Akka 2.0 Reloaded
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Akka 2.0 is a toolkit for building highly concurrent, distributed, and fault-tolerant applications on the JVM. It provides actors as the core abstraction for concurrency and distribution. Actors encapsulate state and behavior and communicate asynchronously by message passing. Akka provides elasticity so that new messages can be processed while an actor is busy. It also includes features for fault tolerance using a "let it crash" model and transparent distribution through routing.
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Akka 2.0 Reloaded
- 1. 2.0 Reloaded Meetu Maltiar Email: meetu@knoldus.com Twitter:@meetumaltiar
- 2. Akka 2.0 Akka name comes from Sami mythology is actually name of a goddess of wisdom and beauty. Akka incidentally means sister in Telugu!!
- 3. The Problem It is way too hard to build => correct highly concurrent systems => truly scalable systems => self-healing, fault-tolerant systems
- 4. What is Akka? Right abstraction with actors for concurrent, fault-tolerant and scalable applications For Fault-Tolerance uses “let it crash” model Abstraction for transparent distribution for load
- 5. Introducing Actors Actor is an entity encapsulating behavior, state and a mailbox to receive messages For a message received by Actor a thread is allocated to it Then Actors behavior is applied to the message and potentially some state is changed or messages is passed to other Actors
- 6. Introducing Actors.. There is elasticity between message processing and addition of new messages. New messages can be added while actor execution is happening. When processing of messages is completed thread is deallocated from the actor. It can be reallocated a thread at a later time
- 11. Create Application import akka.actor.ActorSystem val system = ActorSystem("firstApp")
- 12. My First Actor import akka.actor.{ Actor, Props } class MyFirstActor extends Actor { def receive = { case msg => println("Hello!!") } }
- 13. Create Actors import akka.actor.{ ActorSystem, Props } val system = ActorSystem("firstApp") val myFirstActor = system.actorOf(Props[MyFirstActor]) MyFirstActor is an ActorRef Create a top level actor
- 14. Stop Actors system stop myFirstActor Also stops all actors in hierarchy
- 15. Send: ! myFirstActor ! “Hello” fire-forget
- 16. Ask: ? import akka.pattern.ask implicit val timeout = Timeout(50000 milliseconds) val future = myActor ? "hello" Await.result(future, timeout.duration).asInstanceOf[Int] Returns a Future[Any]
- 17. Reply import akka.actor.Actor class LongWorkingActor extends Actor { def receive = { case number: Int => sender ! (“Hi I received ” + number) } }
- 20. Let It Crash Fault Tolerance
- 27. Actor Path val actorRef = system.actorFor("akka://actorPathApp/user/pa rent/child") val parent = context.actorFor("..") val sibling = context.actorFor("../sibling") val refPath = actorRef.path
- 28. Supervision class Supervisor extends Actor { override val supervisorStrategy = OneForOneStrategy(maxNrOfRetries = 10, withinTimeRange = 1 minute) { case _: ArithmeticException => Resume case _: NullPointerException => Restart case _: IllegalArgumentException => Stop case _: Exception => Escalate } }
- 29. Manage Failure class FaultTolerantService extends Actor { def receive = { case msg => println(msg) } override def preRestart(reason: Throwable, message: Option[Any]) = { // clean up before restart } override def postRestart(reason: Throwable) = { // init after restart } }
- 31. References Viktor Klang talk on Akka 2.0 at NE Scala symposium Akka website akka.io