Reactive Spring Workshop

Code: https://github.com/mp911de/reactive-spring

Transcript

1. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
   
   Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
   Reactive Spring Workshop
   Mark Paluch, Pivotal Software, Inc.
   @mp911de
   

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2. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
   
   Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
   @mp911de
   github.com/mp911de
   paluch.biz
   Mark Paluch
   

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3. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
   
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   Programm
   ! 10:00 Begrüßung
   ! 10:15–11:30 Was ist Reaktive Programmierung?
   ! 11:30-13:00 Einführung in Project Reactor
   ! 13:00-14:00 Mittagspause
   ! 14:00-15:00 Spring WebFlux
   ! 15:00–15:30 Pause
   ! 15:30-16:30 Reactive Spring Data
   !3
   

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4. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
   
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   What is Reactive
   Programming?
   

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   ! Imperative
   ! Reactive
   ! Synchronous
   ! Blocking
   ! Non-Blocking
   ! Asynchronous
   ! Actors
   !5
   Programming models
   

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   !6
   Understanding imperative
   HttpClient c = …;
   HttpGet get = new HttpGet("https://google.com");
   HttpResponse response = c.execute(get);
   

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   !7
   Understanding imperative
   EntityManager entityManager = …;
   List users = …
   entityManager.getTransaction().begin();
   for (User user : users) {
   entityManager.persist(user);
   }
   entityManager.getTransaction().commit();
   

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   !8
   Understanding imperative
   public void saveUsers() {
   EntityManager entityManager = …;
   List users = …
   entityManager.getTransaction().begin();
   for (User user : users) {
   entityManager.persist(user);
   }
   entityManager.getTransaction().commit();
   }
   

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   !9
   Understanding imperative
   HttpClient c = …;
   for (int i = 0; i < 10; i++) {
   HttpGet get = new HttpGet("https://google.com");
   HttpResponse response = c.execute(get);
   // …
   }
   

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10. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
    
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    Use Case: Remote calls with latency
    !10
    Request Data access
    Remote data
    service
    I/O Wait
    
    This one is
    waiting
    

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    ! Makes assumptions over resource usage
    ! Developers are in charge of resource usage efficiency
    !11
    Imperative programming
    

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    ! Container calls code on a Thread
    ! Call continues until all work is done
    ! Thread is occupied
    ! Thread is released at the end of work
    • Latencies affect duration in which Thread is occupied
    !12
    Imperative: Web applications
    

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    Use Case: Synchronous fetch model
    !13
    Service
    App
    Data store
    App
    Service
    

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    ! Reactive is used to describe event-driven systems
    ! Reactive is used more for scalability and stability than
    for speed
    ! Reacts to resource availability
    !14
    What is reactive?
    

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    Use Case: Serve slow clients
    !15
    Server
    

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    Use Case: Serve slow clients
    !16
    Server
    

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    Use Case: Push message to client
    !17
    Server
    Message Broker
    

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    ! Live (continuous) database queries
    ! UI event handling (Android)
    ! Big Data
    ! Real time analytics
    ! HTTP/2
    !18
    Other use cases
    

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    ! A form of computer timing control protocol
    ! Starts processing after receiving a signal
    ! Completed eventually
    !19
    Asynchronous
    

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    ! Introduces concurrency
    ! Does not block the caller
    • At least in the first place
    ! Keeps more Threads busy
    !20
    Asynchronous
    

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    ! Unit of execution
    • Runnable
    ! Executor
    • Thread
    • ThreadPool
    !21
    Asynchronous: Requirements
    

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    Asynchronous: Future
    !22
    AsyncRestTemplate asyncRestTemplate = …
    AsyncCassandraTemplate asyncCassandra = …
    SettableListenableFuture future = new SettableListenableFuture<>();
    asyncRestTemplate.getForEntity("https://slow-service.com", String.class)
    .addCallback(response -> {
    Page page = new Page();
    page.setId(…);
    page.setContent(response.getBody());
    ListenableFuture insertFuture = asyncCassandra.insert(page);
    insertFuture.addCallback(savedPage -> future.set("OK"),
    failure -> future.setException(failure));
    }, failure -> failure -> future.setException(failure));
    return future;
    

