How do I scale my Scala REST application that uses Akka?

Question

I have a Scala application using Akka that receives REST requests, makes some operations against a database, and responds with some information to the client. As it is, my db operations take a long time and my REST-enabled actor is unable to respond to new requests in the meantime, even though I could run lots of operations concurrently against the DB. I'm using the javax.ws.rs annotations to REST-enable methods in my actor.

The question; what is the best way to enable my application to handle a large number of concurrent requests?

EDIT: I'll add some sample code.

  import se.scalablesolutions.akka.actor._
  import javax.ws.rs._

  @Path("/test")
  class TestService {

    @GET
    def status() = 
      actorPool !! Status(session).
        getOrElse(<error>Unable to connect to service</error>)
  }

  class TestActor {

    def receive = {
      case Status() => {
        reply(SomeObject.slowDBMethod)
      }
    }
  }

  case class Status()

EDIT2: This is what I'm getting in the log. I'm sending the three requests from my browser as fast as I can switch tabs and press F5, but the RS bean still waits for the first request to complete before handling the next.

[INFO] [2010-08-29 16:27:03,232] [akka:event-driven:dispatcher:global-15] c.n.StatusActor: got Slow request
[INFO] [2010-08-29 16:27:06,916] [akka:event-driven:dispatcher:global-10] c.n.StatusActor: got Slow request
[INFO] [2010-08-29 16:27:10,589] [akka:event-driven:dispatcher:global-3] c.n.StatusActor: got Slow request

Answer 1

Once you get a request, you should create a new actor to handle that request. Pass on the original sender so the newly created actor knows who to answer to.

Answer 2

Hey Magnus,

you seem to be using an older version of Akka.

I recommend to upgrade to 0.10 (which separates Actors and the RS-Beans), then you can use LoadBalancer1 (and2) to throttle the workload, or take advantage of the WorkStealingDispatcher3 (and4)

Does that help?