Reactive Spring Workshop @Javaland

Slides introducing reactive programming with Spring and Reactor at the Javaland "Reactive Spring" workshop, given March 2017.

Transcript

1. Reactive Spring Workshop
2. Reactive Programming 101 what does it bring to the table?
3. WHY?
4. WHY? because blocking is evil
5. sync/blocking main thread processing resumes I/O ! app does nothing
6. sync/blocking main thread processing resumes I/O BAD ! app does nothing
7. async & blocking main thread wait & join ! new threads, costly ! complex
8. async & blocking main thread wait & join ! new threads, costly ! complex BAD
9. async & nonblocking “event loop” in non-blocking processin g chunks no more threads than needed
10. how do you achieve that without losing your mind ?
11. Reactive Programming
12. Composing asynchronous & event-based sequences, using non-blocking operators “ ”
13. without sacrifice
14. without sacrifice Callbacks ? Futures ? easy to block hard to compose callback hell ! not readable
15. Pull? Push!
16. Pull? Push!
17. vs Iterable - Iterator Publisher - Subscriber
18. Data in Flux
19. Publisher Subscriber push events produces consumes feedback
20. interfaces from Reactive Streams spec Publisher Subscriber feedback consumes push events produces
21. Publisher Subscriber push events produces consumes feedback Subscriber<T> onNext(T) onComplete(); onError(Throwable);
22. Publisher Subscriber produces consumes feedback 0..N elements + 0..1 (complete | error)
23. Publisher Subscriber push events produces consumes feedback backpressure
24. Publisher Subscriber push events produces consumes feedback can I have an API though?
25. Publisher Subscriber push events produces consumes feedback
26. Reactor 3 types and operators
27. Flux<T> for 0..N elements
29. Mono<T> for at most 1 element
31. Reactive Streams all the way
32. focus on Java 8
33. focus on Java 8 Duration, CompletableFuture, Streams
34. an Rx-inspired API with a vocabulary of operators similar to RxJava...
35. an Rx-inspired API ...but not exactly the same
36. Flux/Mono generator operator operator operator nothing happens until you subscribe
37. Flux/Mono generator Subscriber operator operator operator nothing happens until you subscribe
38. Flux/Mono generator Subscriber operator operator operator per Subscription state Sub Sub Sub
39. Flux/Mono generator Subscriber operator operator operator data flows Sub Sub Sub
40. “elements of functional programming”
41. threading contexts
42. Reactor is agnostic
43. however it facilitates switching
44. Schedulers
45. Schedulers elastic, parallel, single, timer...
46. publishOn switch rest of the flux on a thread
47. subscribeOn make the subscription and request happen on a particular thread
48. Flux/Mono generator operator subscribeOn operator publishOn operator operator Subscriber Sub Sub Sub Sub Sub Sub
49. Flux/Mono generator operator subscribe On operator publish On operator operator Subscriber Sub Sub Sub Sub Sub Sub
50. Flux/Mono generator operator subscribeOn operator publishOn operator operator Subscriber Sub Sub Sub Sub Sub Sub
51. Flux/Mono generator operator subscribeOn operator publishOn operator operator Subscriber Sub Sub Sub Sub Sub Sub
52. Flux/Mono generator operator subscribeOn operator publishOn operator operator Subscriber Sub Sub Sub Sub Sub Sub
53. Flux/Mono generator operator subscribeOn operator publishOn operator operator Subscriber Sub Sub Sub Sub Sub Sub
54. CODING TIME!
56. Bonus Slides operator step-by-step examples, backpressure
57. map, filter, buffer
58. Flux.range Subscriber map filter buffer
62. Flux.range(5, 3) .map(i -> i + 3) .filter(i -> i % 2 == 0) .buffer(3)
63. Flux.range Subscriber map filter buffer
64. Flux.range Subscriber map filter buffer
65. Flux.range Subscriber map filter buffer
66. Flux.range Subscriber map filter buffer
67. Flux.range Subscriber map filter buffer
68. Flux.range Subscriber map filter buffer
69. Flux.range Subscriber map filter buffer
70. Flux.range(5, 3) .map(i -> i + 3) .filter(i -> i % 2 == 0) .buffer(3) 5, 6, 7 | 8, 9, 10 | 8, 10 | [8,10]|
71. retry
72. Flux.from Subscriber map filter retry Publisher from HTTP reactive client
74. Flux.from Subscriber map filter retry Publisher from HTTP reactive client
75. Flux.from Subscriber map filter retry Publisher from HTTP reactive client resubscribe
76. Trickier: flatMap async sub-processes
78. flatMap(user -> tweetStream(user))
79. flatMap(user -> tweetStream(user))
80. flatMap(user -> tweetStream(user))
81. flatMap(user -> tweetStream(user))
83. & much more...
84. backpressure the "volume control"
85. Publisher Subscriber subscribe
86. Publisher Subscriber push data as fast as possible
87. Publisher Subscriber subscribe with small request (eg. 1)
88. Publisher Subscriber 1 onNext
89. Publisher Subscriber request more (eg. 2)
90. Publisher Subscriber 2 onNext
91. Publisher Subscriber backpressure
92. other ways of dealing with backpressure eg. drop, buffer...
93. Credits ! Robot Devil: copyright FOX ! Volume Knob: CC0 (via Pixabay) ! Camel Shape: CC0 (via Pixabay) ! Dromedary Shape: CC-By-SA USPN,Whidou (via Wikimedia) ! Thread Balls: CC0 (via Pixabay) ! Coding Time: derived from KEMUDA Computer Lab (CC-By-SA Andy.aug, via Wikimedia) ! Sound Table: CC0 (via Pexels) ! Dam: CC-By-SA Matthew Hatton (via geograph.org.uk) ! logos: Pivotal, Spring, Twitter and Github logo copyright their respective companies.