The key insight is that an actor is a tiny VM and you just need to make the VM state durable.
- not all states transitions need to be durable. If performance matters you’ll have to get your actors to call something like a « saveState » from time to time, otherwise every single property change is going to have an overhead in terms of performance.
- what does « durable » mean ? Surely, just having the state of an actor saved in the memory of the supervisor isn’t enough. If the two are on the same server and the server shuts down, it’s game over. You need a « persistence » service / actor, but that thing is going to have to persist the state of all the actors in your system. I don’t see how that can work if you’ve got millions of actors running in parallel.
I've never heard of an actor system able to automatically respawn actors with their previous state (the whole system would look like a tree of cached data, each layer responsible for saving the leafs under it, with a huge "persist to DB" on top , wouldn't it ?). Does erlang OTP do those kind of things ?
Edit: also, are you Prof "Carl" Hewitt ? The one that invented actors ? I'd be honored you found a question of mine about actors excellent...