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
   

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

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3. WHY?
   

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4. WHY?
   because blocking is evil
   

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

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

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

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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
   processin
   g
   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. vs
    Iterable
    -
    Iterator
    Publisher
    -
    Subscriber
    

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18. Data in Flux
    

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19. Publisher Subscriber
    push events
    produces consumes
    feedback
    

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

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

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

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23. Publisher Subscriber
    push events
    produces consumes
    feedback
    backpressure
    

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

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25. Publisher Subscriber
    push events
    produces consumes
    feedback
    

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26. Reactor 3
    types and operators
    

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27. Flux
    for 0..N elements
    

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29. Mono
    for at most 1 element
    

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31. Reactive Streams
    all the way
    

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32. focus on Java 8
    

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33. focus on Java 8
    Duration, CompletableFuture, Streams
    

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

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

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

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

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

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

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40. “elements of functional programming”
    

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41. threading
    contexts
    

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42. Reactor is
    agnostic
    

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43. however it
    facilitates switching
    

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44. Schedulers
    

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45. Schedulers
    elastic, parallel, single, timer...
    

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46. publishOn
    switch rest of the flux on a thread
    

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

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48. Flux/Mono
    generator
    operator
    subscribeOn
    operator
    publishOn
    operator
    operator
    Subscriber
    Sub
    Sub
    Sub
    Sub
    Sub
    Sub
    

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

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50. Flux/Mono
    generator
    operator
    subscribeOn
    operator
    publishOn
    operator
    operator
    Subscriber
    Sub
    Sub
    Sub
    Sub
    Sub
    Sub
    

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51. Flux/Mono
    generator
    operator
    subscribeOn
    operator
    publishOn
    operator
    operator
    Subscriber
    Sub
    Sub
    Sub
    Sub
    Sub
    Sub
    

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52. Flux/Mono
    generator
    operator
    subscribeOn
    operator
    publishOn
    operator
    operator
    Subscriber
    Sub
    Sub
    Sub
    Sub
    Sub
    Sub
    

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53. Flux/Mono
    generator
    operator
    subscribeOn
    operator
    publishOn
    operator
    operator
    Subscriber
    Sub
    Sub
    Sub
    Sub
    Sub
    Sub
    

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54. CODING
    TIME!
    

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56. Bonus Slides
    operator step-by-step examples, backpressure
    

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57. map, filter, buffer
    

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58. Flux.range
    Subscriber
    map
    filter
    buffer
    

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

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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
    Subscriber
    map
    filter
    buffer
    

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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. retry
    

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72. 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
    

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

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76. Trickier: flatMap
    async sub-processes
    

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

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83. & much
    more...
    

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84. backpressure
    the "volume control"
    

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85. Publisher Subscriber
    subscribe
    

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86. Publisher Subscriber
    push data as fast as possible
    

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

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88. Publisher Subscriber
    1 onNext
    

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89. Publisher Subscriber
    request more
    (eg. 2)
    

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90. Publisher Subscriber
    2 onNext
    

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91. Publisher Subscriber
    backpressure
    

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

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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.
    

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