Akka Fundamentals
Download as PPTX, PDF•3 likes•427 views
This document provides an overview of Akka fundamentals including: - The actor model which uses message passing between encapsulated state and behavior units to achieve concurrency - The Akka actor API for building fault tolerant distributed applications in Scala and Java - Fault tolerance techniques in Akka like supervision which allows actors to monitor and respond to failures of child actors - Routing which provides abstractions for distributing messages to multiple receiver actors
Akka Fundamentals
- 2. Agenda • Why Akka? • Actor Model • Actor API (Scala/Java) • Fault Tolerance - Supervision • Routing
- 8. Users: - John Snow - Bran Stark - Tyrion Lannister
- 10. Locks
- 12. • Error Prone • Hard to reason about • Hard to implement • Hard to debug • Ugly • Low level • …
- 13. "All problems in computer science can be solved by another level of indirection" David Wheeler
- 14. The Actor Model
- 15. A selection of events in the history of Actors: • Carl Hewitt et al, 1973: Actors invented for research on AI • Gul Agha, 1986: Actor languages and communication patterns • Ericsson, 1995: first commercial use in Erlang/OTP for telecom platform • Phillip Haller, 2006: implemented in the Scala stdlib • Jonas Boner, 2009: creation of Akka Principles of Reactive Programming, Week 5 Part 1
- 16. An Actor
- 18. What’s the time?
- 20. What’s the time? 13:30 Message Passing
- 21. An Actor: • Encapsulates state • Has a behaviour (logic) • Communicates via async messages
- 22. The Actor API
- 33. Fault Tolerance
- 40. We’ve crossed thread boundaries
- 41. This async boundary is explicit and a first class citizen in Akka
- 42. • All Actor communication is message based • Errors are messages
- 43. Akka guides you in building fault tolerant applications by embracing failure. “Let it crash”
- 44. Akka’s fault tolerance policy: • supervised Actors form a tree structure • the supervisor needs to create its child • failed Actor is terminated or restarted • decision must be taken by one other Actor
- 45. Supervision
- 46. Boss Worker A Worker B Worker C Actors form hierarchies
- 47. Worker A Worker B Worker C Boss
- 49. Decider
- 51. Boss Worker A Worker B Worker C
- 52. Boss Worker A Worker B Worker C
- 53. Boss Worker A Worker B Worker C
- 54. Boss Worker A Worker B Worker C
- 55. Boss Worker A Worker B Worker C
- 58. Boss + Workers System Error Kernel Pattern
- 59. Routing
- 60. An abstraction over the delivery of messages from a Sender to Receiver(s)
- 62. Router
- 63. • Akka provides several builtin Routers • You may of course define your own
- 64. Round Robin Router D. Wyatt - Akka Concurrency
- 65. Broadcast Router D. Wyatt - Akka Concurrency
- 66. Smallest Mailbox Router D. Wyatt - Akka Concurrency
- 67. Two types of routers: 1. Pool • Router creates routees 2. Group • You create routees and pass them in
- 68. Pool
- 70. Programatically
- 71. Group
- 73. Programatically
Editor's Notes
- #4: “Free lunch is over” - 2005 Write program ’80 => come back later it’s faster Write program ’05 => come back later it’s the same Need to use multiple cores
- #6: Simpler to show with Java
- #10: Between these two instructions there’s a shitload of CPU cycles
- #14: Let someone else go through the pain, once We benefit from the abstraction
- #17: An actor by himself can’t do much
- #33: Meaning gets lost in syntax
- #59: Delegate dangerous work do the bottom Keep important state as high as possible
- #61: Does not add any expressive power We can do this ourselves Just easier to use a provided thing
- #62: We have to define and manipulate these arrows manually, overselves. Let’s try do it a better way
- #63: Router is not an Actor
- #66: If every actor is interested in a message If you don’t know whose interested in a message Notifier
- #67: Load balancing
- #69: router creates all children hence is their parent and supervisor
- #70: Send messages to router, router forwards to routees Router does not change original sender
- #74: Router uses ActorSelection to get ActorRefs Must create them ourselves
- #75: Here we can set up any structure we wish