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    Asynchronous: Future
    !23
    AsyncRestTemplate asyncRestTemplate = …
    AsyncCassandraTemplate asyncCassandra = …
    SettableListenableFuture future = new SettableListenableFuture<>();
    asyncRestTemplate.getForEntity("https://slow-service.com", String.class)
    .addCallback(response -> {
    Page page = new Page();
    page.setId(…);
    page.setContent(response.getBody());
    ListenableFuture insertFuture = asyncCassandra.insert(page);
    insertFuture.addCallback(savedPage -> future.set("OK"),
    failure -> future.setException(failure));
    }, failure -> failure -> future.setException(failure));
    return future;
    

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    Asynchronous: Future
    !24
    AsyncRestTemplate asyncRestTemplate = …
    AsyncCassandraTemplate asyncCassandra = …
    SettableListenableFuture future = new SettableListenableFuture<>();
    asyncRestTemplate.getForEntity("https://slow-service.com", String.class)
    .addCallback(response -> {
    Page page = new Page();
    page.setId(…);
    page.setContent(response.getBody());
    ListenableFuture insertFuture = asyncCassandra.insert(page);
    insertFuture.addCallback(savedPage -> future.set("OK"),
    failure -> future.setException(failure));
    }, failure -> failure -> future.setException(failure));
    return future;
    

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    Asynchronous: Future
    !25
    AsyncRestTemplate asyncRestTemplate = …
    AsyncCassandraTemplate asyncCassandra = …
    SettableListenableFuture future = new SettableListenableFuture<>();
    asyncRestTemplate.getForEntity("https://slow-service.com", String.class)
    .addCallback(response -> {
    Page page = new Page();
    page.setId(…);
    page.setContent(response.getBody());
    ListenableFuture insertFuture = asyncCassandra.insert(page);
    insertFuture.addCallback(savedPage -> future.set("OK"),
    failure -> future.setException(failure));
    }, failure -> failure -> future.setException(failure));
    return future;
    

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    Say „callback“ to a JavaScript
    developer and he will start crying
    instantaneously!
    – Venkat Subramaniam
    !26
    

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    !27
    Using Java types
    Non-
    Blocking
    Streaming Pattern
    Future x Pull
    CompletableFuture x Push
    Stream x Pull
    Iterator x Pull
    Input/OutputStream x Pull
    

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    ! Available since Java 8
    ! Functional composition
    ! Functional transformation
    !28
    Asynchronous: CompletableFuture
    

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    Asynchronous: CompletableFuture example
    !29
    CompletableFuture> future = …
    future.thenCompose(response -> {
    Page page = new Page();
    page.setId(…);
    page.setContent(response.getBody());
    return asyncCassandra.insert(page);
    }).thenApply(Page::getId);
    

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    !30
    Concurrency effects
    public static class Test extends Thread {
    boolean keepRunning = true;
    public void run() {
    long count = 0;
    while (keepRunning) {
    count++;
    }
    System.out.println("Thread terminated after cycles: " + count);
    }
    }
    public static void main(String[] args) throws InterruptedException {
    Test t = new Test();
    t.start();
    System.out.println("Started");
    Thread.sleep(1000);
    t.keepRunning = false;
    System.out.println("keepRunning set to false.");
    }
    

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    Understanding the Java Memory Model is hard.
    Getting concurrency right is harder.
    !31
    

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    Effects of an async fetch model
    !32
    Request I/O
    Requires
    synchronization
    Still waiting, eh?
    
