How to supervise actors in Akka and handle exceptions

Question

I am trying to improve the error handling with the actors in my system. Sometimes, when processing data, something goes wrong, and I need to stop and restart the actor, as well as log some information regarding this failure.

I have a Supervisor, which has 5 actors working for it. So I need to be able to supervise all of them. I found this link:

https://doc.akka.io/docs/akka/current/typed/fault-tolerance.html

regarding this, but I don't think it is very clear on where to implement the code:

Behaviors.supervise(behavior).onFailure[IllegalStateException](SupervisorStrategy.restart)

Where exactly is this code supposed to go?

Thanks

It's not totally clear whether you're asking about the classic or the typed API (if it's the typed API I'd suggest adding the `akka-typed` tag (perhaps replacing the `actor` tag). Supervision in the classic API (e.g. you have code that `extends Actor`) is very different and documented at https://doc.akka.io/docs/akka/current/supervision-classic.html — Levi Ramsey, Oct 04 '21 at 16:15
Hi, yes sorry you are right. I am using Classic Actors. I am trying to find something that seems applicable to my scenario. Each supervisor has 5 child actors, and if one of these actors fail, I need to log it at error level, and retrieve the data that this actor was processing. @LeviRamsey — TreyBCollier, Oct 05 '21 at 09:49

score 1 · Answer 1 · answered Oct 04 '21 at 11:33

You can think of this supervisor as another behavioiur which wraps your behaviour inside of it.

Lets say you want to have following HelloWorld actor.

object HelloWorldActor {

  sealed trait Command
  case class HelloCommand(name: String) extends Command

  def apply(): Behavior[Command] =
    Behaviors.receiveMessage[Command] { 
      case msg: HelloCommand =>
        println(s"Hello ${msg.name}")
        Behaviors.same
    }

}

Now, you can "wrap" this "behaviour" with a "supervisor"

object SupervisedHelloWorldActor {

  sealed trait Command
  case class HelloCommand(name: String) extends Command

  def apply(): Behavior[Command] =
    Behaviors.supervise(
      Behaviors.receiveMessage[Command] { 
        case HelloCommand(name) =>
          println(s"Hello ${name}")
          Behaviors.same
      }
    ).onFailure(onFailure[IllegalStateException](SupervisorStrategy.restart))

}

How to supervise actors in Akka and handle exceptions

1 Answers1