This document provides an introduction to Akka actors. It discusses how actors provide a model for building concurrent and distributed applications by avoiding shared mutable state and instead using message passing. Actors communicate asynchronously by message passing and handle errors through a supervision hierarchy. The document outlines several features of the actor model including load balancing, parallelization, and error handling.

1. An introduction to
Actors
Akka
with
Johan Andrén
johan.andren@mejsla.se | @apnylle

2. Moores law
2,6 billions
1 million
2300
1971
1990
today

3. Oh, No Problems!

4. Oh No, Problems!
•
•
•
•
•
•
Race conditions
Data corruption
Deadlocks
Thread contention
Livelocks
Priority Inversion

5. Concurrency is HARD
•
•
•
•
To write
To test
To debug
To reason about
We need a better model!

7. B
C
D
A
F
E

8. event driven
systems with
ACTORS

10. State
Inbox
The only way to
interact from
outside
Behaviour

11. •
•
•
•
•
Single execution flow model
No shared _mutable_ state
Lightweight
Loose coupling
Easy to test

12. Actor A
Actor B

13. One way communication
Actor A
Actor B

14. React, don’t wait
Actor A
Actor B

15. Load balancing
Actor A
Actor B1
router
Actor B2

16. Pipe/Filter
Actor A
Actor F
(filter)
Actor B

17. Parallellize
Actor C1
Actor A
Actor B
(chef)
Actor C2
Actor C2

18. •
•
•
No work, no thread used!
Async - never actively wait
Loose coupling

19. JVM
B
C
D
A
F
E

20. JVM 1
B
C
JVM 2
D
A
F
E

21. The same same
•
•
•
Two actors on one core
Two actors on separate cores
Two actors on separate servers

22. Error handling
in Actor systems

24. Traditional model
•
•
•
Leaking information between tiers
Impossible to detect simultaneous
errors
The receiver does not know how to
handle the errors!

25. Error handling with Actors
(parent)
Actor A
Actor X
Actor Z

26. Error handling with Actors
(parent)
Actor A
Actor X
Actor Z

27. Error handling with Actors
Actor A
Actor X
Actor Z

28. ”Supervision”
•
•
•
•
Compartmentilization
What goes back is explicit
Separating error handling and
business logic
Can detect simultaneous errors

29. But
Wait, there is more!
•
•
•
•
•
STM
Remoting
Clustring with no SPoF
MQs integration
Eventbus
Website: akka.io

30. Try it out!
Typesafe Activator
typesafe.com

31. Recap
•
•
•
•
Simple but powerful model
Lightweight and fast
Loose coupling
Resiliency
Johan Andrén
johan.andren@mejsla.se | @apnylle

32. Questions?
Johan Andrén
johan.andren@mejsla.se | @apnylle