    
    
    

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    ! Makes assumptions over resource usage
    ! Need a change
    • Change programming model
    !33
    Imperative programming
    

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    We need a different toolset!
    !34
    

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    We need a different toolset!
    !35
    

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    ! Allows building and composing asynchronous applications
    ! Reacts to the availability of resources
    ! Requires a reactive API
    !36
    Reactive programming model
    

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    ! Collaborative initiative to provide a standard for
    asynchronous stream processing with non-blocking back
    pressure.
    ! Co-designed by Twitter, Lightbend, Pivotal, Netflix and many
    others
    ! De-facto interop standard
    ! Java 9: Flow API
    !37
    Reactive Streams
    

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    Publisher and Subscriber
    !38
    Subscriber
    Publisher
    Subscribe
    Data
    

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    !39
    Distributions
    org.reactivestreams:reactive-streams
    • Publisher
    • Subscriber
    • Subscription
    • Processor
    • Flow.Publisher
    • Flow.Subscriber
    • Flow.Subscription
    • Flow.Processor
    Part of Java 9 in java.util.concurrent
    

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    ! Apply a wide range of operators: map, split, merge, delay
    RxJava 1 2
    Project Reactor
    Akka Streams
    !40
    Reactive libraries
    

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    !41
    Reactive APIs on the JVM
    Reactive API
    Reactive Streams

    Type
    Non-Reactive

    Streams Type
    RxJava 1
    Observable

    Single

    Completable
    RxJava 2 Flowable
    Observable

    Single

    Maybe,Completable
    Akka Streams 2
    Source

    Sink

    Flow
    Project Reactor
    Mono

    Flux
    

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    !42
    Reactive APIs on the JVM: Generations
    Reactive API Generation Support
    RxJava 1 2nd Limited back pressure
    RxJava 2 4th
    Reactive Streams +
    operator fusion
    Akka Streams 2 3rd
    Reactive Streams +
    actor fusion
    Project Reactor 4th
    Reactive Streams +
    operator fusion
    

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    ! Use Reactor if
    • using Java 8
    ! Use RxJava if
    • stuck with Java 6
    • need checked Exceptions in functions
    !43
    RxJava 2 or Project Reactor
    

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    ! „Volume knob“ for data emission
    ! Communicates demand (capacity) of the subscriber to the
    publisher
    !44
    Back pressure
    

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    ! Request all the data
    ! Now
    !45
    Asynchronous fetch model
    AsyncHttpClient c = …;
    for (int i = 0; i < 10; i++) {
    HttpGet get = new HttpGet("https://google.com");
    Future response = c.execute(get);
    // …
    }
    

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    Asynchronous fetch model
    !46
    Remote
    App
    Remote Remote
    App can’t keep up
    (Back pressure)
    
    

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    Publisher and Subscriber
    !47
    Subscriber
    Publisher
    Publish as fast as possible
    

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    !48
    Publisher
    I/O thread
    push
    

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    Back pressure control
    !49
    Subscriber
    Publisher
    Demand
    

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    Back pressure control
    !50
    Subscriber
    Publisher
    Demand
    

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    Reactive fetch model
    !51
    Data store
    App
    Data store Data store Data store
    App
    
    

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    Zeit für Fragen
    11:30-13:00 Einführung in Project Reactor
    

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    Introduction to
    Project Reactor
    

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    How do you achieve asynchronous, non-blocking
    processing?
    Without losing your mind?
    !54
    

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    !55
    

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    !56
    

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    !57
    List
    Iterator
    Future
    Future>
    .get()
    for-each .hasNext()
    Request thread pulls
    

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    !58
    Publisher
    Thread
    pushes data
    

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    !59
    Iterable
    Iterator
    Publisher
    Subscriber
    vs.
    

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    !60
    Subscriber
    Publisher
    feedback
    push events
    produces consumes
    Relation between Publisher and Subscriber
    

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    !61
    Subscriber
    Publisher
    feedback
    push events
    produces consumes
    interfaces from Reactive Streams spec
    Relation between Publisher and Subscriber
    

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    !62
    Subscriber
    Publisher
    feedback
    0..N elements
    +
    0..1 (complete | error)
    produces consumes
    Signals
    

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    !63
    Subscriber
    Publisher
    push events
    produces consumes
    Demand (Back pressure control)
    Back pressure
    

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    !64
    Subscriber
    Publisher
    push events
    produces consumes
    can I have an
    API though?
    

