Expose cloud function with REST API & RSocket with R2DBC as backend.

• RPC: Function<String, Mono>, Function<Mono, Mono>

 public Function<String, String> uppercase() { return value -> value.toUpperCase(); } public Function<Flux<String>, Flux<String>> reactiveUpperCase() {	return flux -> flux.map(val -> val.toUpperCase()); } 

• request/stream: Function<String, Flux>
• fire_and_forget/metadataPush: Function<String, Void>

public Consumer<Person> log() { return person -> { System.out.println("Received: " + person); }; } public Function<Flux<?>, Mono<Void>> log() {	return flux -> flux.map(..).filter(..).then(); } 

• channel: Function<Flux>, Flux

@Controller public class Greeter implements Function<String, Mono<String>> { @Override @MessageMapping("greeter") public Mono<String> apply(String name) { return Mono.just("Hello " + name); } }

• Spring Cloud Function: https://spring.io/projects/spring-cloud-function
• Spring Cloud Function Docs: https://cloud.spring.io/spring-cloud-static/spring-cloud-function/3.0.0.RELEASE/reference/html/index.html
• spring-cloud-function-rsocket: https://github.com/spring-cloud/spring-cloud-function/tree/master/spring-cloud-function-rsocket
• Spring Data R2DBC: https://spring.io/projects/spring-data-r2dbc
• Event-Driven with Spring Cloud Function and Spring Cloud Stream: https://learning.oreilly.com/videos/event-driven-with-spring/10000MNLV2021128/
• spring-cloud-function-grpc: https://github.com/spring-cloud/spring-cloud-function/tree/main/spring-cloud-function-adapters/spring-cloud-function-grpc
• Functions and Spring Cloud Stream Applications for data driven microservices: https://github.com/spring-cloud/stream-applications