Reaktive Server mit Spring WebFlux und Kotlin Coroutines (German)

In this presentation I explain how reactive servers work, what Spring WebFlux is and how Kotlin Coroutines can improve the development of reactive servers.

Transcript

1. Reaktive Server mit Spring WebFlux und Kotlin Coroutines Jochen Kraushaar @KraushaarJochen jochen.kraushaar@bridging-it.de
2. Reaktive Server
3. Client schickt Request Server holt Thread aus Thread Pool Server ordnet Request Thread zu Anwendung arbeitet im Thread Thread wird ggf. blockiert
4. Client schickt Request Server holt Thread aus Thread Pool Server ordnet Request Thread zu Anwendung arbeitet im Thread Thread wird ggf. blockiert Kein freier Thread im Pool
5. Client schickt Request Server holt Thread aus Thread Pool Server ordnet Request Thread zu Anwendung arbeitet im Thread Thread blockiert NICHT
6. Reaktiv = Non-Blocking (mit Backpressure)
7. Reaktive Streams RxJava Project Reactor
8. Spring WebFlux
9. Quelle: https://docs.spring.io/spring/docs/5.2.0.RELEASE/spring-framework-reference/web-reactive.html Copyright © 2002 - 2019 Pivotal, Inc. All Rights Reserved.
10. Mono Project Reactor 0..1 Elemente „Optional auf Steroide“
11. @GetMapping("/{id}") fun findAvailableProduct(@PathVariable id: Int): Mono<AvailableProduct> = productRepository.getProductById(id) .filter { !it.deleted } .map { AvailableProduct(it) }
12. Flux Project Reactor 0..N Elemente Reaktiver Stream
13. @GetMapping("/") fun findAllAvailableProducts(): Flux<AvailableProduct> = productRepository.getAllProducts() .filter { !it.deleted } .map { AvailableProduct(it) }
14. Achtung! Deklarativ statt Imperativ Exceptions als Rückgabe Reaktiver Stack Kein JDBC
15. R2DBC Spezifikation Version 1.0.0.RC1 H2 PostgreSQL Microsoft SQL Server MySQL
16. Kotlin Coroutines
17. Warum? Imperativ „Leichtgewichtige Threads“ Suspending Functions
18. Coroutine Scope
19. fun main() = runBlocking { repeat(100_000) { // launch a lot of coroutines launch { delay(1000L) print(".") } } } Quelle: https://kotlinlang.org/docs/reference/coroutines/basics.html, Apache 2 License
20. suspend
21. suspend fun doSomethingUsefulOne(): Int { delay(1000L) // pretend we are doing something useful here return 13 } suspend fun doSomethingUsefulTwo(): Int { delay(1000L) // pretend we are doing something useful here, too return 29 } Quelle: https://kotlinlang.org/docs/reference/coroutines/composing-suspending-functions.html, Apache 2 License
22. async / await
23. fun main() = runBlocking<Unit> { val time = measureTimeMillis { val one = async { doSomethingUsefulOne() } val two = async { doSomethingUsefulTwo() } println("The answer is ${one.await() + two.await()}") } println("Completed in $time ms") } Quelle: https://kotlinlang.org/docs/reference/coroutines/composing-suspending-functions.html, Apache 2 License
24. Mono vs. suspend
25. @GetMapping("/{id}") fun findAvailableProduct(@PathVariable id: Int): Mono<AvailableProduct> = productRepository.getProductById(id) .filter { !it.deleted } .map { AvailableProduct(it) }
26. @GetMapping("/{id}") suspend fun findAvailableProduct(@PathVariable id: Int): AvailableProduct? { val product = productRepository.getProductById(id) ?: return null return AvailableProduct(product) }
27. Flux vs. Flow vs. suspend
28. @GetMapping("/") fun findAllAvailableProducts(): Flux<AvailableProduct> = productRepository.getAllProducts() .filter { !it.deleted } .map { AvailableProduct(it) }
29. @GetMapping("/") fun findAllAvailableProducts(): Flow<AvailableProduct> = productRepository.getAllProducts() .filter { !it.deleted } .map { AvailableProduct(it) }
30. @GetMapping("/") suspend fun findAllAvailableProducts(): List<AvailableProduct> { val products = productRepository.getAllProducts().toList() return products.filter { !it.deleted }.map { AvailableProduct(it) } }
31. Fazit & Mehr
32. Brauche ich Reaktive Server?
33. Gut für moderne Cloud- Architekturen
34. Aber… Keine Blocking APIs Anderes Programmiermodell Kotlin Coroutines nicht erforderlich, aber empfehlenswert
35. Wie gut funktioniert Kotlin mit Spring?
36. Sehr gut „First-Class Support“ Spring Initializr Spring Boot KoFu Kotlin Coroutines
37. Danke! Quellen ▪ https://github.com/ReactiveX/RxJava ▪ https://projectreactor.io/ ▪ https://r2dbc.io/ ▪ https://docs.spring.io/spring/docs/current/spring-framework-reference/web-reactive.html ▪ https://www.baeldung.com/spring-boot-kotlin-coroutines ▪ https://spring.io/blog/2019/04/12/going-reactive-with-spring-coroutines-and-kotlin-flow ▪ https://kotlinlang.org/docs/reference/coroutines/ Jochen Kraushaar @KraushaarJochen jochen.kraushaar@bridging-it.de
38. B A C K L O G
39. Reaktiv zum Client HTTP (Websockets, Server-Side Events) HTTP/2 TCP UDP