bus-test
   }
 
-  "demonstrate ActorClassification" in {
+  "demonstrate ManagedActorClassification" in {
     //#actor-bus-test
     val observer1 = TestProbe().ref
     val observer2 = TestProbe().ref

akka-docs/rst/scala/event-bus.rst

@@ -115,7 +115,7 @@ type :class:`ActorRef`.
 
 This classification requires an :class:`ActorSystem` in order to perform book-keeping
 operations related to the subscribers being Actors, which can terminate without first
-unsubscribing from the EventBus. ActorClassification maitains a system Actor which
+unsubscribing from the EventBus. ManagedActorClassification maitains a system Actor which
 takes care of unsubscribing terminated actors automatically.
 
 The necessary methods to be implemented are illustrated with the following example: