The router "head" actor.
Implement the routing logic by returning a partial function of partial function from (sender, message) to a set of destinations.
RouteeProvider responsible for creating or
looking up routees.
Java API: get the singleton instance
Routers with dynamically resizable number of routees return the akka.routing.Resizer to use.
Dispatcher ID to use for running the “head” actor, i.
SupervisorStrategy for the created Router actor.
Check that everything is there which is needed.
Overridable merge strategy, by default completely prefers “this” (i.