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Akka

Akka. Quick Intro for hAkkers. What is it?. Toolkit for development of scalable distributed fault-tolerant applications in Scala or Java. Modules Offered. actors (typed / untyped / testkit) very slick Futures / Promises STM async-http camel spring cluster (upcoming in 2.0)

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Akka

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  1. Akka Quick Intro for hAkkers

  2. What is it? Toolkit for development of • scalable • distributed • fault-tolerant applications in Scala or Java Roland Kuhn @ Scalathon

  3. Modules Offered • actors (typed / untyped / testkit) • very slick Futures / Promises • STM • async-http • camel • spring • cluster (upcoming in 2.0) • … (to be filled, possibly by you!) Roland Kuhn @ Scalathon

  4. Project Details • site at http://akka.io • source at https://github.com/jboner/akka • https://www.assembla.com/spaces/akka for tickets (need to “watch” the space) • Apache License 2.0 • Contributor’s License Agreement needed for submissions Roland Kuhn @ Scalathon

  5. Hacking Guide • Performance is King! • memory footprint • minimize allocations • avoid blocking operations • Every feature or fix needs a corresponding test case • Always update docs together with code • reStructured Text within git repo Roland Kuhn @ Scalathon

  6. Goals for Scalathon • Hack demo application • get feedback on API & docs • get feedback on testkit • contribute to improve experience for newcomers Roland Kuhn @ Scalathon

  7. Getting Started • Strong encapsulation of Actor • only access through ActorRef • only constructible inside factory method • no calling of Actor methods from the outside, except through mailbox • Communication via Channel[T] • allows sending • may be passed around Roland Kuhn @ Scalathon

  8. import akka.actor._ class A extendsActor { defreceive = { case“ping” => self reply“pong” } } class B(a: ActorRef) extendsActor { var last: UntypedChannel = NullChannel defreceive = { case“ping” => last = self.channel a !“ping” case“pong” => last safe_!“pong” } } import org.scalatest.WordSpec import org.scalatest.matchers.MustMatchers import akka.testkit.TestKit import akka.util.duration._ class ABSpec extends WordSpec with MustMatchers withTestKit { “Some B” must { “return answer obtained from A” in { val a = actorOf[A].start() val b = actorOf(new B(a)).start() within(500 millis) { b !“ping” expectMsg(“pong”) } } } } Actor Sample Roland Kuhn @ Scalathon

  9. Future Sample import akka.dispatch.Future import Future.flow val x = Future(calculateSomeExpensiveInt()) val y = Future(calculateSomeExpensiveFloat()) val z = flow { val f = someActor ?x() // someActor will reply at some point with a Float Some(f() / y()) } recover { case _: ArithmeticException => None } z onResult { case Some(x) => doSomething(x) case None => log.error(“calculation failed”) } val result = z.await.result// if you must really block Roland Kuhn @ Scalathon

  10. Conclusion • Forget what you knew about “composing” concurrent programs • View actors as fundamental building blocks encapsulating state • Go wild! Roland Kuhn @ Scalathon

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