This document discusses reactive microservices and Spring 5. It introduces reactive streams as a standard for asynchronous stream processing with back pressure. It describes Project Reactor as a reactive streams library for the JVM that is compatible with RxJava. Spring 5 supports reactive repositories, controllers, and web frameworks that integrate with reactive data sources, HTTP servers, and can convert between Mono, Flux, Observable, and CompletableFuture types. Spring 5 GA release was on July 27, 2017 and added reactive support across many Spring projects.

1. Reactive Microservices
And Spring 5
Jay Lee(jaylee@pivotal.io)
Senior Platform Architect

2. Jay Lee(이창재)
Senior Platform Architect

3. Reactive Streams

4. Reactive Programming in One Picture

5. Reactive Programming is paradigm oriented
around data flows and propagation of change

7. Reactive Streams is an initiative to provide a
standard for asynchronous stream processing
with non-blocking back pressure. This
encompasses efforts aimed at runtime
environments (JVM and JavaScript) as well as
network protocols.
- http://www.reactive-streams.org/

8. Asynchronous?
http://www.ibm.com/developerworks/library/l-async/figure4.gif

9. Asynchronous?
http://www.ibm.com/developerworks/library/l-async/figure5.gif

10. Reactive Streams is an initiative to provide a
standard for asynchronous stream processing
with non-blocking back pressure. This
encompasses efforts aimed at runtime
environments (JVM and JavaScript) as well as
network protocols.
- http://www.reactive-streams.org/

11. Publisher Subscriber
Stream Processing

12. Publisher Subscriber
Stream Processing
3msg/sec 1msg/sec

13. Publisher Subscriber
Stream Processing
3msg/sec 1msg/sec

14. Publisher Subscriber
Stream Processing
3msg/sec 1msg/sec

15. Publisher Subscriber
Stream Processing
3msg/sec 1msg/sec

16. Publisher Subscriber
Stream Processing With Back Pressure
3msg/sec 1msg/sec
Hey, I can only take 1msg/sec

17. Publisher Subscriber
Stream Processing With Back Pressure
1msg/sec 1msg/sec
Hey, I can only take 1msg/sec
Gotcha!!

18. Back Pressure in real world

19. Back Pressure in real world

21. Reactive Stream Implementation
Ÿ RxJavaReactiveStreams with RxJava 1.x 2.x
Ÿ Project Reactor
Ÿ Vert.x
Ÿ Akka Streams
Ÿ Slick
Ÿ …

22. Project Reactor

23. Journey of Project Reactor

24. 2

25. 2

26. 2

27. Project Reactor

28. Project Reactor
Ÿ Reactive Streams Library for JVM
Ÿ Declarative operations similar to Java 8 Streams
Ÿ Flux and Mono reactive composable API types
Ÿ Compatible with RxJava,

29. Reactive Streams
http://javasampleapproach.com/java/java-9/java-9-flow-api-reactive-streams

30. Reactive Streams: Mono – sequence of 0..1Mono

31. Mono<String> emptyMono() {
return Mono.empty(); }
Mono<String> fooMono() {
return Mono.just("foo"); }
Mono<String> toUpperCase(Mono<String> mono) {
return mono.map(String::toUpperCase); }
Mono BasicMono Basic

32. Reactive Streams: Flux – sequence of 0..NFlux

33. Flux Basic
Flux<String> emptyFlux() {
return Flux.empty();}
Flux<String> fooBarFluxFromValues() {
return Flux.just("foo", "bar");}
Flux<String> fooBarFluxFromList() {
return Flux.fromIterable(Arrays.asList("foo", "bar")); }
Flux<String> toUpperCase(Flux<String> flux) {
return flux.flatMap(s -> Mono.just(s.toUpperCase())); }
Flux Basic

34. Spring 5

35. Spring 5 - Reactive Repository
public interface ReactivePersonRepository extends ReactiveCrudRepository<Person,
String> {
Flux<Person> findByLastname(Mono<String> lastname);
Mono<Person> findByFirstnameAndLastname(String firstname, String lastname);
}
@EnableReactiveMongoRepositories
public class AppConfig extends AbstractReactiveMongoConfiguration {
}
(Repository)

36. Ÿ MongoDB
Ÿ Cassandra
Ÿ Redis
Ÿ Couchbase
Spring 5 – Spring Data Compatible

37. Ÿ Oracle, MySQL
Ÿ A database access API for Java that does not block user
threads
Ÿ Target high throughput apps
From: JDBC Next by Douglas Surber (JavaOne 2016)
NonBlocking JDBC Access to Oracle,Mysql

38. public void trivialSelect(DataSource ds, List<Integer> result)
{
String sql = "select <<id>>, <<name>>, <<answer>> " + "from tab where answer = <<i target>>";
try (Connection conn = ds.getConnection()) {
conn.<List<Integer>>rowOperation(sql)
.set("target", 42, JdbcType.NUMERIC)
.rowAggregator( (ignore, row) -> {
result.add(row.get("id", Integer.class));
return null;
} )
.submit(); }}
NonBlocking JDBC Example

39. Spring 5 - Reactive Web Controller
@Controller
Public class UserController {
private final UserRepository userRepository;
public UserController(UserRepository userRepository) {
this.userRepository = userRepository; }
@GetMapping(“/users/{id}”)
public Mono<User> getUser(@PathVariable Long id) {
return this.userRepository.findOne(id);}
@PostMapping(“/users”)
public Mono<Void> addUser(@RequestBody User user) {
return this.userRepository.save(user);}
}
(Controller) - (Repository)

40. Spring 5 - Reactive Web Framework
public interface ReactiveHttpInputMessage extends HttpMessage {
Flux<DataBuffer> getBody();
}
public interface ReactiveHttpOutputMessage extends HttpMessage {
Mono<Void> writeWith(Publisher<DataBuffer> body);
}
(Framework) - (Controller) - (Repository)

41. Spring 5 – Reactive HTTP Server
Ÿ Servlet 3.1 Bridge
Ÿ Undertow in spring-web
Ÿ Reactor Netty
Ÿ RxNetty
Ÿ Reactive Stream Bridge to Tomcat and Jetty
(HTTP Server) - (Framework) - (Controller) - (Repository)

42. Observable<User> fromFluxToObservable(Flux<User> flux) {
return Observable.fromPublisher(flux);
}
Flux<User> fromObservableToFlux(Observable<User> observable) {
return Flux.from(observable.toFlowable(BackpressureStrategy.BUFFER));
}
RxJava Observable and Reactor

43. CompletableFuture<User> fromMonoToCompletableFuture(Mono<User>
mono) {
return mono.toFuture();
}
Mono<User> fromCompletableFutureToMono(CompletableFuture<User>
future) {
return Mono.fromFuture(future);
}
Mono and CompletableFuture

44. Summary
• Spring 5.0 GA 곧 출시!!

45. Ÿ Reactive Streams
Ÿ Microservices and Reactive Streams
Ÿ Spring 5.0 GA – Jul 27, 2017
Ÿ Being adopted for Boot, Security, Data, Cloud, Integration,
etc
Summary