Hello, Akka community!
Sometimes there are situations when you don't have an ActorRef instance but
you know where to ask for it. It may be because actor is still haven't
being created and actor creation procedure requires some long-running tasks
to be completed for instance your application requires actor A that have a
dependency on component B which in turn depends on resource C that may not
be retrieved on application startup... or any other precondition where
actor could not exist...
But you have to give this ActorRef out of ActorSystem for example to Play!
controller or some different service (let's call it "client D"), whatever
but you don't want to show the implementation detail about actor still does
not exist, you just want to pass ActorRef as a constructor parameter. What
would you do?
In traditional systems I'd solve it with some kind of ProxyActorRef that'd
look something like that:
class ProxyActorRef(provider: () => Future[ActorRef]) extends ActorRef with
ScalaActorRef {
private val futureRef = provider()
override def path: ActorPath = ???
override def !(message: Any)(implicit sender: ActorRef): Unit =
futureRef.onComplete({
case Success(ref) => ref.tell(message, sender)
case _ => // do nothing
})
}
but with current akka implementation I just can't do it because
of ProxyActorRef does not confirm to InternalActorRef and InternalActorRef
is private[akka]
Usually akka have a way to solve most of problems that could happen - *do
anyone knows how to solve this kind of problem?*
And to have separate actor in front of actor A is not a solution because
actor A can be Router.fromConfig and nesting all the calls to distinct
actor:
- makes all effort on building configurable proxy worthless
- can have a performance impact
<https://doc.akka.io/docs/akka/current/scala/routing.html#how-routing-is-designed-within-akka>
any way if performance could be sacrificed than simple router
<https://doc.akka.io/docs/akka/current/scala/routing.html#a-simple-router>
with routing logic at actor rather than at actorRef would be much better
solution, but what if that is not a case and performance is significant?
And also to have componentB/resourceC acquire logic separate at actor A
also couldn't be an answer because that way you couldn't expect componentB
as a constructor dependency so actor starts at a state when it just can't
do the work which it supooses to so your actor A should become a FSM and
this approach is rather overhead/overcomplicated.
And to wrap expectation for ActorRef into another object which is not
instanceof ActorRef (couldn't be used with akka.patterns._ for example) is
also not a solution because you don't want to show your implementation
detail about that dependency may not ready when "clientC" gets created.
Do anyone have any idea around it? Or may be pull request to akka with such
functionality can be a good thing?
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