A lite Rx API for the JVM

With Flux and Mono, Reactor Core 3.0 provides a lite Rx API for Java 8+. Try the Hands-on available at https://github.com/reactor/lite-rx-api-hands-on/.

Transcript

1. Unless otherwise indicated, these slides are © 2013-2015 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
   Reactor Core 3.0
   A lite Rx API for the JVM
   Sébastien Deleuze - Stéphane Maldini
   @sdeleuze - @smaldlini
   

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2. Unless otherwise indicated, these slides are © 2013-2015 Pivotal Software, Inc. and licensed under a

   Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
   Sébastien Deleuze
   • Live in Lyon
   • Remote worker @ Pivotal
   • Spring Framework and Reactor committer
   • Works on Spring Framework 5

   upcoming Reactive support
   • Co-worker @ La Cordée
   • Mix-IT staff member
   • @sdeleuze on Twitter
   2
   

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3. Unless otherwise indicated, these slides are © 2013-2015 Pivotal Software, Inc. and licensed under a

   Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
   Stéphane Maldini
   • Survive in London
   • Social Engineering @
   • Project Reactor lead
   • Reactive Streams & 

   Reactive Streams Commons contributor
   • Works on Spring Framework 5

   upcoming Reactive support
   • @smaldini on Twitter
   3
   +
   

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4. Unless otherwise indicated, these slides are © 2013-2015 Pivotal Software, Inc. and licensed under a

   Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
   Why going reactive?
   • More for scalability and stability than for speed
   • Use cases:
   • Webapp calling remote web services
   • Lot of slow clients
   • Big Data
   • Serve more clients on the same hardware
   • Event based development (web, mobile)
   4
   

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5. Unless otherwise indicated, these slides are © 2013-2015 Pivotal Software, Inc. and licensed under a

   Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
   Reactive, what is it?
   5
   More details on http://fr.slideshare.net/StphaneMaldini/intro-to-reactive-programming-52821416
   • Reactive is used to broadly define event-driven systems
   • Reactive Manifesto defines qualities of reactive systems
   • Reactive programming: moving imperative logic to async, non-
   blocking, functional-style code, in particular when interacting
   with external resources
   

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   For reactive programming, we need tools :
   ☐ Reactive Streams
   ☐ Reactive APIs
   6
   

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   Reactive Streams
   • Reactive Streams is a contract for asynchronous stream
   processing with non-blocking back pressure
   • De facto standard for interop between reactive libraries
   • To be included in Java 9 as java.util.concurrent.Flow
   7
   

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8. Unless otherwise indicated, these slides are © 2013-2015 Pivotal Software, Inc. and licensed under a

   Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
   Reactive Streams principle
   8
   Publisher Subscriber
   Data
   Demand
   • Max(InflightData) <= demand
   • No data sent without demand
   • Demand can be unbounded
   • The recipient controls how much data it will receive
   

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9. Unless otherwise indicated, these slides are © 2013-2015 Pivotal Software, Inc. and licensed under a

   Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
   Reactive Streams is 4 interfaces (+ a TCK)
   9
   public interface Publisher {
   void subscribe(Subscriber super T> s);
   }
   public interface Subscriber {
   void onSubscribe(Subscription s);
   void onNext(T t);
   void onError(Throwable t);
   void onComplete();
   }
   public interface Subscription {
   void request(long n);
   void cancel();
   }
   public interface Processor extends Subscriber, Publisher {
   }
   

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10. Unless otherwise indicated, these slides are © 2013-2015 Pivotal Software, Inc. and licensed under a

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    10
    For reactive programming, we need tools :
    ☑ Reactive Streams
    ☐ Reactive APIs
    

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    • Buffer, merge, concatenate, or apply a wide range 

    of transformations to your data
    • On the JVM:
    • Reactor 3.0 is 4th generation* and based on Reactive Streams
    • RxJava 1.x: 2nd generation* and most used implementation
    • Akka Stream 2.x: Lightbend 3rd generation* Reactive API
    • Also for other languages, for example RxJS, MostJS
    Reactive APIs
    11
    * Based on http://akarnokd.blogspot.fr/2016/03/operator-fusion-part-1.html
    

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    Reactor Core 3.0
    • Built with major contributions from Dávid Karnok (RxJava lead)
    and from some Spring Framework committers
    • Natively based on Reactive Streams, RSC* and Java 8+
    • Strong focus on efficiency
    • Powerful Mono API
    • Ever-improving debugging, logging, testing capabilities
    * ReactiveStreamsCommons is a research effort about reactive flows
    12
    

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    Reactor 3.0 ecosystem
    13
    

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    Flux (0..N elements) with ReactiveX compliant API
    14
    

