Akka with Java

Introduction to Akka on Java platform.
Code samples:
https://bitbucket.org/pklimkowski/akka-presentation-samples

Transcript

1. Akka with Java Piotr Klimkowski
2. What is Akka “Akka is an open-source toolkit and runtime simplifying the construction of concurrent and distributed applications on the JVM. Akka supports multiple programming models for concurrency, but it emphasizes actor-based concurrency, with inspiration drawn from Erlang.” (Wikipedia) • Initial release: 2009 • Production users: ebay, cisco, bbc, amazon …
3. Actors you say ?
4. What is an Actor • Smallest unit when building an application • Receives and sends messages to other actors • Message is any Object - have to be immutable • Actor processes one message at a time • Form a hierarchical structure (supervision) • Could be viewed a Person
5. Sample 1: Hello World
6. Message delivery guarantees • at-most-once-delivery • “Delivery is guaranteed if nothing breakes” (Erlang) • guaranteed delivery possible with explicit ACK- RETRY protocol, ReliableProxy pattern • Akka Persistence - (experimental in 2.3.x) UntypedPersistentActorWithAtLeastOnceDelivery
7. More on Actors • State • Behaviour • Children • and a supervision strategy to handle their faults • Mailbox - FIFO (default), priority, bounded • Termination - dead letter mailbox
8. Actor lifecycle • preStart() - called right after starting actor, allows for one time initialisation • postStop() - after actor is stopped, resources cleanup • preRestart() - right before restart, by default sends termination request to children and calls postStop() • postRestart() - by default calls preStart()
9. Sample 2: Supervision strategy
10. Lifecycle monitoring • DeathWatch - transition from alive to dead • ActorContext.watch() / unwatch() • Actor may monitor any other actor • Useful when depending on some other actors (not necessarily children actors)
11. Sample 3: Death Watch
12. Futures • Avoid blocking as much as possible • ExecutionContext • Patterns.ask() / Patterns.pipe() • Callbacks - OnSuccess, OnFailure, OnComplete • Monadic methods - map(), flatMap() …
13. Sample 4: Futures
14. Remoting • Scale out • Look up / create actors on remote systems • Remote death watch • Props and messages must be serialisable • Routers with remote destinations • Security
15. Sample 5: Remoting
16. Testing • akka-testkit • synchronous unit testing • TestActorRef • asynchronous integration testing • JavaTestKit
17. Sample 6: Testing
18. Not this time • Configuration (Typesafe Config) • Routing • Clustering • Persistence • Finite State Machines • Apache Camel integration • Custom serializers
19. That’s it. Thanks