A cluster is one logical actor hierarchy which spans multiple nodes, hence it does not make sense to support system.actorOf: instead Props need to be supplied when creating the system, to be instantiated as the system’s guardian as described in #2305. Since ActorSystem will still be used locally and must retain the capability of creating top-level local actors, introduce a new ClusterSystem which does not extend ActorRefFactory.

The remaining question becomes then what to do about context.system, which would still have to extend ActorRefFactory as otherwise actors could not be reused when going from “local” to “cluster”. Two possible solutions would be:

• throw an exception, necessitating the adaption of the actor to cluster rules
• send a message to the guardian to ask it to create the actor, which would make it possible to keep the actor working by supplying a suitable cluster guardian

Please comment.