concurrency - Thread.sleep inside Scala actors

Question

Is it correct to use Thread.sleep(5000); inside an actor? Does it actualy make an actor sleep for 5 seconds? Is there a simple alternative to make an actor sleep for some seconds?

Answer 1

Anything that blocks a thread is not advised within Akka. If the Actor is configured with a a shared thread pool (default behavior) then using Thread.sleep will withhold a thread from that pool that could be doing work for other Actors.

If one really must block, then an actor may be configured to have its own thread. This can be done by configuring a custom dispatcher for the actor to use, the full details are here.

The recognized alternative to blocking is to schedule a callback to the actor via a timer, for example send a message after 5 seconds..

akkaSystem.scheduler.scheduleOnce(5 seconds, actor, "msgFoo")

The Akka scheduler is documented here: http://doc.akka.io/docs/akka/2.3.6/scala/scheduler.html