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    !65
    Subscriber
    Publisher
    push events
    produces consumes
    

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    !66
    Project Reactor 3
    

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    Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
    ! Composing asynchronous & event-based sequences, using
    non-blocking operators
    ! Without sacrifice
    • No callback hell
    • No Futures
    ! End to end Reactive Streams
    !67
    Project Reactor
    

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68. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
    
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    ! Duration
    ! CompletableFuture
    ! Stream
    !68
    Focus on Java 8
    

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69. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
    
    Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
    Project Reactor Types
    !69
    Mono
    Flux
    0..1..Error
    0..N..Error
    

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70. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
    
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    !70
    This is the timeline of the
    Flux. Time flows from left
    to right.
    These are items emitted by
    the Flux.
    This vertical line indicates that the Flux
    has completed successfully.
    These dotted lines and this box
    indicate that a transformation is being
    applied to the Flux. The text inside the
    box shows the nature of the
    transformation.
    If for some reason the Flux terminates
    abnormally, with an error, the vertical line is
    replaced by an X.
    This Flux is the result
    of the transformation.
    operator
    1 2 3 4 5 6
    1 2 3
    Explaining reactive operations
    

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71. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
    
    Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
    Explaining reactive operations
    !71
    Transformed
    Completion signal
    Error signal
    Emitted element
    Time
    

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72. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
    
    Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
    Flux
    !72
    These are items emitted by
    the Flux.
    operator
    1 2 3 4 5 6
    1 2 3
    

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73. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
    
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    Mono
    !73
    This is the eventual item
    emitted by the Mono.
    operator
    1
    1
    

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74. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
    
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    !74
    Operators
    an Rx-inspired API
    with a vocabulary of operators similar to RxJava...
    

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75. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
    
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    !75
    Operators
    an Rx-inspired API
    ...but not exactly the same
    

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76. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
    
    Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
    !76
    Flux/Mono
    generator
    operator
    operator
    operator
    nothing happens
    until you subscribe
    

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77. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
    
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    !77
    Flux/Mono
    generator
    Subscriber
    operator
    operator
    operator
    nothing happens
    until you subscribe
    

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78. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
    
    Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
    Flux/Mono
    generator
    Subscriber
    operator
    operator
    operator
    Sub
    Sub
    Sub
    per Subscription
    state
    

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79. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
    
    Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
    data
    flows
    Flux/Mono
    generator
    Subscriber
    operator
    operator
    operator
    Sub
    Sub
    Sub
    

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80. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
    
    Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
    ! Reactor is agnostic
    ! Facilitates switching
    ! Schedulers
    !80
    Threading (contexts)
    

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81. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
    
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    ! single: Single-Threaded scheduler
    ! elastic: Grows (unbounded) as needed
    • used for I/O offloading
    ! parallel: Fixed-sized at number of CPU cores
    • Event-Loop
    ! timer: Timed tasks
    !81
    Schedulers
    

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82. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
    
    Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
    ! publishOn
    • switch emission of the Publisher on a thread
    ! subscribeOn
    • make the subscription and request happen on a particular
    thread
    !82
    Context switching
    

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83. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
    
    Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
    !83
    Flux/Mono
    generator
    operator
    subscribeOn
    operator
    publishOn
    operator
    operator
    Subscriber
    Sub
    Sub
    Sub
    Sub
    Sub
    Sub
    

    View Slide

84. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
    
    Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
    !84
    Flux/Mono
    generator
    operator
    subscribe
    On
    operator
    publish
    On
    operator
    operator
    Subscriber
    Sub
    Sub
    Sub
    Sub
    Sub
    Sub
    

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85. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
    
    Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
    !85
    Flux/Mono
    generator
    operator
    subscribeOn
    operator
    publishOn
    operator
    operator
    Subscriber
    Sub
    Sub
    Sub
    Sub
    Sub
    Sub
    

    View Slide

86. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
    
    Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
    !86
    Flux/Mono
    generator
    operator
    subscribeOn
    operator
    publishOn
    operator
    operator
    Subscriber
    Sub
    Sub
    Sub
    Sub
    Sub
    Sub
    

