WebFlux: Mono does not invoke onComplete(), but instead cancel() #22952
Description
Affects: 5.1.6.RELEASE
Hello,
How to reproduce:
When I have a simple @RestController:
@GetMapping("monoSuccess")
public Mono<String> monoSuccess(){
return Mono.just("test").log();
}
I can see in the Reactor logs the following:
[ctor-http-nio-3] reactor.Mono.Just.1 : | onSubscribe([Synchronous Fuseable] Operators.ScalarSubscription)
[ctor-http-nio-3] reactor.Mono.Just.1 : | request(unbounded)
[ctor-http-nio-3] reactor.Mono.Just.1 : | onNext(test)
[ctor-http-nio-3] reactor.Mono.Just.1 : | cancel()
This behavior does not match the bahavior of Flux.
@GetMapping("fluxSuccess")
public Flux<String> fluxSuccess(){
return Flux.just("test") .log();
}
reactor.Flux.Just.1 : | onSubscribe([Fuseable] FluxJust.WeakScalarSubscription)
reactor.Flux.Just.1 : | request(1)
reactor.Flux.Just.1 : | onNext(test)
reactor.Flux.Just.1 : | request(32)
reactor.Flux.Just.1 : | onComplete()
My expectation:
- I would expect that Mono and Flux behavior similar.
- I would expect that
onComplete()is invoked instead ofScalarSubscription.cancel()afteronNext.
My problem :
When I do a simple test with my Resilience4j CircuitBreaker operator I can see the expected behavior of Reactor.
StepVerifier.create(
Mono.just("Event")
.log()
.transform(CircuitBreakerOperator.of(circuitBreaker))
.log())
.expectNext("Event")
.verifyComplete();
reactor.Mono.Just.1 - | onSubscribe([Synchronous Fuseable] Operators.ScalarSubscription)
reactor.Mono.CircuitBreaker.2 - onSubscribe(CircuitBreakerSubscriber)
reactor.Mono.CircuitBreaker.2 - request(unbounded)
reactor.Mono.Just.1 - | request(unbounded)
reactor.Mono.Just.1 - | onNext(Event)
reactor.Mono.CircuitBreaker.2 - onNext(Event)
reactor.Mono.Just.1 - | onComplete()
reactor.Mono.CircuitBreaker.2 - onComplete()
My custom CircuitBreaker operator handles onComplete as a successful call and onError as a failed call. But onEvent is just forwarded to the downstream subscriber.
With the current unexpected behavior I have to handle onEvent specially when a Mono is decorated.
Kind regards,
Robert