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
   

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2. About me
   &
   how to get in touch
   @SimonBasle
   

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3. First
   a
   Survey
   

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4. Who Here Uses...
   

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5. Who Here Uses...
   Java 8
   

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6. Who Here Uses...
   Java 8
   RxJava
   

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7. Who Here Uses...
   Java 8
   RxJava
   Reactive Streams
   

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8. Who Here Thinks...
   Reactor is a fork of Atom editor
   

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9. ok bad joke, done
   

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10. the
    Agenda
    

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12. 101
    Reactive
    Programming
    

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13. 101
    Reactive
    Programming
    types &
    operators
    Reactor 3
    

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14. 101
    Reactive
    Programming
    types &
    operators
    Reactor 3
    other beasts
    backpressure
    and
    

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15. 101
    Reactive
    Programming
    types &
    operators
    Reactor 3
    debugging
    testing
    and
    other beasts
    backpressure
    and
    

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16. 101
    Reactive
    Programming
    types &
    operators
    Reactor 3
    and Spring
    Reactor
    debugging
    testing
    and
    other beasts
    backpressure
    and
    

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17. 101
    Reactive
    Programming
    types &
    operators
    Reactor 3
    and Spring
    Reactor
    debugging
    testing
    and
    reactor-netty
    other beasts
    backpressure
    and
    reactor-kafka...
    

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18. Reactive Programming 101
    what does it bring to the table?
    

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19. WHY?
    

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20. WHY?
    because blocking is evil
    

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21. sync/blocking
    main thread processing
    resumes
    I/O
    ! app does
    nothing
    

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22. sync/blocking
    main thread processing
    resumes
    I/O
    BAD
    ! app does
    nothing
    

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23. async & blocking
    main thread wait &
    join
    ! new
    threads,
    costly
    ! complex
    

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24. async & blocking
    main thread wait &
    join
    ! new
    threads,
    costly
    ! complex
    BAD
    

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25. async & nonblocking
    “event loop”
    in non-blocking
    processing
    chunks
    no more threads
    than needed
    

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26. how do you achieve that
    without losing your mind ?
    

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27. Reactive Programming
    

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28. Composing asynchronous
    & event-based sequences,
    using non-blocking operators
    “
    ”
    

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29. without sacrifice
    

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30. without sacrifice
    Callbacks ?
    Futures ?
    easy to block
    hard to compose
    callback hell !
    not readable
    

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31. Pull? Push!
    

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32. Pull? Push!
    

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33. Pull? Push!
    (or actually a little bit of Both)
    

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34. vs
    Iterable
    -
    Iterator
    Publisher
    -
    Subscriber
    

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35. Data in Flux
    

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36. Publisher Subscriber
    push events
    produces consumes
    feedback
    

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37. interfaces from
    Reactive Streams
    spec
    Publisher Subscriber
    feedback
    consumes
    push events
    produces
    

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38. Publisher Subscriber
    push events
    produces consumes
    feedback
    Subscriber
    onNext(T)
    onComplete();
    onError(Throwable);
    

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39. Publisher Subscriber
    produces consumes
    feedback
    0..N elements
    +
    0..1 (complete | error)
    

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40. Publisher Subscriber
    push events
    produces consumes
    feedback
    backpressure
    

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41. Publisher Subscriber
    push events
    produces consumes
    feedback
    can I have an
    API though?
    

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42. Publisher Subscriber
    push events
    produces consumes
    feedback
    

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43. Reactor 3
    types and operators
    

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44. Flux
    for 0..N elements
    

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46. Mono
    for at most 1 element
    

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48. Reactive Streams
    all the way
    

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49. focus on Java 8
    

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50. focus on Java 8
    Duration, CompletableFuture, Streams
    

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51. an Rx-inspired API
    with a vocabulary of operators similar to RxJava...
    

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52. an Rx-inspired API
    ...but not exactly the same
    

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53. Flux/Mono
    generator
    operator
    operator
    operator
    nothing
    happens
    until you
    subscribe
    

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54. Flux/Mono
    generator
    Subscriber
    operator
    operator
    operator
    nothing
    happens
    until you
    subscribe
    

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55. Flux/Mono
    generator
    Subscriber
    operator
    operator
    operator
    per
    Subscription
    state
    Sub
    Sub
    Sub
    

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56. Flux/Mono
    generator
    Subscriber
    operator
    operator
    operator
    data
    flows
    Sub
    Sub
    Sub
    

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57. examples
    

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58. Flux.range
    Subscriber
    map
    filter
    buffer
    

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62. Flux.range
    Subscriber
    map
    filter
    buffer
    

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63. Flux.range
    Subscriber
    map
    filter
    buffer
    

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64. Flux.range
    Subscriber
    map
    filter
    buffer
    

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65. Flux.range
    Subscriber
    map
    filter
    buffer
    

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66. Flux.range
    Subscriber
    map
    filter
    buffer
    

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67. Flux.range
    Subscriber
    map
    filter
    buffer
    

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68. Flux.range
    Subscriber
    map
    filter
    buffer
    

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69. Flux.range(5, 3)
    .map(i -> i + 3)
    .filter(i -> i % 2 == 0)
    .buffer(3)
    

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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]|
    

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71. Flux.from
    Subscriber
    map
    filter
    retry
    Publisher from
    HTTP reactive
    client
    

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73. Flux.from
    Subscriber
    map
    filter
    retry
    Publisher from
    HTTP reactive
    client
    

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74. Flux.from
    Subscriber
    map
    filter
    retry
    Publisher from
    HTTP reactive
    client
    resubscribe
    

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75. go DEEPER!
    async sub-processes with flatMap
    

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77. flatMap(user -> tweetStream(user))
    

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78. flatMap(user -> tweetStream(user))
    

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79. flatMap(user -> tweetStream(user))
    

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80. flatMap(user -> tweetStream(user))
    

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82. & much
    more...
    

