projectreactor.io reactor3 intro

Transcript

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2. the
   Agenda
   

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

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

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6. WHY?
   because blocking is evil
   

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

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

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

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

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11. Reactive Programming
    

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

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13. without sacrifice
    

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

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15. Pull? Push!
    

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16. Pull? Push!
    

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

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18. vs
    Iterable
    -
    Iterator
    Publisher
    -
    Subscriber
    

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19. Data in Flux
    

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20. Publisher Subscriber
    push events
    produces consumes
    feedback
    

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

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

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

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24. Publisher Subscriber
    push events
    produces consumes
    feedback
    backpressure
    

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

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26. Publisher Subscriber
    push events
    produces consumes
    feedback
    

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27. Reactor 3
    types and operators
    

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28. Flux
    for 0..N elements
    

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30. Mono
    for at most 1 element
    

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32. Reactive Streams
    all the way
    

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33. focus on Java 8
    

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34. focus on Java 8
    Duration, CompletableFuture, Streams
    

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

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

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

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

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

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

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41. examples
    

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42. Flux.range
    Subscriber
    map
    filter
    buffer
    

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

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47. Flux.range
    Subscriber
    map
    filter
    buffer
    

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48. Flux.range
    Subscriber
    map
    filter
    buffer
    

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49. Flux.range
    Subscriber
    map
    filter
    buffer
    

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50. Flux.range
    Subscriber
    map
    filter
    buffer
    

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51. Flux.range
    Subscriber
    map
    filter
    buffer
    

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52. Flux.range
    Subscriber
    map
    filter
    buffer
    

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53. Flux.range
    Subscriber
    map
    filter
    buffer
    

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54. 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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55. Flux.from
    Subscriber
    map
    filter
    retry
    Publisher from
    HTTP reactive
    client
    

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

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

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59. go DEEPER!
    async sub-processes with flatMap
    

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

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

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

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

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66. & much
    more...
    

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67. threading
    contexts
    

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68. Reactor
    is
    agnostic
    

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69. however it
    facilitates switching
    

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70. Schedulers
    

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71. Schedulers
    elastic, parallel, single, timer...
    

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72. publishOn
    switch rest of the flux on a thread
    

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

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

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

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

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

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

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

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80. Testing & Debugging
    in an asynchronous world
    

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81. Testing a Publisher
    StepVerifier
    

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82. Testing a Publisher
    with Virtual Time support
    

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83. Simulate a source
    TestPublisher
    

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84. Debugging Issues
    stacktraces get hard to decipher
    

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85. usually just show
    where Subscription happens
    

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86. 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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87. Find where the Flux
    was instantiated (assembly)
    

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88. Checkpoint()
    or full assembly tracing
    

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89. costly!
    Checkpoint()
    or full assembly tracing
    

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90. 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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91. BACKPRESSURE
    and other beasts
    

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92. Publisher Subscriber
    subscribe
    

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93. Publisher Subscriber
    push data as fast as possible
    

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

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95. Publisher Subscriber
    1 onNext
    

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96. Publisher Subscriber
    request more
    (eg. 2)
    

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97. Publisher Subscriber
    2 onNext
    

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98. Publisher Subscriber
    backpressure
    

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

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100. internal
     optimisations
     

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

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102. micro FUSION
     share internal structures for less allocation
     

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103. lock free operators
     

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104. lock free operators
     and Work Stealing
     cpu 1
     cpu 2
     cpu 3
     cpu 4
     cpu 5
     

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105. Reactor and
     Spring
     

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

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107. NO philosoraptor you don’t
     

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

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110. Java 8
     baseline
     

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111. reactive
     focus
     

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112. new WEB stack
     WebFlux
     

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

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114. functional option
     for Routing
     

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115. Spring Data
     reactive repositories
     

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

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117. Reactor and the Network
     reactor-netty
     

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

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119. Client / Server
     

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120. TCP
     or udp
     

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121. Http
     and WebSockets
     

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122. 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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123. still a bit low level
     

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124. still a bit low level
     

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125. reactor-kafka
     topics as
     Flux
     

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126. reactive API
     over Kafka Producer / Consumer
     

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127. send(Flux)
     into Kafka
     

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128. Flux receive()
     from Kafka
     

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129. (currently in MILESTONE 1)
     

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130. 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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