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Reactor 3. Reactive Foundation for Java 8 and Spring

Stephane Maldini @smaldini

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Reactor Core provides for a minimalist set of Reactive Streams ready

generators and transformers

2

WHY ?

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DIY Reactive Streams

Publisher<User> rickSanchez = userRepository.findUser(“rick”);

Might produce 0, 1 or N Users ! Produce User when ready

Callback for start, result, error or complete

rickSanchez.subscribe(new Subscriber<User>(){ … });

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DIY Reactive Streams

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Can I have an API ?

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3 years to mature

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R e a c t i v e S t r e a m s C o m m o n s

I P C

A D D O N S

S p r i n g R x

C O R E

Existential questions

2013: 1.x 2014: 2.x 2016: 3.0

Microservices become the norm

Rocky style revival

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3x Influences and Collaborations

7

R e a c t i v e S t r e a m s C o m m o n s

I P C

A D D O N S

S p r i n g R x

C O R E

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Flux.just("red", "white", "blue") .flatMap(value -> Mono.fromCallable(blockingStuff(value)) .subscribeOn(Schedulers.elastic())) .collect(Result::new, Result::add) .doOnNext(Result::stop) .subscribe(doWithResult);

A smarter Publisher ? Flux !

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Mono, push/pull CompletionStage

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Mono.delayMillis(3000) .map(d -> "Spring 4") .or(Mono.delayMillis(2000).map(d -> "Spring 5")) .then(t -> Mono.just(t+ " world")) .elapsed() .block();

Non!

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Mono, push/pull CompletionStage

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Mono.delayMillis(3000) .map(d -> "Spring 4") .or(Mono.delayMillis(2000).map(d -> "Spring 5")) .then(t -> Mono.just(t+ " world")) .elapsed() .subscribe();

Oui!

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ONE JAR reactor-core.jar

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3x Simpler API Where Flux and Mono live

Make task execution great again and FIFO

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Execution Model Freedom

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Synchronous

Asynchronous

Scheduler / Scheduler.Worker

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3x more focus on Javadoc

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http://projectreactor.io/core/docs/api

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Learning to Flux & Mono

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https://spring.io/blog/2016/06/07/notes-on-reactive-programming-part-i-the-reactive-

landscape

https://spring.io/blog/2016/06/13/notes-on-reactive-programming-part-ii-writing-some-code

https://spring.io/blog/2016/07/20/notes-on-reactive-programming-part-iii-a-simple-http-server-

application

Just browse spring.io/blog already

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Bridge Existing Asynchronous CodeMono<String> response = Mono.create(emitter -> { HttpListener listener = event -> { if (event.getResponseCode() >= 400) { emitter.error(new RuntimeExeption("Failed")); } else { String body = event.getBody(); if (body.isEmpty()) { emitter.complete(); } else { emitter.complete(body.toLowerCase()); } } }; client.addListener(listener); emitter.setCancellation(() -> client.removeListener(listener)); });

•

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Also exists for Flux of N items

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Operation Fusion

• Reactor has a mission to limit the overhead in stack and message passing

• 2 key categories : • “Macro Fusion” : merge operators in one (assembly time) • “Micro Fusion” : avoid queue creation and short circuit where

possible request lifecycle.

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Starve CPU’s with ParallelFlux…

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Flux.range(1, 100000) .parallel(3) .runOn(Schedulers.parallel()) .collect(ArrayList::new, ArrayList::add) .sequential() .reduce(0, (a, b) -> a + b.size()) .subscribeWith(TestSubscriber.create()) .await(Duration.ofSeconds(5)) .assertValues(100_000) .assertNoError() .assertComplete();

•

x3

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Efficient and micro bench ready

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https://github.com/akarnokd/akarnokd-misc/tree/master/src/jmh/java/hu/akarnokd/comparison

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Bridge Fabulous RxJava 1

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RxJava1Adapter

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Bridge Java 9 Reactive Streams

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JdkFlowAdapter

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Play with Reactor Core .NET

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https://www.nuget.org/packages/Reactor.Core/

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Backpressure for JS: Reactor Core TypeScript

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https://www.npmjs.com/package/reactor-core-js

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BREXIT ?

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DONALD TRUMP ?

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EVERYTHING REACTIVE ?

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Learn More. Stay Connected.

@ProjectReactor@smaldini

http://github.com/reactor

@springcentral spring.io/blog

@pivotal pivotal.io/blog

@pivotalcf http://engineering.pivotal.io