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Unless otherwise indicated, these slides are © 2013-2014 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Reactive Spring JAX 2017 Mark Paluch, Pivotal Software, Inc. @mp911de

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Unless otherwise indicated, these slides are © 2013-2017 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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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ What is Reactive Programming?

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ ! Imperative ! Reactive ! Synchronous ! Blocking ! Non-Blocking ! Asynchronous ! Actors 4 Programming models

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 5 Understanding imperative HttpClient c = …; HttpGet get = new HttpGet("https://google.com"); HttpResponse response = c.execute(get);

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 6 Understanding imperative EntityManager entityManager = …; List users = … entityManager.getTransaction().begin(); for (User user : users) { entityManager.persist(user); } entityManager.getTransaction().commit();

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 7 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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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 8 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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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Use Case: Remote calls with latency 9 Request Data access Remote data service

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Use Case: Remote calls with latency 9 Request Data access Remote data service

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Use Case: Remote calls with latency 9 Request Data access Remote data service I/O Wait

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Use Case: Remote calls with latency 9 Request Data access Remote data service I/O Wait

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Use Case: Remote calls with latency 9 Request Data access Remote data service I/O Wait This one is waiting

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Use Case: Remote calls with latency 9 Request Data access Remote data service I/O Wait This one is waiting

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ ! Makes assumptions over resource usage ! Developers are in charge of resource usage efficiency 10 Imperative programming

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ ! 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 11 Imperative: Web applications

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ ! Reactive is used to describe event-driven systems ! Reactive is used more for scalability and stability than for speed ! Reacts to resource availability 12 What is reactive?

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Use Case: Synchronous fetch model 13

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Use Case: Synchronous fetch model 13 Service App Data store App Service

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Use Case: Serve slow clients 14 Server

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Use Case: Serve slow clients 15 Server

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Use Case: Push message to client 16 Server Message Broker

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ ! Live (continuous) database queries ! UI event handling (Android) ! Big Data ! Real time analytics ! HTTP/2 17 Other use cases

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ ! A form of computer timing control protocol ! Starts processing after receiving a signal ! Completed eventually 18 Asynchronous

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ ! Introduces concurrency ! Does not block the caller • At least in the first place ! Keeps more Threads busy 19 Asynchronous

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ ! Unit of execution • Runnable ! Executor • Thread • ThreadPool 20 Asynchronous: Requirements

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Asynchronous: Future 21 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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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 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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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 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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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 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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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Say „callback“ to a JavaScript developer and he will start crying instantaneously! – Venkat Subramaniam 25

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 26 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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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ ! Available since Java 8 ! Functional composition ! Functional transformation 27 Asynchronous: CompletableFuture

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Asynchronous: CompletableFuture example 28 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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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 29 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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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Understanding the Java Memory Model is hard. Getting concurrency right is harder. 30

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Effects of an async fetch model 31 Request I/O

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Effects of an async fetch model 31 Request I/O

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Effects of an async fetch model 31 Request I/O

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Effects of an async fetch model 31 Request I/O

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Effects of an async fetch model 31 Request I/O Requires synchronization

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Effects of an async fetch model 31 Request I/O Requires synchronization Still waiting, eh?

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Effects of an async fetch model 31 Request I/O Requires synchronization Still waiting, eh?

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ ! Makes assumptions over resource usage ! Need a change • Change programming model 32 Imperative programming

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ We need a different toolset! 33

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ We need a different toolset! 34

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ ! Allows building and composing asynchronous applications ! Reacts to the availability of resources ! Requires a reactive API 35 Reactive programming model

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ ! 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 36 Reactive Streams

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Publisher and Subscriber 37 Subscriber Publisher Subscribe Data

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Publisher and Subscriber 37 Subscriber Publisher Subscribe Data

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Publisher and Subscriber 37 Subscriber Publisher Subscribe Data

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 38 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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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ ! Apply a wide range of operators: map, split, merge, delay RxJava 1 & 2 Project Reactor Akka Streams 39 Reactive libraries

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 40 Reactive APIs on the JVM Reactive API Reactive Streams
 Type Non-Reactive
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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 41 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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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ ! Use Reactor if • using Java 8 ! Use RxJava if • stuck with Java 6 • need checked Exceptions in functions 42 RxJava 2 or Project Reactor

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ ! „Volume knob“ for data emission ! Communicates demand (capacity) of the subscriber to the publisher 43 Back pressure

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ ! Request all the data ! Now 44 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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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Asynchronous fetch model 45

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Asynchronous fetch model 45 Remote App Remote Remote App can’t keep up (Back pressure)

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Asynchronous fetch model 45 Remote App Remote Remote App can’t keep up (Back pressure)

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Publisher and Subscriber 46 Subscriber Publisher Publish as fast as possible

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 47 Publisher

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 47 Publisher I/O thread push

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Back pressure control 48 Subscriber Publisher Demand

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Back pressure control 49 Subscriber Publisher Demand

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Reactive fetch model 50

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Reactive fetch model 50 Data store App

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Reactive fetch model 50 Data store App Data store

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Reactive fetch model 50 Data store App Data store Data store

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Reactive fetch model 50 Data store App Data store Data store Data store App

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Reactive fetch model 50 Data store App Data store Data store Data store App

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Introduction to Project Reactor

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ How do you achieve asynchronous, non-blocking processing? Without losing your mind? 52

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 53

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 54

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 55 List Iterator Future Future>

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 55 List Iterator Future Future> .get() for-each .hasNext()

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 55 List Iterator Future Future> .get() for-each .hasNext() Request thread pulls

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 56 Publisher

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 56 Publisher Thread pushes data

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 57 Iterable Iterator Publisher Subscriber

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 57 Iterable Iterator Publisher Subscriber vs.

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 58 Subscriber Publisher feedback push events produces consumes Relation between Publisher and Subscriber

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 59 Subscriber Publisher feedback push events produces consumes interfaces from Reactive Streams spec Relation between Publisher and Subscriber

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 60 Subscriber Publisher feedback 0..N elements + 0..1 (complete | error) produces consumes Signals

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 61 Subscriber Publisher push events produces consumes Demand (Back pressure control) Back pressure

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 62 Subscriber Publisher push events produces consumes can I have an API though?

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 63 Subscriber Publisher push events produces consumes

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 64 Project Reactor 3

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ ! 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 114 Reactive Spring portfolio

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Unless otherwise indicated, these slides are © 2013-2017 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 115 What is WebFlux?

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Unless otherwise indicated, these slides are © 2013-2017 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 120 Spring Web MVC

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Unless otherwise indicated, these slides are © 2013-2017 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 124 Todays’ data access

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ ! Project Reactor 3.0 ! Spring Framework 5.0 ! Spring Data 2.0 ! A reactive (asynchronous, ideally non-blocking) driver ! Optional: Spring Boot 2.0 125 Requirements for Reactive Spring Data

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Unless otherwise indicated, these slides are © 2013-2017 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 126 Reactive Spring Data

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Unless otherwise indicated, these slides are © 2013-2017 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 144 What does it take to go reactive?

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Unless otherwise indicated, these slides are © 2013-2017 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 145 Existing applications

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Unless otherwise indicated, these slides are © 2013-2017 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 146 Reactive language

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Unless otherwise indicated, these slides are © 2013-2017 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 147 Reactive Streams

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Unless otherwise indicated, these slides are © 2013-2017 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 148 Reactive composition library

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 149 … 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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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 150 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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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 151 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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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 152 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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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Questions? Mark Paluch • @mp911de

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Unless otherwise indicated, these slides are © 2013-2017 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 154 @mp911de