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87. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
    
    Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
    !87
    Flux/Mono
    generator
    operator
    subscribeOn
    operator
    publishOn
    operator
    operator
    Subscriber
    Sub
    Sub
    Sub
    Sub
    Sub
    Sub
    

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88. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
    
    Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
    !88
    Flux/Mono
    generator
    operator
    subscribeOn
    operator
    publishOn
    operator
    operator
    Subscriber
    Sub
    Sub
    Sub
    Sub
    Sub
    Sub
    

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89. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
    
    Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
    Operator time!
    map, filter, buffer
    !89
    

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90. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
    
    Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
    !90
    Flux.range
    Subscriber
    map
    filter
    buffer
    

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91. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
    
    Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
    !91
    

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92. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
    
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    !92
    

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93. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
    
    Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
    !93
    

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94. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
    
    Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
    !94
    Flux.range
    Subscriber
    map
    filter
    buffer
    

    View Slide

95. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
    
    Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
    !95
    Flux.range
    Subscriber
    map
    filter
    buffer
    

    View Slide

96. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
    
    Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
    !96
    Flux.range
    Subscriber
    map
    filter
    buffer
    

    View Slide

97. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
    
    Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
    !97
    Flux.range
    Subscriber
    map
    filter
    buffer
    

    View Slide

98. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
    
    Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
    !98
    Flux.range
    Subscriber
    map
    filter
    buffer
    

    View Slide

99. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
    
    Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
    !99
    Flux.range
    Subscriber
    map
    filter
    buffer
    

    View Slide

100. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
     
     Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
     !100
     Flux.range
     Subscriber
     map
     filter
     buffer
     

     View Slide

101. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
     
     Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
     !101
     Flux.range(5, 3)
     .map(i -> i + 3)
     .filter(i -> i % 2 == 0)
     .buffer(3)
     

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102. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
     
     Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
     !102
     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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103. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
     
     Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
     Operator time²!
     flatMap all the things
     !103
     

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104. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
     
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     ! Asynchronous sub-process
     ! Map to 0, 1 or N elements
     !104
     flatMap operator
     

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105. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
     
     Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
     !105
     

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106. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
     
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     !106
     

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107. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
     
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     !107
     

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108. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
     
     Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
     !108
     flatMap(user -> tweetStream(user))
     

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109. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
     
     Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
     !109
     flatMap(user -> tweetStream(user))
     

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110. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
     
     Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
     !110
     flatMap(user -> tweetStream(user))
     

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111. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
     
     Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
     !111
     flatMap(user -> tweetStream(user))
     

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112. Unless otherwise indicated, these slides are 

     © 2013-2018 Pivotal Software, Inc. and licensed under a
     Creative Commons Attribution-NonCommercial
     license: http://creativecommons.org/licenses/by-nc/3.0/
     Coding Time!
     

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113. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
     
     Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
     Zeit für Fragen
     

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114. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
     
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     Spring WebFlux
     

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115. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
     
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     ! It’s all about efficient resource usage
     ! Turn around the idea of imperative programming
     ! React to the availability of resources
     !115
     What is Reactive Spring
     

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116. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
     
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     Scaling
     !116
     
     
     
     
     
     
     
     

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117. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
     
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     ! Spring WebFlux – Reactive web applications
     ! Spring Data – Reactive data store support
     ! Spring Cloud Stream – Message-driven microservices
     ! Spring Boot – Reactive auto configuration
     ! Spring Security – Security for reactive web applications
     ! Spring Cloud Gateway – API Gateway
     !117
     Reactive Spring portfolio
     

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118. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
     
     Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
     ! Spring’s reactive web framework
     ! End to end non-blocking and asynchronous execution
     !118
     What is WebFlux?
     

