![case class Greeting(who: String)
class GreetingActor extends Actor with ActorLogging {
override def receive: Receive = {
case Greeting(who) => println(s"Hello $who")
}
}
object Main extends App {
val system = ActorSystem("MySystem")
val greeter = system.actorOf(Props[GreetingActor], name = "greeter")
greeter ! Greeting("Scala")
}
Simple example](https://image.slidesharecdn.com/scalameetupreactivesystem-180403142435/85/Building-Reactive-System-with-Akka-25-320.jpg)
![Elasticity: Create multiple instance of Actor
● Define a router
val router: ActorRef =
context.actorOf(RoundRobinPool(5).props(Props[WorkerActor]), "router")
● Configuration file
akka.actor.deployment {
/parent/router1 {
router = round-robin-pool
nr-of-instances = 5
}
}](https://image.slidesharecdn.com/scalameetupreactivesystem-180403142435/85/Building-Reactive-System-with-Akka-29-320.jpg)
![Elastic: Create multiple instance of Actor
val router = {
val routees =
Vector.fill(NUMBER_OF_WORKER) {
val r =
context.actorOf(Props(classOf[ExecuteOp
erationRuleWorker], ioContextManager))
context watch r
ActorRefRoutee(r)
}
Router(AccountIdRoutingLogic(),
routees)
}
class AccountIdRoutingLogic extends
RoutingLogic {
val next = new AtomicLong
override def select(message: Any,
routees: immutable.IndexedSeq[Routee]):
Routee =
if (routees.nonEmpty) {
val size = routees.size
val operationRuleMessage =
message.asInstanceOf[ExecuteOperationRule
]
val index =
operationRuleMessage.account.identifier.v
alue
routees((index % size).toInt)
} else {
NoRoutee
}
}](https://image.slidesharecdn.com/scalameetupreactivesystem-180403142435/85/Building-Reactive-System-with-Akka-30-320.jpg)
![Elasticity: Actor Cluster
akka {
actor {
provider = cluster
}
cluster {
seed-nodes = ["akka.tcp://AkkaClusterDemo@127.0.0.1:2551"]
# roles = ["role"]
}
remote {
log-remote-lifecycle-events = off
netty.tcp {
hostname = ${args.host}
port = ${args.port}
}
}
}](https://image.slidesharecdn.com/scalameetupreactivesystem-180403142435/85/Building-Reactive-System-with-Akka-32-320.jpg)
Building Reactive System with Akka
- 1. Building Reactive System with Akka Nguyen Tung LamSepteni Technology Scala Hanoi Meetup 2018
- 2. Who am I? ● Facebook: https://www.facebook.com/lam.nguyentung ● Email: [email protected] ● UET - VNU ● Java/Scala developer
- 3. Agenda ● Reactive System: What/Why ? ● How to build the “Reactive System” ? ○ Akka Framework ○ Actor model ○ Demo
- 4. What is the “Reactive System” ?
- 5. What is the “Reactive System” ? ReactiveX
- 6. Reactive
- 7. Why we need the “Reactive System” ?
- 8. In the past ● Nodes: 10s ● Response time: x seconds ● Maintenance downtime: hours ● Data volume: Gbs
- 9. Today ● Nodes: 1000x ● Response time: milliseconds ● Maintenance downtimes: ○ zero ->100% up time ● Data volume: TBs -> PBs
- 10. What is Tumblr's technology stack?
- 12. Responsive ● The system responds in a timely manner if at all possible. ● Realtime user interface
- 13. ● Recover quickly from failures ○ Software ○ Hardware ○ Network ● Needed: ○ Loose coupling ○ Supervisor hierarchies Resilient
- 14. ● The system stays responsive under varying workload. ● The system can react to changes in the input rate by increasing or decreasing the resources allocated to service these inputs. Elastic
- 15. Message Driven ● The system rely on asynchronous message-passing to establish a boundary between components that ensures ○ loose coupling ○ Isolation ○ location transparency.
- 16. How to build the “Reactive System” ?
