Any reason for deprecating shutdown method?

Question

When shuting down an ActorSystem I found that ActorSystem::shutdown was deprecated. It's suggested "Use the terminate() method instead".

But the decumentation of those methods is almost the same:

  /**
   * Terminates this actor system. This will stop the guardian actor, which in turn
   * will recursively stop all its child actors, then the system guardian
   * (below which the logging actors reside) and the execute all registered
   * termination handlers (see [[ActorSystem#registerOnTermination]]).
   * Be careful to not schedule any operations on completion of the returned future
   * using the `dispatcher` of this actor system as it will have been shut down before the
   * future completes.
   */
  def terminate(): Future[Terminated]

and

  /**
   * Stop this actor system. This will stop the guardian actor, which in turn
   * will recursively stop all its child actors, then the system guardian
   * (below which the logging actors reside) and the execute all registered
   * termination handlers (see [[ActorSystem#registerOnTermination]]).
   */
  @deprecated("Use the terminate() method instead", "2.4")
  def shutdown(): Unit

with one exception that the return type has changed. What was the reason of deprecating shutdown? Was it not safe?

Answer 1

It appears that the deprecation was to follow the "terminate" convention used in other areas of the project, as well as exposing termination events.

The important part is the termination events:

The termination hooks allow system actors to perform final cleanup before the system shuts down or restarts - in this particular case it's to let remote systems know that any remote-deployed actors on the shutting down system are dead, but there are other cases where this gets used inside Akka core

See the following for more information:

• The related Akka issue
• The related Akka.NET issue
• The Actor system shutdown section of their 2.3 to 2.4 migration guide