Reactor 3

Reactor 3, a reactive foundation for the JVM

Introduction to reactive programming, Reactor 3 and a bit of Spring 5.

(note: presentation will be re-uploaded if it is updated, so it might not 100% correspond to the version I used at talks in the past)

Transcript

1. Reactor 3 a Reactive foundation for the JVM
2. About me & how to get in touch @SimonBasle
3. First a Survey
4. Who Here Uses...
5. Who Here Uses... Java 8
6. Who Here Uses... Java 8 RxJava
7. Who Here Uses... Java 8 RxJava Reactive Streams
8. Who Here Thinks... Reactor is a fork of Atom editor
9. ok bad joke, done
10. the Agenda
12. 101 Reactive Programming
13. 101 Reactive Programming types & operators Reactor 3
14. 101 Reactive Programming types & operators Reactor 3 other beasts backpressure and
15. 101 Reactive Programming types & operators Reactor 3 debugging testing and other beasts backpressure and
16. 101 Reactive Programming types & operators Reactor 3 and Spring Reactor debugging testing and other beasts backpressure and
17. 101 Reactive Programming types & operators Reactor 3 and Spring Reactor debugging testing and reactor-netty other beasts backpressure and reactor-kafka...
18. Reactive Programming 101 what does it bring to the table?
19. WHY?
20. WHY? because blocking is evil
21. sync/blocking main thread processing resumes I/O ! app does nothing
22. sync/blocking main thread processing resumes I/O BAD ! app does nothing
23. async & blocking main thread wait & join ! new threads, costly ! complex
24. async & blocking main thread wait & join ! new threads, costly ! complex BAD
25. async & nonblocking “event loop” in non-blocking processing chunks no more threads than needed
26. how do you achieve that without losing your mind ?
27. Reactive Programming
28. Composing asynchronous & event-based sequences, using non-blocking operators “ ”
29. without sacrifice
30. without sacrifice Callbacks ? Futures ? easy to block hard to compose callback hell ! not readable
31. Pull? Push!
32. Pull? Push!
33. Pull? Push! (or actually a little bit of Both)
34. vs Iterable - Iterator Publisher - Subscriber
35. Data in Flux
36. Publisher Subscriber push events produces consumes feedback
37. interfaces from Reactive Streams spec Publisher Subscriber feedback consumes push events produces
38. Publisher Subscriber push events produces consumes feedback Subscriber<T> onNext(T) onComplete(); onError(Throwable);
39. Publisher Subscriber produces consumes feedback 0..N elements + 0..1 (complete | error)
40. Publisher Subscriber push events produces consumes feedback backpressure
41. Publisher Subscriber push events produces consumes feedback can I have an API though?
42. Publisher Subscriber push events produces consumes feedback
43. Reactor 3 types and operators
44. Flux<T> for 0..N elements
46. Mono<T> for at most 1 element
48. Reactive Streams all the way
49. focus on Java 8
50. focus on Java 8 Duration, CompletableFuture, Streams
51. an Rx-inspired API with a vocabulary of operators similar to RxJava...
52. an Rx-inspired API ...but not exactly the same
53. Flux/Mono generator operator operator operator nothing happens until you subscribe
54. Flux/Mono generator Subscriber operator operator operator nothing happens until you subscribe
55. Flux/Mono generator Subscriber operator operator operator per Subscription state Sub Sub Sub
56. Flux/Mono generator Subscriber operator operator operator data flows Sub Sub Sub
57. examples
58. Flux.range Subscriber map filter buffer
62. Flux.range Subscriber map filter buffer
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(5, 3) .map(i -> i + 3) .filter(i -> i % 2 == 0) .buffer(3)
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. Flux.from Subscriber map filter retry Publisher from HTTP reactive client
73. Flux.from Subscriber map filter retry Publisher from HTTP reactive client
74. Flux.from Subscriber map filter retry Publisher from HTTP reactive client resubscribe
75. go DEEPER! async sub-processes with flatMap
77. flatMap(user -> tweetStream(user))
78. flatMap(user -> tweetStream(user))
79. flatMap(user -> tweetStream(user))
80. flatMap(user -> tweetStream(user))
82. & much more...
83. threading contexts
84. Reactor is agnostic
85. however it facilitates switching
86. Schedulers
87. Schedulers elastic, parallel, single, timer...
88. publishOn switch rest of the flux on a thread
