akka doesn't keep track of your actors ;) You can think of actor children as part of the state:
- You would need to store that child hierarchy somewhere (you don't need to use Akka.Persistence, maybe a simple db request would be enough)
- If you're using cluster sharding, config key
remember-entities=true will serve similar role (using Akka.Persistence).
- If you have a cluster, you could potentially use Akka.DistributedData and store child actors using something like
ORSet<>. This set will be replicated over other cluster nodes, so when your actor system will come back up, it just need to Get the value of the ORSet from the corresponding key and restore children based on that data.