Akka introtalk HyScala DEC 2016
2 likes•256 views
The document introduces Akka, a framework for building concurrent and distributed applications in Scala using the actor model. It explains the benefits of the actor model over traditional thread-based programming, outlining key concepts and providing code examples for setting up and managing actors in an Akka application. Additionally, it touches on communication between actors and the importance of asynchronous message passing.
![Messages
case class Item(name: String, quantity: Int,
rate: Double)
case object Done
case class Order(item: List[Item])](https://image.slidesharecdn.com/akkaintrotalk-hyscala-161209102457/85/Akka-introtalk-HyScala-DEC-2016-17-320.jpg)
![Cart Actor
class CartActor extends Actor {
val items = ListBuffer[Item]()
def receive: Receive = {
case item: Item => items.+=(item)
// done with adding items to cart
case Done => ???
}
}](https://image.slidesharecdn.com/akkaintrotalk-hyscala-161209102457/85/Akka-introtalk-HyScala-DEC-2016-18-320.jpg)
![all together ....
ouput:
Here your bill Bill(175.0)
object AkkaIntroTalk extends App {
val actorSystem = ActorSystem("actorsystem")
val billingActor = actorSystem.actorOf(Props[BillingActor],
val cartActor = actorSystem.actorOf(Props(classOf[CartAct
cartActor ! Item("Apple", 3, 20.0)
cartActor ! Item("Orange", 3, 15.0)
cartActor ! Item("Butter", 1, 70.0)
cartActor ! Done
}](https://image.slidesharecdn.com/akkaintrotalk-hyscala-161209102457/85/Akka-introtalk-HyScala-DEC-2016-21-320.jpg)
Akka introtalk HyScala DEC 2016
- 1. Introduction to Akka (for Scala infants !!!!) ------- Prasanna Kumar
- 2. Excuse me !!!!! I assume that you ,,,, already stepped in to "Scala"land and its a JVM language written some Scala code and understand its fundementals familiar with SBT (like maven)
- 3. About this talk is for "Impatient" help you to write Akka Code "right now" in Scala distinguish Actor model and Akka not teaching the partial functions and algebraic data types in Scala cover all aspects of Akka
- 4. Agenda What makes us to consider Actor Model Understanding Actor model of programming Introducing to Akka Akka Actor model approach Setting up Writing Actors using Akka (with code examples) Moving forward (touchbase) Q&A
- 5. What makes us to consider Actor Model Modern day programming need to process lot of data in terms of - volume - variety - velocity our code started to use multiple CPU cores within the machine or across a cluster
- 6. What makes us to consider Actor Model (contd) Obvious option is to consider aysnc programming with "threads" (atleast in Java) programming for threads is a cumbersome requires a lot of boiler-plate code communicaiton between threads (with in and outside JVM) is tedious
- 7. What makes us to consider Actor Model (contd) does this means the thread model is broken ?? No .. but it serves as a good foundation just that it need better async abstraction
- 8. So how do we solve this ? for writing concurrent and distributed programs, we need threads to communicate easily "Actor Model" to the rescue
- 9. What is an Actor this model prescribes an "Actor" backed by a thread model (by the underlying runtime or OS) Async abstraction can be expressed as an actor in the form of Class or function an Actor framework can create & manage actor clients can communicate only by passing messages (Async'ly) to the actor actors can also communicate between themselves
- 10. What is an Actor unlike Thread, an Actor message driven responds to certain messages from other Actors (or non-actors) can handle only one message at any instant of time
- 11. Actor model of programming (contd)
- 12. Introducing Akka Scala/Java API whcih implements the Actor model provides a framework to create & manage actors , backed by JVM Thread model Akka provides a mailbox for each actor : in- memory queue to stage messages clients acan send messages either by ! send or ? ask pattern (more on that later) actor reveives messages and respond to clients Akka actors use pattern matching to hande messages
- 14. Setting up sbt co-ordinates in build.sbt name := "hyscala-akka-intro-talk" version := "1.0" scalaVersion := "2.11.8" libraryDependencies ++= Seq( "com.typesafe.akka" %% "akka-actor" % "2.4.14") open the project in your IDE to get started
- 15. plain simple actor class PlainActor extends Actor { def receive: Receive = { case _ => } } actor which can respond to some messages: class PrimitiveHandlingActor extends Actor { def receive: Receive = { case "hello world" => println("""received hello world """) case 11 => println("received ") case _ => println("some other data type") } }
- 16. simple shopping cart cart and order as two actors show case their interaction with simple messages covers actor to actor message passing
- 17. Messages case class Item(name: String, quantity: Int, rate: Double) case object Done case class Order(item: List[Item])
- 18. Cart Actor class CartActor extends Actor { val items = ListBuffer[Item]() def receive: Receive = { case item: Item => items.+=(item) // done with adding items to cart case Done => ??? } }
- 19. Cart Actor - next version class CartActor(billingActor: ActorRef) extends Actor { ... case Done => billingActor ! Order(items.toList) items.clear() }
- 20. Billing Actor class BilingActor extends Actor { def receive: Receive = { case order: Order => println(s"Here your bill ${Bill(order.items.foldLeft(0.0)((a } }
- 21. all together .... ouput: Here your bill Bill(175.0) object AkkaIntroTalk extends App { val actorSystem = ActorSystem("actorsystem") val billingActor = actorSystem.actorOf(Props[BillingActor], val cartActor = actorSystem.actorOf(Props(classOf[CartAct cartActor ! Item("Apple", 3, 20.0) cartActor ! Item("Orange", 3, 15.0) cartActor ! Item("Butter", 1, 70.0) cartActor ! Done }
- 22. Learning Akka Online Akka Docs Let it crash - blog Books Learning Akka Reactive Programming with Scala and Akka - (I've authored this book)
- 23. Moving forward (touchbase) Actor heirarchy FSM Load Balacing Akka Clustering Akka HTTP
- 24. Takeaway https://github.com/prassee/hyscala-akka-intro- talk/tree/master
- 25. Q&A