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    Mono (0..1 element)
    15
    

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    Reactor Web Console
    16
    

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    Type comparaison
    17
    No value Single value Multiple values
    Blocking void T

    Future
    Iterable
    Collection
    Stream
    Non-
    blocking
    CompletableFuture CompletableFuture CompletableFuture>
    Reactive

    Streams
    Publisher Publisher Publisher
    RxJava Completable Single Observable
    Reactor Mono Mono Flux
    

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18. Unless otherwise indicated, these slides are © 2013-2015 Pivotal Software, Inc. and licensed under a

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    https://spring.io/blog/2016/04/19/understanding-reactive-types
    18
    

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    Reactive Spring
    19
    • Spring projects are going reactive
    • Reactor Core is the reactive foundation
    • RxJava adapters provided
    • You will be able to choose your web engine:

    Tomcat, Jetty, Undertow or Netty
    • Most impact on Web and Data support (IO intensive)
    • Spring Reactive experiment
    • Spring Reactive Playground sample application
    

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20. Unless otherwise indicated, these slides are © 2013-2015 Pivotal Software, Inc. and licensed under a

    Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
    Well known Controller example
    20
    @RestController
    public class UserController {
    private BlockingRepository repository;
    @RequestMapping(path = "/save-capitalized", method = RequestMethod.POST)
    public void saveCapitalized(@RequestBody List users) {
    users.forEach(u -> u.setName(u.getName().toUpperCase()));
    repository.save(users);
    }
    }
    public interface BlockingRepository {
    void save(List elements);
    Iterable findAll();
    }
    

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21. Unless otherwise indicated, these slides are © 2013-2015 Pivotal Software, Inc. and licensed under a

    Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
    Controller with Reactive types
    21
    @RestController
    public class UserController {
    private ReactiveRepository repository;
    @RequestMapping(path = "/save-capitalized", method = RequestMethod.POST)
    public Mono saveCapitalized(@RequestBody Flux users) {
    return repository.save(users.map(u -> new User(u.getName().toUpperCase()));
    }
    }
    public interface ReactiveRepository {
    Mono save(Publisher elements);
    Flux findAll();
    }
    

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22. Unless otherwise indicated, these slides are © 2013-2015 Pivotal Software, Inc. and licensed under a

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    Blocking vs Reactive: memory consumption
    22
    Memory consumption
    Time
    Blocking Reactive
    

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23. Unless otherwise indicated, these slides are © 2013-2015 Pivotal Software, Inc. and licensed under a

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    Blocking vs Reactive: streaming updates
    23
    Number of users saved
    in the database
    Time
    Blocking Reactive
    

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    Controller with Reactive return values
    24
    @RestController
    public class UserController {
    private ReactiveRepository repository;
    @RequestMapping(path = "/", method = RequestMethod.GET)
    public Flux findAll() {
    return repository.findAll();
    }
    }
    • Optimized serialization when using Flux instead of List
    • Also perfectly suitable for Server-Sent Events
    

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25. Unless otherwise indicated, these slides are © 2013-2015 Pivotal Software, Inc. and licensed under a

    Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
    Reactive HTTP client with Mono
    25
    import static org.springframework.web.client.reactive.HttpRequestBuilders.*;
    import static org.springframework.web.client.reactive.WebResponseExtractors.*;
    Mono result = webClient
    .perform(get("http://localhost:8080/person")
    .header("X-Test-Header", "testvalue")
    .accept(MediaType.APPLICATION_JSON))
    .extract(body(Person.class));
    

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26. Unless otherwise indicated, these slides are © 2013-2015 Pivotal Software, Inc. and licensed under a

    Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
    Reactive HTTP client with Flux
    26
    import static org.springframework.web.client.reactive.HttpRequestBuilders.*;
    import static org.springframework.web.client.reactive.WebResponseExtractors.*;
    Flux response = webClient
    .perform(get("http://localhost:8080/persons")
    .accept(MediaType.APPLICATION_JSON))
    .extract(bodyStream(Person.class));
    Works for:
    • JSON array [{"foo":"bar"},{"foo":"baz"}]
    • JSON Streaming {"foo":"bar"}{"foo":"baz"}
    • SSE with something like .extract(sseStream(Person.class))
    

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27. Unless otherwise indicated, these slides are © 2013-2015 Pivotal Software, Inc. and licensed under a

    Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
    Perfect fit for Microservices
    27
    Can handle bidirectional stream processing
    

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28. Unless otherwise indicated, these slides are © 2013-2015 Pivotal Software, Inc. and licensed under a

    Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
    Now let’s go to the code!
    28
    https://github.com/reactor/lite-rx-api-hands-on/
    

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