Akka/Scala example source code file (migration-guide-2.3.x-2.4.x.rst)

This example Akka source code file (migration-guide-2.3.x-2.4.x.rst) is included in my "Source Code Warehouse" project. The intent of this project is to help you more easily find Akka and Scala source code examples by using tags.

All credit for the original source code belongs to akka.io; I'm just trying to make examples easier to find. (For my Scala work, see my Scala examples and tutorials.)

Akka tags/keywords

actorclassification, actorsystem, akka, assertionerror, eventstream, if, java, javalogger, scala, the

The migration-guide-2.3.x-2.4.x.rst Akka example source code

.. _migration-2.4:

################################
 Migration Guide 2.3.x to 2.4.x
################################

The 2.4 release contains some structural changes that require some
simple, mechanical source-level changes in client code.

When migrating from earlier versions you should first follow the instructions for
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>`.

TestKit.remaining throws AssertionError
=======================================

In earlier versions of Akka `TestKit.remaining` returned the default timeout configurable under
"akka.test.single-expect-default". This was a bit confusing and thus it has been changed to throw an
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
=======================================================================

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
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``.

If you have implemented a custom event bus, you will need to pass in the actor system through the constructor now:

.. includecode:: ../scala/code/docs/event/EventBusDocSpec.scala#actor-bus

If you have been creating EventStreams manually, you now have to provide an actor system and *start the unsubscriber*:

.. includecode:: ../../../akka-actor-tests/src/test/scala/akka/event/EventStreamSpec.scala#event-bus-start-unsubscriber-scala

Please note that this change affects you only if you have implemented your own busses, Akka's own ``context.eventStream``
is still there and does not require any attention from you concerning this change.

Removed Deprecated Features
===========================

The following, previously deprecated, features have been removed:

* akka-dataflow

* akka-transactor

* durable mailboxes (akka-mailboxes-common, akka-file-mailbox)

* Cluster.publishCurrentClusterState

* akka.cluster.auto-down, replaced by akka.cluster.auto-down-unreachable-after in Akka 2.3

* Old routers and configuration.

  Note that in router configuration you must now specify if it is a ``pool`` or a ``group``
  in the way that was introduced in Akka 2.3.

* Timeout constructor without unit
 
* JavaLoggingEventHandler, replaced by JavaLogger

* UntypedActorFactory

* Java API TestKit.dilated, moved to JavaTestKit.dilated