Actor Based Concurrency

Whistle-stop tour of Akka - slides for the #micromanchester microservices conference.

Transcript

1. Actor Based Concurrency Amy O’ Leary Autotrader amyblarney@gmail.com amyblarney@gmail.com Amy O’ Leary 1
2. amyblarney@gmail.com Amy O’ Leary 2
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4. The Actor Model amyblarney@gmail.com Amy O’ Leary 4
5. Actors vs Microsystems Microsystems • Stand-alone components that serve a single purpose • May be in themselves multithreaded Actors • Isolated, single-threaded components that encapsulate both state and behavior • Can be used to implement microservice environments Amy O’ Leary amyblarney@gmail.com 5
6. In concurrent systems, managing state is hard Managing mutable state leads to: • Race conditions • Visibility issues • Lack of atomicity amyblarney@gmail.com Amy O’ Leary 6
7. In an actor system, all internal state is maintained by actors • State held by an actor can be thought to be immutable and atomic • In Akka, only one message within an actor is processed at a time, enforcing atomicity amyblarney@gmail.com Amy O’ Leary 7
8. Written in by And now also available on Available on amyblarney@gmail.com Amy O’ Leary 8
9. Adding Akka to your application public class HelloActor extends UntypedActor { public void onReceive(Object message) { if (message instanceof HelloMessage) { System.out.println( "My message is: " + ( (HelloMessage)message ).getMessage() ); } } } amyblarney@gmail.com Amy O’ Leary 9
10. Starting your application with Akka ActorSystem actorSystem = ActorSystem.create( "MySystem" ); ActorRef actorRef = actorSystem.actorOf( new Props( HelloActor.class ), "myActor" ); actorRef.tell( new HelloMessage( "Hello, Akka!" ) ); amyblarney@gmail.com Amy O’ Leary 10
11. Adding routing to your Akka application akka.actor.deployment { /parent/router1 { router = round-robin-pool nr-of-instances = 5 } } amyblarney@gmail.com Amy O’ Leary 11
12. Adding routing to your Akka application ActorRef router1 = getContext() .actorOf(FromConfig.getInstance() .props(Props.create(HelloActor.class)), "router1"); amyblarney@gmail.com Amy O’ Leary 12
13. Fault tolerance Ever tried. Ever failed. No matter. Try Again. Fail again. Fail better. Samuel Beckett amyblarney@gmail.com Amy O’ Leary 13
14. Building a distributed system • More scalable • Easier to release small components separately • Single tenancy – easier to trace a fault to a single component • Easier to change resources in a bottleneck component amyblarney@gmail.com Amy O’ Leary 14
15. MVP -> 1 JVM amyblarney@gmail.com Amy O’ Leary 15
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17. Akka Remoting • Start with a single JVM with components designed as actors • Scale up by using Akka Remoting • Any number of actors can occupy their own server • Easy to configure – no code changes needed! • Can combine remoting with routing. amyblarney@gmail.com Amy O’ Leary 17
18. Akka Remoting Add the maven dependency <dependency> <groupId>com.typesafe.akka</groupId> <artifactId>akka-remote_2.11</artifactId> <version>2.4-SNAPSHOT</version> </dependency> amyblarney@gmail.com Amy O’ Leary 18
19. Akka Remoting Add to your application.conffile: akka { actor { provider = "akka.remote.RemoteActorRefProvider" } remote { enabled-transports = ["akka.remote.netty.tcp"] netty.tcp{ hostname = "127.0.0.1" port = 2552 } } } amyblarney@gmail.com Amy O’ Leary 19
20. Akka Remoting Configure your application to be able to talk to your remote actors akka { actor { deployment { /sampleActor { remote = "akka.tcp://sampleActorSystem@127.0.0.1:2553" } } } } amyblarney@gmail.com Amy O’ Leary 20
21. Akka Remoting Use routing to set up a remote actor in several locations akka.actor.deployment { /parent/remotePool { router = round-robin-pool nr-of-instances = 10 target.nodes= ["akka.tcp://app@10.0.0.2:2552", "akka://app@10.0.0.3:2552"] } } amyblarney@gmail.com Amy O’ Leary 21
22. A warning note • Increasing concurrency can increase complexity • Error reporting can be vague – no stack trace • Debugging from one actor to another is cumbersome • Still need to learn about concurrency in Java! amyblarney@gmail.com Amy O’ Leary 22
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24. What did we learn? • The actor model can be used to manage state in a concurrent system • Akka is a great framework for easily implementing an actor based system • Akka can be easily scaled up to a distributed system amyblarney@gmail.com Amy O’ Leary 24