Actor Model is one of the concurrency models in computing. This presentation covers basic concepts, ecosystem and use cases in actor model.

1. ACTOR MODEL
A DIFFERENT CONCURRENCY APPROACH
Emre Akış
@akisemre

2. • CONCURRENCY MODELS
• HISTORY
• CONCEPTS
• +‘s & -’s
• ECOSYSTEM
• RESOURCES

3. • CONCURRENCY MODELS
• HISTORY
• CONCEPTS
• +‘s & -’s
• ECOSYSTEM
• RESOURCES

4. • Sequential
• Concurrent
• Parallel
• Mixed
* http://leakfromjavaheap.blogspot.com.tr/2016/05/concurrency-vs-parallelism.html

5. • CONCURRENCY MODELS
• HISTORY
• CONCEPTS
• +‘s & -’s
• ECOSYSTEM
• RESOURCES

6. • 1973, Carl Hewitt
• 1986, Gul Agha
• 1995, Ericsson : First Commercial Use
• 2009, Jonas Boner

7. • CONCURRENCY MODELS
• HISTORY
• CONCEPTS
• +‘s & -’s
• ECOSYSTEM
• RESOURCES

8. • The actor model in computer science is
a mathematical model of concurrent
computation that treats "actors" as the
universal primitives of concurrent
computation.
• In response to a message that it receives, an
actor can: make local decisions, create more
actors, send more messages, and determine
how to respond to the next message
received.

9. • Encapsulated state
• Behaviour
• Indepedent control
• Mailbox
http://brianrepko.github.io/presentation-big-data-bioinfo/images/actor-model.png

10. Address
• Identifies an actor
• May also represent a proxy/forwarder to an an Actor
• Contains location and transport information
• Location transparency

11. Address
• One actor may represent many actors (pool)
• One actor may have many address
Load
Balancer
Actor
Actor
Actor
Actor
Machine 1
Machine 2
Actor Actor Actor
X
Y
Z

12. • Each actor has its own process (not intended
as an OS process) and they don’t share state
between them.
• Actors can change their own states.
• Actors can create other actors and when they
do that they receive back the new actor
address.
• Actor exchange messages in an asynchronous
fashion.

13. Handling Errors
• Supervision : The running state of an actor is
monitored and managed by another actor (Supervisor)
https://petabridge.com/blog/how-actors-recover-from-failure-hierarchy-and-supervision/

14. • Address does not change during restarts
• Mailboxes are persisted outside the actor
instances
http://getakka.net/docs/concepts/actors

15. • CONCURRENCY MODELS
• HISTORY
• CONCEPTS
• +‘s & -’s
• ECOSYSTEM
• RESOURCES

16. • No shared memory and therefore locking is
not required.
• Race conditions greatly reduced.
• It greatly simplifies the control flow of a
program, each actor has its own process
(flow of control)
• Easy to distribute, across cores, across
program boundaries, across machines.
• It simplifies error handling code.
• It makes it easier to build fault-tolerant
systems.

17. • Too many actors ( Tracing )
• Testing
• Debugging
• Don’t work well when
• shared state needed
• need to achieve global consensus
• synchronous behaviour is needed

18. • CONCURRENCY MODELS
• HISTORY
• CONCEPTS
• +‘s & -’s
• ECOSYSTEM
• RESOURCES

19. • T https://azure.microsoft.com/en-us/blog/use-actors-to-talk-to-millions/
• F https://www.facebook.com/notes/facebook-engineering/facebook-chat/14218138919/
• W https://www.wired.com/2015/09/whatsapp-serves-900-million-users-50-engineers/
• sas

22. • CONCURRENCY MODELS
• HISTORY
• CONCEPTS
• +‘s & -’s
• ECOSYSTEM
• RESOURCES

23. • https://en.wikipedia.org/wiki/Actor_model
• http://wiki.c2.com/?ActorsModel
• Hewitt, Meijer and Szyperski: The Actor Model @
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