The talk was given on local JUG meetup back in 2014. The purpose of the talk was to give an overview of the Akka library for the Java-programmers audience who have never used it before. My first appearance as a public speaker

1. AKKurate
twist522@gmail.com
JUG Lviv

2. outline
Problems to solve
Actor Model
Java & Scala actors
Fault-tolerance
Scaling, Remoting
Reactiveness
Some best practices

3. The Problem
• highly concurrent
• scalable
• fault-tolerant

4. AKKA

6. Program at a higher level

7. Scaling up & out
& down & .. whatever

8. Automatic Replication & Distribution
for fault tolerance & scalability

9. Automatic Load Balancing

10. Modules
• akka-kernel
• akka-actor
• akka-camel
• akka-remote
• akka-cluster
• akka-persistence
• akka-stream
• …

11. Actor Model
Back into the 70’s
actors could
• perform
• create another actors
• send messages
• become
Carl Hewitt

12. Actor
• one msg at a time
• in one thread
• msgs in order
• small (~2.5M per Gb)

13. Core operations
0. Define
1. Create
2. Send
3. Become
4. Supervise

14. 0. Define

15. In Scala

16. 1. Create

17. Actor hierarchy

18. 2. Send

19. Full example

20. In Scala

21. Hot Swap

22. In Scala

23. ask

24. Futures

25. Supervision & Monitoring
• failures happen
• application should self-heal
• each actor have supervisor
• supervisor handles failures
– RESUME
– RESTART
– STOP
– ESCALATE

26. Failure management
money
snack
not enough!FATAL ERROR
FATAL ERROR
supervisor

27. Supervisor hierarchies
• One-for-one strategy
• All-for-one strategy

28. Root actors

29. 4. Supervise

30. Death Watch

31. Failure management in Java

32. Load Balancing
• scaling up – routers
• scaling out – akka-cluster

33. Routers

34. From config

35. Routers
• Random
• Round-robin
• Smallest messagebox
• Broadcast
• ScatterGatherFirstCompletedOf
• …

36. Remote Deployment

37. Lookup

38. Note on reactiveness

39. Reactive manifesto

40. Actors should do only one thing
• Single responsibility principle
• Create specific supervisors
• Keep the error kernel simple

41. Avoid blocking

42. Don’t expose actors
• Avoid using this
• Don’t close over variables
• Use immutable messages with immutable
data

43. E0
F