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83. threading
    contexts
    

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84. Reactor
    is
    agnostic
    

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85. however it
    facilitates switching
    

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86. Schedulers
    

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87. Schedulers
    elastic, parallel, single, timer...
    

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88. publishOn
    switch rest of the flux on a thread
    

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89. subscribeOn
    make the subscription and request happen
    on a particular thread
    

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90. Flux/Mono
    generator
    operator
    subscribeO
    n
    operator
    publishOn
    operator
    operator
    Subscriber
    Sub
    Sub
    Sub
    Sub
    Sub
    Sub
    

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91. Flux/Mono
    generator
    operator
    subscribe
    On
    operator
    publish
    On
    operator
    operator
    Subscriber
    Sub
    Sub
    Sub
    Sub
    Sub
    Sub
    

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92. Flux/Mono
    generator
    operator
    subscribeO
    n
    operator
    publishOn
    operator
    operator
    Subscriber
    Sub
    Sub
    Sub
    Sub
    Sub
    Sub
    

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93. Flux/Mono
    generator
    operator
    subscribeO
    n
    operator
    publishOn
    operator
    operator
    Subscriber
    Sub
    Sub
    Sub
    Sub
    Sub
    Sub
    

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94. Flux/Mono
    generator
    operator
    subscribeO
    n
    operator
    publishOn
    operator
    operator
    Subscriber
    Sub
    Sub
    Sub
    Sub
    Sub
    Sub
    

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95. Flux/Mono
    generator
    operator
    subscribeO
    n
    operator
    publishOn
    operator
    operator
    Subscriber
    Sub
    Sub
    Sub
    Sub
    Sub
    Sub
    

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96. Testing & Debugging
    in an asynchronous world
    

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97. Testing a Publisher
    StepVerifier
    

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98. Testing a Publisher
    with Virtual Time support
    

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99. Simulate a source
    TestPublisher
    

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100. Debugging Issues
     stacktraces get hard to decipher
     

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101. usually just show
     where Subscription happens
     

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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)
     

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103. Find where the Flux
     was instantiated (assembly)
     

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104. Checkpoint()
     or full assembly tracing
     

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105. costly!
     Checkpoint()
     or full assembly tracing
     

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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)
     

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107. BACKPRESSURE
     and other beasts
     

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108. Publisher Subscriber
     subscribe
     

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109. Publisher Subscriber
     push data as fast as possible
     

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110. Publisher Subscriber
     subscribe
     with small request
     (eg. 1)
     

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111. Publisher Subscriber
     1 onNext
     

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112. Publisher Subscriber
     request more
     (eg. 2)
     

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113. Publisher Subscriber
     2 onNext
     

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114. Publisher Subscriber
     backpressure
     

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115. other ways of dealing with backpressure
     eg. drop, buffer...
     

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116. internal
     optimisations
     

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117. macro FUSION
     avoids unnecessary request back-and-forth
     

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118. micro FUSION
     share internal structures for less allocation
     

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119. lock free operators
     

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120. lock free operators
     and Work Stealing
     CPU 1
     CPU 2
     CPU 3
     CPU 4
     CPU 5
     

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121. Reactor and
     Spring
     

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122. Reactor and
     Spring
     and do I need Spring to use Reactor ?
     

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123. NO philosoraptor you don’t
     

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124. Reactor 3
     is a dependency of
     Spring 5
     not the other way around
     

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126. Java 8
     baseline
     

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127. reactive
     focus
     

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128. new WEB stack
     WebFlux
     

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129. @RestController(“/user”)
     public class UserController {
     @GetMapping(“/{id}”)
     Mono getUser(String id) {...}
     }
     

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130. functional option
     for Routing
     

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131. Spring Data
     reactive repositories
     

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132. @GetMapping(“/{id}”)
     Mono getUser(String id) {
     return reactiveRepo.findOne(id);
     }
     

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133. Reactor and the Network
     reactor-netty
     

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134. reactor-netty
     builds on Netty to provide
     reactive I/O
     

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135. Client / Server
     

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136. TCP
     or udp
     

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137. Http
     and WebSockets
     

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138. HttpServer.create(0)
     .newHandler((in, out) -> out
     .sendWebsocket((i, o) ->
     o.options(opt -> opt.flushOnEach())
     .sendString(Flux.just("test")
     .delayElementsMillis(100)
     .repeat())
     )
     )
     .block();
     

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139. still a bit low level
     

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140. still a bit low level
     

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141. reactor-kafka
     topics as
     Flux
     

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142. reactive API
     over Kafka Producer / Consumer
     

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143. send(Flux)
     into Kafka
     

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144. Flux receive()
     from Kafka
     

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145. (currently in MILESTONE 2)
     

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146. Questions?
     

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147. Thanks!
     

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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.
     

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