89. subscribeOn make the subscription and request happen on a particular thread
90. Flux/Mono generator operator subscribeO n operator publishOn operator operator Subscriber Sub Sub Sub Sub Sub Sub
91. Flux/Mono generator operator subscribe On operator publish On operator operator Subscriber Sub Sub Sub Sub Sub Sub
92. Flux/Mono generator operator subscribeO n operator publishOn operator operator Subscriber Sub Sub Sub Sub Sub Sub
93. Flux/Mono generator operator subscribeO n operator publishOn operator operator Subscriber Sub Sub Sub Sub Sub Sub
94. Flux/Mono generator operator subscribeO n operator publishOn operator operator Subscriber Sub Sub Sub Sub Sub Sub
95. Flux/Mono generator operator subscribeO n operator publishOn operator operator Subscriber Sub Sub Sub Sub Sub Sub
96. Testing & Debugging in an asynchronous world
97. Testing a Publisher StepVerifier
98. Testing a Publisher with Virtual Time support
99. Simulate a source TestPublisher
100. Debugging Issues stacktraces get hard to decipher
101. usually just show where Subscription happens
102. java.lang.IndexOutOfBoundsException: Source emitted more than one item at reactor.core.publisher.MonoSingle$SingleSubscriber.onNext(MonoSingle.java:120) at reactor.core.publisher.FluxOnAssembly$OnAssemblySubscriber.onNext(FluxOnAssembly.java:314) ... ... at reactor.core.publisher.Mono.subscribeWith(Mono.java:2668) at reactor.core.publisher.Mono.subscribe(Mono.java:2629) at reactor.core.publisher.Mono.subscribe(Mono.java:2604) at reactor.core.publisher.Mono.subscribe(Mono.java:2582) at reactor.guide.GuideTests.debuggingActivated(GuideTests.java:727)
103. Find where the Flux was instantiated (assembly)
104. Checkpoint() or full assembly tracing
105. costly! Checkpoint() or full assembly tracing
106. Assembly trace from producer [reactor.core.publisher.MonoSingle] : reactor.core.publisher.Flux.single(Flux.java:5335) reactor.guide.GuideTests.scatterAndGather(GuideTests.java:689) reactor.guide.GuideTests.populateDebug(GuideTests.java:702)
107. BACKPRESSURE and other beasts
108. Publisher Subscriber subscribe
109. Publisher Subscriber push data as fast as possible
110. Publisher Subscriber subscribe with small request (eg. 1)
111. Publisher Subscriber 1 onNext
112. Publisher Subscriber request more (eg. 2)
113. Publisher Subscriber 2 onNext
114. Publisher Subscriber backpressure
115. other ways of dealing with backpressure eg. drop, buffer...
116. internal optimisations
117. macro FUSION avoids unnecessary request back-and-forth
118. micro FUSION share internal structures for less allocation
119. lock free operators
120. lock free operators and Work Stealing CPU 1 CPU 2 CPU 3 CPU 4 CPU 5
121. Reactor and Spring
122. Reactor and Spring and do I need Spring to use Reactor ?
123. NO philosoraptor you don’t
124. Reactor 3 is a dependency of Spring 5 not the other way around
126. Java 8 baseline
127. reactive focus
128. new WEB stack WebFlux
129. @RestController(“/user”) public class UserController { @GetMapping(“/{id}”) Mono<User> getUser(String id) {...} }
130. functional option for Routing
131. Spring Data reactive repositories
132. @GetMapping(“/{id}”) Mono<User> getUser(String id) { return reactiveRepo.findOne(id); }
133. Reactor and the Network reactor-netty
134. reactor-netty builds on Netty to provide reactive I/O
135. Client / Server
136. TCP or udp
137. Http and WebSockets
138. HttpServer.create(0) .newHandler((in, out) -> out .sendWebsocket((i, o) -> o.options(opt -> opt.flushOnEach()) .sendString(Flux.just("test") .delayElementsMillis(100) .repeat()) ) ) .block();
139. still a bit low level
140. still a bit low level
141. reactor-kafka topics as Flux<T>
142. reactive API over Kafka Producer / Consumer
143. send(Flux) into Kafka
144. Flux receive() from Kafka
145. (currently in MILESTONE 2)
146. Questions?
147. Thanks!
148. Credits • Springfield Plant: copyright FOX • Raised Hand: CC0 (via Pixabay) • Checklist: CC-By Crispy (via Flickr) • Robot Devil: copyright FOX • Volume Knob: CC0 (via Pixabay) • Camel Shape: CC0 (via Pixabay) • Dromedary Shape: CC-By-SA USPN,Whidou (via Wikimedia) • Dam: CC-By-SA Matthew Hatton (via geograph.org.uk) • Cogs: CC0 (via publicdomainpictures.net) • Thread Balls: CC0 (via Pixabay) • The Fortune Teller: Georges de la Tour (public domain) • Microphone: CC0 (via Pexels) • End Sands: CC0 (via Pixabay) • logos: Pivotal, Spring, Twitter and Github logo copyright their respective companies.