- 17. What is the Akka? https://akka.io/ - A framework and runtime engine for building reactive system on JVM - Implement the Actor model - Simple concurrent & Distributed systems - Resilient by design - Elastic & Decentralized - Higher performance - 50 million msg/sec on a single machine - 2.5 million actors per GB of heap - Written in Scala language, has Scala and Java binding
- 18. Why we need the Actor model ?
- 19. Object Oriented Programming ● Encapsulation: Internal data of an object is not accessible directly from the outside.
- 20. Object Oriented Programming (Next) ● Using lock to solve the problem ● But: ○ Lock seriously limit concurrency (Caller thread is blocked, it cannot do any other work) ○ Deadlock?
- 21. Actor Model ● Actor are asynchronous and non-blocking ○ Communicate only via message passing ○ Lock-free concurrency ○ Have a mailbox for inbound messages ○ Always process message in order
- 22. Actor Model
- 23. Actor Model ● Actor live in hierarchy ○ Actor can create other actors ○ Used for supervising: Fault tolerance ● Actor have a reference ○ Using actor ref (phone number)
- 24. How to create the Actor with Akka?
- 25. case class Greeting(who: String) class GreetingActor extends Actor with ActorLogging { override def receive: Receive = { case Greeting(who) => println(s"Hello $who") } } object Main extends App { val system = ActorSystem("MySystem") val greeter = system.actorOf(Props[GreetingActor], name = "greeter") greeter ! Greeting("Scala") } Simple example
- 26. Java vs Scala
- 27. Resilience: Dealing with failure ● Supervision ○ Restart ○ Resume ○ Stop ○ Escalate ● Supervisor strategies ○ One-for-one ○ All-for-one
- 28. Akka Supervision class WorkerActor extends Actor { override def receive: Receive = { case Greeting(who) => println(s"Hello $who") case Crash(exception) => crash(exception) } def crash(how: String): Unit = { how match { case "arithmetic" => throw new ArithmeticException case "null" => throw new NullPointerException case "illegal" => throw new IllegalArgumentException case _ => throw new Exception } } class MasterActor extends Actor { override def receive: Receive = { case Create(props, name) => context.actorOf(props, name) } override val supervisorStrategy: SupervisorStrategy = { AllForOneStrategy(maxNrOfRetries = 5, withinTimeRange = 10 seconds) { case _: ArithmeticException => Resume case _: NullPointerException => Restart case _: IllegalArgumentException => Stop case _: Exception => Escalate }
- 29. Elasticity: Create multiple instance of Actor ● Define a router val router: ActorRef = context.actorOf(RoundRobinPool(5).props(Props[WorkerActor]), "router") ● Configuration file akka.actor.deployment { /parent/router1 { router = round-robin-pool nr-of-instances = 5 } }
- 30. Elastic: Create multiple instance of Actor val router = { val routees = Vector.fill(NUMBER_OF_WORKER) { val r = context.actorOf(Props(classOf[ExecuteOp erationRuleWorker], ioContextManager)) context watch r ActorRefRoutee(r) } Router(AccountIdRoutingLogic(), routees) } class AccountIdRoutingLogic extends RoutingLogic { val next = new AtomicLong override def select(message: Any, routees: immutable.IndexedSeq[Routee]): Routee = if (routees.nonEmpty) { val size = routees.size val operationRuleMessage = message.asInstanceOf[ExecuteOperationRule ] val index = operationRuleMessage.account.identifier.v alue routees((index % size).toInt) } else { NoRoutee } }
- 32. Elasticity: Actor Cluster akka { actor { provider = cluster } cluster { seed-nodes = ["akka.tcp://[email protected]:2551"] # roles = ["role"] } remote { log-remote-lifecycle-events = off netty.tcp { hostname = ${args.host} port = ${args.port} } } }
- 33. Thanks you!
Editor's Notes
- #7: React JS Created in 2014 with +20k sign
- #11: https://www.quora.com/What-is-Tumblrs-technology-stack
- #13: Responsive systems focus on providing rapid and consistent response times, establishing reliable upper bounds so they deliver a consistent quality of service.
- #15: jamie madrox
- #23: https://letsdobigdata.files.wordpress.com/2016/03/actormodel-2.png