Reactive Programming

• It is a declarative programming paradigm concerned with data streams and the propagation of change.
• It is declarative as opposed to imperative - where we need to tell the steps
• With this paradigm, it’s possible to express static (eg. arrays) or dynamic (eg. event emitters) data streams with ease
• It uses two design patterns:
  • Iterator Pattern (data is pulled from iterator)
  • Observer Pattern (data is pushed to observer)
• It is event based compared to message based in reactive systems
  • https://stackoverflow.com/questions/1659351/message-driven-vs-event-driven-approaches-to-application-integration
• See also Reactive_Systems_and_EDA

Reactive Streams Specification

• Ref:
  • https://www.reactive-streams.org/
  • https://www.wikiwand.com/en/Reactive_Streams
• Implementations/Inspirations:
  • ReactiveX: https://reactivex.io/languages.html
    • RxJava (2.0+ version is based on reactive streams spec)
    • RxJS
  • Project Reactor: https://projectreactor.io/ (https://github.com/reactor/reactor-core)
  • Akka Streams

Backpressure

• It happens when publisher is sending too fast, but the subscriber is not able to keep up