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119. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
     
     Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
     ! Project Reactor 3.1
     ! Spring Framework 5.0
     ! Optional: Spring Boot 2.0
     !119
     Requirements
     

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120. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
     
     Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
     !120
     

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121. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
     
     Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
     !121
     

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122. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
     
     Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
     ! Servlet API is thread-bound
     ! Servlet API has no native HTTP/2 support (yet)
     ! No notion of back pressure
     ! SSE API’s (Server-sent events) are vendor-specific
     !122
     

     View Slide

123. Unless otherwise indicated, these slides are 

     © 2013-2018 Pivotal Software, Inc. and licensed under a
     Creative Commons Attribution-NonCommercial
     license: http://creativecommons.org/licenses/by-nc/3.0/
     Coding Time!
     

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124. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
     
     Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
     ! Allows usage of Reactive types
     ! Improves asynchronous usage (DeferredResult)
     ! Improves SSE streaming usage (ResponseBodyEmitter)
     ! Everything else is blocking
     !124
     Spring Web MVC
     

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125. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
     
     Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
     Zeit für Fragen
     15:00–15:30 Pause
     15:30-16:30 Reactive Spring Data
     

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126. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
     
     Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
     Reactive Spring Data
     

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127. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
     
     Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
     Accessing data today
     !127
     Request Data access
     Remote data
     service
     I/O Wait
     This one is
     waiting
     

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128. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
     
     Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
     Accessing data today
     !128
     Request Data access
     Remote data
     service
     Multiple
     calls
     Bulk fetch
     
     

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129. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
     
     Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
     ! Keep resources busy
     ! Connection contention
     ! Usually synchronous/blocking
     ! Multiple requests
     ! Asynchronous isn’t always a good answer
     !129
     Todays’ data access
     

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130. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
     
     Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
     ! Project Reactor 3.1
     ! Spring Framework 5.0
     ! Spring Data 2.0
     ! A reactive (asynchronous, ideally non-blocking) driver
     ! Optional: Spring Boot 2.0
     !130
     Requirements for Reactive Spring Data
     

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131. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
     
     Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
     ! Reactive Template API
     ! Reactive Repository support
     ! Reduced feature set
     !131
     Reactive Spring Data
     

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132. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
     
     Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
     ! MongoDB
     ! Apache Cassandra
     ! Redis
     ! Couchbase
     !132
     Reactive Spring Data modules
     

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133. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
     
     Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
     ! JDBC is a blocking API
     ! JPA is a blocking API
     ! Sorry, no reactive JPA support so far
     ! …but
     !133
     What about JPA
     

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134. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
     
     Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
     ! Efforts from Oracle
     • ADBA
     ! Efforts from Pivotal
     • R2DBC
     ! Third-party
     • RxJava2 JDBC
     • Vert.x drivers
     !134
     Reactive Relational Database Access
     

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135. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
     
     Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
     ! Not a priority but feasible
     • Neo4j
     • Solr
     • ElasticSearch
     !135
     Future reactive Spring Data modules
     

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136. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
     
     Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
     ! Non-blocking I/O
     ! Threading-infrastructure
     ! Back pressure
     ! Integration with reactive libraries
     !136
     Why reactive drivers?
     

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137. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
     
     Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
     Reactive fetch model
     !137
     Data store
     App
     Data store Data store Data store
     App
     
     

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138. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
     
     Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
     !138
     Imperative Template API
     T insert(T objectToSave)
     void insertAll(Collection objects)
     

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139. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
     
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     !139
     Reactive Template API
     Mono insert(T objectToSave)
     Mono insert(Mono objectToSave)
     

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140. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
     
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     !140
     Reactive Repository API
     public interface ReactivePersonRepository extends
     ReactiveCrudRepository {

     

     Flux findByLastname(String lastname);

     

     @Query("{ 'firstname': ?0 }")

     Mono customQuery(String firstname);
     Flux findByLastname(Mono lastname);
     }
     

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141. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
     
     Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
     !141
     Reactive Repository API
     public interface ReactivePersonRepository extends
     ReactiveCrudRepository {

     

     Flux findByLastname(String lastname);

     

     @Query("{ 'firstname': ?0 }")

     Mono customQuery(String firstname);
     Flux findByLastname(Mono lastname);
     }
     

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142. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
     
     Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
     !142
     Reactive Repository API
     public interface ReactivePersonRepository extends
     ReactiveCrudRepository {

