How to pass data to `OnActivateAsync()` to initialize my stateful actor?

Question

I am creating a reliable, stateful, service actor.

Question:

Is there a way to pass initialization data during the actor proxy creation (ActorProxy.Create())? Basically an equivalent to a constructor for my actor.

Current thoughts:

I can achieve this by following up the proxy creation call with an actor method call in charge of initializing the state.

E.g.

//Danger, the following calls are not atomic
ITokenManager tokenActor = ActorProxy.Create<IMyActor>(actorId, "AppName");
//Something could happen here and leave my actor in an unknown state
await tokenActor.InitializeAsync(desiredInitialState);

My concern with such approach:

• This operation is not atomic. It may leave my actor in an inconsistent state
• This initialization method is now available throughout the life of the actor, which is undesired.

Answer 1

A couple thoughts for you here. For one, is the data that you need to do initialization really not available to the actor itself during OnActivateAsync? Normally if I rely on getting some initial data into my actor's state this is how I would do it.

protected override Task OnActivateAsync()
{
   if (State == null)
   {
       var initialState = await externalSource.GetSomeState();
       // simplified here but map the values properly onto the actual actor state
       this.State = initialState;
       return base.OnActivateAsync();
   }
}

The other thought is that if you truly can't have the actor retrieve the data during it's own activation it's very easy for you to create a boolean property that is part of the actor state indicating whether or the other activation you're talking about has ever occurred.

 public Task InitializeAsync(State someState)
 {
     if (State.IsActivated)
     {
         // log out here that someone is attempting to reactivate when they shouldn't
         return Task.CompletedTask;
     }

     State = someState;
     State.IsActivated = true;
     return Task.CompletedTask;
 }

This way while technically the method will be available to be called for the lifetime of the actor, you have a single threaded guarantee that it will only actually do something the very first time it is called.

Answer 2

It seems like the best approach to have an atomic initialization is keep the initialization data in some external store, and during OnActivateAsync() consume this data from that store.