Reactive programming using rx java & akka actors - pdx-scala - june 2014
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Reactive programming is an event-driven paradigm focused on data flow and treating code as a set of behaviors in response to events. RxJava is a library that uses observable sequences to compose asynchronous and event-based programs in a reactive style. It provides operators like map, flatMap, and filter to transform streams of events. Akka implements the actor model with actors that react to immutable messages in isolation through message passing. Both RxJava and Akka support reactive principles like scalability, resilience and responsiveness but require additional work.
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Reactive programming using rx java & akka actors - pdx-scala - june 2014
- 1. Reactive Programming using RxJava & Akka Actors Thomas Lockney (@tlockney) PDXScala June 14, 2014
- 3. Reactive programming is… ● A programming paradigm ● About data-flow ● Not really anything new
- 4. Reactive programming is... ● Event-driven ● Scalable ● Resilient ● Responsive (the definition via the manifesto, anyway)
- 5. Reorganizing our thoughts a bit... ● Think in terms of discrete events ● Code in terms of behaviors ○ reacting to events ● The system state changes over time based on the flow of events
- 6. A brief digression... Amdahl’s law (paraphrased): The maximum increase in speed of a program is limited by the sequential portions of the code.
- 7. A brief digression... Amdahl’s law (paraphrased): If you have a program that runs for 4 hours, but 1 hour of runtime is necessarily serial, your program will have at most a 4x speedup with parallelization.
- 8. Amdahl’s law
- 9. The thing about Amdahl’s law This is death by a thousand cuts. Every line of code is subject to this rule!
- 10. Some principles... ● Keep your data immutable ● Share nothing ● Blocking is bad!
- 12. ● Immutable data structures ● Referential transparency ● First-class functions … this gives you ... Once you have:
- 14. well... Functional Programming in the small
- 15. RxJava “a library for composing asynchronous and event-based programs using observable sequences for the Java VM”
- 16. My translation: RxJava A library for composing behaviors applied to event streams. note: when I say behaviors, think referentially-transparent functions.
- 17. Marble Diagrams
- 18. Observable ● The “dual” of Iterable ● Or an Observer for sequences ● Somewhat similar to a Future ○ but, again, supports sequences
- 19. Observable Basic mechanics ● onNext() ● onError() ● onComplete()
- 20. Functional Composition ● map() ● flatMap() ● filter()
- 21. map()
- 22. flatMap()
- 23. filter()
- 24. Creating Observables ● Observable.from(...), Observable.just(...), Observable.range(...), etc. ● Implement the Observable interface ○ explicit calls to onNext(), onError(), onComplete()
- 25. Observer & Subscriber Observer ● interface for handling Observables onNext, onError, onComplete Subscriber ● represents a subscription to an observable
- 26. Demo time!
- 27. RxJava is Reactive ● event-based (data-flows) ● scalable* ● resilient* (???) ● responsive* (???) * - requires some additional work on your end ??? - the story here is not entirely clear or potentially even available in current releases
- 28. Akka & the actor model
- 29. Actors (the Actor model) Defined by three traits ● a behavior (reacts to events) ● an state model ● send/receive (immutable) messages
- 30. Actors ● messages are processed sequentially ● multiple actors can be working at the same time ● actors are not threads ● an actor can block (but should avoid it) ● no shared state
- 31. Actor System ● actors interact ● actors exist together within an actor system ● the system defines the outermost bounds
- 32. Akka ● Scala-based actor model toolkit ● Provides a lot of extras ● We won’t be talking about those
- 33. Akka ● Supervisors ○ provide exception handling ○ “let it crash” ○ orthogonal to actor behavior ● Location transparency ○ abstracts the idea of “where” an actor lives
- 34. Akka ● Mailboxes ● Routing ○ e.g., round-robin, smallest mailbox, etc. ● Dispatching ○ essentially how to allocate thread resources
- 35. Demo time!
- 36. Akka is Reactive ● event-based ● resilient/fault-tolerant ● easily scalable* ● responsive* * - requires some additional work on your end
- 37. Reactive Streams
- 38. Reactive Streams … I wish I had time … ;~)