Building Reactive applications with Akka

2. Building Reactive applications using Akka Nilanjan Raychaudhuri @nraychaudhuri

3. Reactive Applications 3 @nraychaudhuri

4. Essence of Reactive applications

5. Reactive Traits

7. Akka is enabler of Reactive applications

8. • Individual entities that can only communicate by passing messages • Excellent for isolating mutable state and protecting it without locks • Location transparency for remote and clustered topologies • Supervision • Well-suited for creating state machines • Fault tolerance via Supervision Reactive Applications 8

9. Reference Architecture Web Tier (Play) Work Tier (Akka) responsive event driven Reactive Applications 9 Play Server Play Server Play Server Play Server Akka Master Router Akka Router Standby Akka Worker Akka Worker Akka Worker Akka Worker Akka Worker scalable resilient

10. Message-driven Reactive applications are architected based on loosely coupled design

11. Reactive Applications Message-Driven • Loosely coupled architecture, easier to extend, maintain, evolve • Asynchronous and non-blocking • Concurrent by design, immutable state • Lower latency and higher throughput 11 “Clearly, the goal is to do these operations concurrently and non-blocking, so that entire blocks of seats or sections are not locked. We’re able to find and allocate seats under load in less than 20ms without trying very hard to achieve it.” Andrew Headrick, Platform Architect, Ticketfly

12. Introducing Actor Model

13. 13 Actor model A computational model that embodies: ✓ Processing ✓ Storage ✓ Communication Supports 3 axioms—when an Actor receives a message it can: 1.Create new Actors 2.Send messages to Actors it knows 3.Designate how it should handle the next message it receives

14. Actor model Actor Actor Thread pool

15. Akka actor -‐ Definition 15

16. Akka actor -‐ Create 16

17. Akka actor -‐ Send 17

18. Elastic Reactive applications scale up and down to meet demand

19. Elastic • Scalability and elasticity to embrace the Cloud • Leverage all cores via asynchronous programming • Clustered servers support joining and leaving of nodes • More cost-efficient utilization of hardware “Our traffic can increase by as much as 100x for 15 minutes each day. Until a couple of years ago, noon was a stressful time. Nowadays, it’s usually a non-event.” Eric Bowman, VP Architecture, Gilt Groupe 19

20. 20

21. FlightSearchActor 21

22. FlightSearch Actor - I 22

23. FlightSearch Actor - II 23

24. FlightSearchActor 24

25. SearchWorker - I 25

26. SearchWorker - II 26

27. ProviderProxyActor 27

28. ProviderProxy - I 28

29. ProviderProxy - II 29

30. Flight search flow 30

31. Let it crash

32. Reactive applications are architected to handle failure at all levels.

33. Resilient • Failure is embraced as a natural state in the app lifecycle • Resilience is a first-class construct • Failure is detected, isolated, and managed • Applications self heal 33 “The Typesafe Reactive Platform helps us maintain a very aggressive development and deployment cycle, all in a fail-forward manner. It’s now the default choice for developing all new services.” Peter Hausel, VP Engineering, Gawker Media

34. Failure? 34

35. Think Vending Machine

36. Think Vending Machine Coffee Inserts coins Add more coins Programmer Machine Gets coffee

37. Think Vending Machine Service Guy Coffee Inserts coins Programmer Machine Gets coffee Out of coffee beans error Adds more beans OutW of corfofeen begans error

38. The Right Way Supervisor Request Validation Error Client Service Response Application Error Manages Failure

39. Supervision 39

40. A Foo Bar B C B E A C system.actorOf(Props[Foo], “Foo”) context.actorOf(Props[A], “A”) Actor Topology

41. OneForOne

42. AllForOne

43. Isolate failure at all levels • Within one node • Across many nodes (JVMs) • Across many physical servers • Across data centers Reactive Applications 43

44. Scale out

45. 45 Akka clustering

46. Reactive Applications IoT 46

47. Reactive Applications Precision Farming 47 Akka Cluster Journal

48. Code

49. Q & Option[A] @nraychaudhuri

Building Reactive applications with Akka

Building Reactive applications with Akka

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