Basics of Akka

Basics of

Akka

Akka is a toolkit to build *concurrent, *distributed, *fault torerant apps.

Akka is a toolkit to build *concurrent, *distributed, *fault torerant apps.

並行計算したり分散処理したり耐障害性があるような

concurrent -> Actorsdistributed -> Remotingfault torerant -> Supervision

concurrent -> Actorsdistributed -> Remotingfault torerant -> Supervision

アクター

リモートアクター

監視

Actors

Merchant

Warrior

Actors States

Messages

Each actor runsconcurrently

Actors communiate through messages

Each actor has state

Actors are scalable

Too much load!

I scaaale out!

Remoting

Server1

It’s O.K.

Server1

Out of cap

Server2Server1

Remoting

Ditribute across servers

Supervision

Supervisor

Children

exceptionexception

restart!restart!

Some code

import akka.actor._import akka.util.Timeoutimport akka.pattern.askimport concurrent.duration._import concurrent.Futureimport concurrent.ExecutionContext.Implicits.global

case class Pay(amount: Int)

case class Apple()

class Merchant extends Actor {  var gold: Int = 0  def receive = {    case Pay(amount) if amount >= 50 =>      gold += 50      sender ! Apple()  }}

val system = ActorSystem()val merchant: ActorRef = system.actorOf(Props(new Merchant))

val future: Future[Apple] = (merchant ? Pay(50)).mapTo[Apple]

// Callbacks

future.onSuccess { case apple: Apple =>    // Eat it}

future.onFailure { case failure =>    println("onFailure called with: " + failure)}

// Wait for the reply

import concurrent.Await

val result: Apple = Await.result(future, atMost = 10 seconds)

// for-comprehensions

for { apple <- future foo <- anotherFuture} yield doSomething(apple, foo)

See:

SIP-14 - Futures and Promises

http://docs.scala-lang.org/sips/pending/futures-promises.html

Scalingout?

val merchant: ActorRef = system.actorOf(Props(new Merchant))

val router: ActorRef = system.actorOf( Props[Merchant] .withRouter( SmallestMailboxRouter( nrOfInstances = 10 ) ), name = "merchantRouter" )

val future: Future[Apple] = (merchant ? Pay(50)).mapTo[Apple]

val future: Future[Apple] = (router ? Pay(50)).mapTo[Apple]

Excercise

“Hi!”

“Hi!”

“Hi!”

class EchoActor extends Actor {  def receive = {    case <1> =>      sender ! <2>  }}

“Hi!”

“Hi!”

class EchoActor extends Actor {  def receive = {    case msg =>      sender ! msg  }}

“Hi!”

“Hi!”

Further topics

Akka is composed of many tools:

actor, testkit, remote, cluster, transactor, agent, zeromq, camel, ...

Just use what you need

See:

http://akka.io/docs/

Read it now!

http://www.manning.com/roestenburg/

Thank you!