The document discusses how the Akka framework implements the actor model for concurrent and distributed programming in Scala. It describes how actors avoid shared mutable state by communicating asynchronously through message passing. Akka provides features like remote actors, dynamic hot-swapping of actor behavior, supervisors that restart failed child actors, and software transactional memory for shared immutable data structures.

1. “Simpler Scalability, Fault-Tolerance, Concurrency & Remoting through Actors”

3. Event-driven actors

4. Remote actors

5. Supervision

8. Obviously, we can do just fine with shared mutable state and locks

9. But abstraction is good

11. Communication by asynchronous message passing

12. Concurrency without shared mutable state and locks

13. Made popular by Erlang

15. Actors can encapsulate mutable state, but should communicate with immutable messages

16. class Greeter extends Actor {

17. def act() {

18. while (true) {

19. receive {

20. case name: String => println("Hello, "+name)

21. case _ => println("That's not a name!")

22. }

23. }

24. }

25. }

27. class Greeter extends Actor {

28. def receive = {

29. case name: String => println("Hello, "+name)

30. case _ => println("That's not a name!")

31. }

32. }

35. Communication with remote actors is transparent

36. class RemoteGreeter extends Greeter {

37. self.makeRemote("192.1.33.7", 1337)

38. }

40. Enables fault tolerance

41. “Let it crash”, aka “Embrace failure” – discourages defensive programming; simpler programs result

42. Supervision: Restart Strategies One for one All for one

45. Optimistic: log, don't lock

46. Akka provides several STM managed data structures, e.g.

47. val names = TransactionalVector [ String ]()

48. val ages = TransactionalMap [ String , Int ]()

49. These provide Atomicity, Consistency and Isolation

50. Akka's persistence modules provide Durability: Cassandra, Redis, MongoDB,

52. class Bank extends Transactor {

53. def receive = {

54. case Transfer (from, to, amount) =>

55. to ! Deposit (amount)

56. from ! Withdraw (amount)

57. }

58. }

60. Thanks! Twitter: bmjames