When are threads created for Scala actor's reacts?

Question

After reading about using react in actors in Scala, I thought react\'s would share the same thread given there weren\'t multiple react\'s

Answer 1

It is true that for a pure event-based actor, its reacting code runs on the same thread as message sending code.

But in Scala, since it's not desirable to block a thread when an actor calls a blocking operation inside its react code and to unify event-based and thread-based actors(being able to compose them), both type of actors uses the same thread pool but the thread-based actors get their own threads whereas event-based actors shares threads based on a task queue. For details, please see Actors that Unify Threads and Events by Philipp Haller and Martin Odersky