     

     Flux findByLastname(String lastname);

     

     @Query("{ 'firstname': ?0 }")

     Mono customQuery(String firstname);
     Flux findByLastname(Mono lastname);
     }
     

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143. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
     
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     !143
     Reactive Repository API
     public interface ReactivePersonRepository extends
     ReactiveCrudRepository {

     

     Flux findByLastname(String lastname);

     

     @Query("{ 'firstname': ?0 }")

     Mono customQuery(String firstname);
     Flux findByLastname(Mono lastname);
     }
     

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144. Unless otherwise indicated, these slides are 

     © 2013-2018 Pivotal Software, Inc. and licensed under a
     Creative Commons Attribution-NonCommercial
     license: http://creativecommons.org/licenses/by-nc/3.0/
     Coding Time!
     

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145. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
     
     Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
     ! Blocking driver
     ! Reactive driver
     ! Requires both drivers and two connections
     ! Collection operations (CRUD, Geo-commands)
     ! Aggregation streaming
     ! No GridFS, MapReduce, Grouping support in Spring Data
     !145
     Reactive MongoDB
     

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146. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
     
     Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
     ! Asynchronous driver (adoption layer)
     ! Feature parity
     ! Optional: Asynchronous Template API with ListenableFuture
     !146
     Reactive Apache Cassandra
     

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147. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
     
     Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
     ! Reactive driver (used for blocking operations as well)
     ! Reactive Template API
     ! Planned: Reactive Pub/Sub
     ! No Reactive Repository support
     !147
     Reactive Redis
     

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148. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
     
     Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
     ! Reactive driver (used for blocking operations as well)
     ! Reactive Template API
     ! Reactive Repository support
     !148
     Reactive Couchbase
     

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149. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
     
     Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
     Going Reactive
     

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150. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
     
     Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
     ! Change your mindset
     ! Non-blocking
     • I/O
     • Computation
     ! Consider if reactive is benefit or burden
     !150
     What does it take to go reactive?
     

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151. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
     
     Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
     ! Carefully consider whether it makes sense
     ! Functional-reactive programming is a good answer for a
     certain class of problems
     ! Can improve code
     ! Can clutter code
     !151
     Existing applications
     

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152. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
     
     Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
     ! Get familiar with the vocabulary
     • Asynchronous
     • non-blocking
     • back pressure
     • reactive
     • reactive extensions
     • streams operators
     !152
     Reactive language
     

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153. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
     
     Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
     ! Don’t implment Reactive Streams interfaces yourself
     • Unless you’re trying the RS TCK to pass
     ! Reactive Streams is just the contract
     • Use a reactive composition library
     ! Nothing happens until subscription
     !153
     Reactive Streams
     

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154. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
     
     Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
     ! Carefully select your tools
     • API
     • Drivers
     ! Tooling is important
     ! Define code styles
     ! Learn reading the stack trace
     !154
     Reactive composition library
     

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155. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
     
     Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
     !155
     …
     at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:926)
     at io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:134)
     at io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:644)
     at io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:579)
     at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:496)
     at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:458)
     at io.netty.util.concurrent.SingleThreadEventExecutor$5.run(SingleThreadEventExecutor.java:858)
     at io.netty.util.concurrent.DefaultThreadFactory$DefaultRunnableDecorator.run(DefaultThreadFactory
     at java.lang.Thread.run(Thread.java:745)
     

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156. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
     
     Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
     !156
     java.lang.NullPointerException: The mapper returned a null value.
     at java.util.Objects.requireNonNull(Objects.java:228)
     at reactor.core.publisher.FluxMapFuseable$MapFuseableSubscriber.onNext(FluxMapFuseable.java
     at reactor.core.publisher.FluxOnAssembly$OnAssemblySubscriber.onNext(FluxOnAssembly.java:37
     at reactor.core.publisher.FluxMapFuseable$MapFuseableSubscriber.onNext(FluxMapFuseable.java
     at reactor.core.publisher.FluxOnAssembly$OnAssemblySubscriber.onNext(FluxOnAssembly.java:37
     at reactor.core.publisher.MonoNext$NextSubscriber.onNext(MonoNext.java:76)
     at reactor.core.publisher.FluxOnAssembly$OnAssemblySubscriber.onNext(FluxOnAssembly.java:37
     at reactor.core.publisher.FluxOnErrorResume$ResumeSubscriber.onNext(FluxOnErrorResume.java:
     at reactor.core.publisher.FluxOnAssembly$OnAssemblySubscriber.onNext(FluxOnAssembly.java:37
     at reactor.core.publisher.FluxOnAssembly$OnAssemblySubscriber.onNext(FluxOnAssembly.java:37
     at reactor.core.publisher.FluxFlatMap$FlatMapMain.innerNext(FluxFlatMap.java:778)
     

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157. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
     
     Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
     !157
     Assembly trace from producer [reactor.core.publisher.MonoMapFuseable] :
     reactor.core.publisher.Mono.map(Mono.java:2126)
     org.springframework.data.redis.core.DefaultReactiveValueOperations.lambda$get$12(DefaultRea
     org.springframework.data.redis.core.DefaultReactiveValueOperations.lambda$createMono$23(Def
     org.springframework.data.redis.core.ReactiveRedisTemplate.doInConnection(ReactiveRedisTempl
     org.springframework.data.redis.core.ReactiveRedisTemplate.lambda$createMono$1(ReactiveRedis
     reactor.core.publisher.MonoDefer.subscribe(MonoDefer.java:45)
     reactor.core.publisher.MonoSwitchIfEmpty.subscribe(MonoSwitchIfEmpty.java:44)
     reactor.core.publisher.Mono.block(Mono.java:1263)
     workshop.CachingController.getOrCreate(CachingController.java:44)
     org.springframework.web.reactive.result.method.InvocableHandlerMethod.doInvoke(InvocableHan
     org.springframework.web.reactive.result.method.InvocableHandlerMethod.lambda$invoke$0(Invoc
     

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158. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
     
     Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
     !158
     Error has been observed by the following operator(s):
     |_ Mono.map(DefaultReactiveValueOperations.java:157)
     |_ Flux.from(ReactiveRedisTemplate.java:296)
     |_ Flux.doOnSignal(ReactiveRedisTemplate.java:296)
     |_ Mono.from(ReactiveRedisTemplate.java:272)
     |_ Mono.defer(ReactiveRedisTemplate.java:272)
     |_ Mono.switchIfEmpty(CachingController.java:44)
     |_ Mono.error(InvocableHandlerMethod.java:127)
     |_ Mono.flatMap(InvocableHandlerMethod.java:116)
     |_ Mono.doOnSignal(RequestMappingHandlerAdapter.java:191)
     |_ Mono.error(RequestMappingHandlerAdapter.java:215)
     |_ Mono.onErrorResume(RequestMappingHandlerAdapter.java:192)
     |_ Mono.defer(RequestMappingHandlerAdapter.java:189)
     |_ Mono.then(RequestMappingHandlerAdapter.java:189)
     |_ Mono.flatMap(DispatcherHandler.java:129)
     |_ Mono.flatMap(DispatcherHandler.java:130)
     |_ Mono.error(ResponseStatusExceptionHandler.java:47)
     |_ Mono.onErrorResume(ExceptionHandlingWebHandler.java:67)
     

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159. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
     
     Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
     Zeit für Fragen
     Mark Paluch • @mp911de
     

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160. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
     
     Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
     Resources
     ! Code - Repository @ Github
     ! Reactor Rx Lite API – Repository @ Github
     ! Spring Data Examples – Repository @ Github
     ! Spring projects release calendar – Google Calendar
     !160
     @mp911de
     

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161. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
     
     Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
     Backup
     !161
     

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162. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a
     
     Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
     Reactive Execution Model
     !162
     Request Data access
     Reactive
     remote data
     service
     That’s not
     the data you’re
     looking for
     Remote data
     service
     Stream
     Demand
     Dispatcher
     

     View Slide