WebFlux Error Handling

WebFlux Error Handling

• doOnError : 예외 발생시 특정행위를 수행한다.
• onErrorReturn : 예외 발생시 특정 값을 return 한다.
• onErrorResume : 예외 발생시 다른 Flux형태로 return 한다.
• onErrorContinue : 예외 발생시 멈추지 않고 해당 영역만 skip 한다(별도 처리 하지 않는 이상 정상 응답을 return한다).
• onErrorMap : 예외 발생시 다른 Exception으로 변환한다.

doOnError

Source:

@RequestMapping("/error/test")
public Flux<Integer> getNum() {
  return Flux.range(0, 5)
      .map(x -> {
        if (x == 3) {
          throw new IllegalArgumentException("invalid num");
        }
        return x;
      })
      .doOnError(x -> log.error("num generate error"))
      .log();
}

Result:

 INFO 5276 --- [ctor-http-nio-2] reactor.Flux.PeekFuseable.1              : | onSubscribe([Fuseable] FluxPeekFuseable.PeekFuseableSubscriber)
 INFO 5276 --- [ctor-http-nio-2] reactor.Flux.PeekFuseable.1              : | request(unbounded)
 INFO 5276 --- [ctor-http-nio-2] reactor.Flux.PeekFuseable.1              : | onNext(0)
 INFO 5276 --- [ctor-http-nio-2] reactor.Flux.PeekFuseable.1              : | onNext(1)
 INFO 5276 --- [ctor-http-nio-2] reactor.Flux.PeekFuseable.1              : | onNext(2)
ERROR 5276 --- [ctor-http-nio-2] c.e.demo.r4.controller.R4Controller      : num generate error
ERROR 5276 --- [ctor-http-nio-2] reactor.Flux.PeekFuseable.1              : | onError(java.lang.IllegalArgumentException: invalid num)
ERROR 5276 --- [ctor-http-nio-2] reactor.Flux.PeekFuseable.1              : 

onErrorReturn

Source:

@RequestMapping("/error/test")
public Flux<Integer> getNum() {
  return Flux.range(0, 5)
      .map(x -> {
        if (x == 3) {
          throw new IllegalArgumentException("invalid num");
        }
        return x;
      })
      .onErrorReturn(99)
      .log();
}

Result:

 INFO 12068 --- [ctor-http-nio-2] reactor.Flux.OnErrorResume.1             : onSubscribe(FluxOnErrorResume.ResumeSubscriber)
 INFO 12068 --- [ctor-http-nio-2] reactor.Flux.OnErrorResume.1             : request(unbounded)
 INFO 12068 --- [ctor-http-nio-2] reactor.Flux.OnErrorResume.1             : onNext(0)
 INFO 12068 --- [ctor-http-nio-2] reactor.Flux.OnErrorResume.1             : onNext(1)
 INFO 12068 --- [ctor-http-nio-2] reactor.Flux.OnErrorResume.1             : onNext(2)
 INFO 12068 --- [ctor-http-nio-2] reactor.Flux.OnErrorResume.1             : onNext(99)
 INFO 12068 --- [ctor-http-nio-2] reactor.Flux.OnErrorResume.1             : onComplete()

onErrorResume

Source:

@RequestMapping("/error/test")
public Flux<Integer> getNum() {
  return Flux.range(0, 5)
      .map(x -> {
        if (x == 3) {
          throw new IllegalArgumentException("invalid num");
        }
        return x;
      })
      .onErrorResume(exec -> {
        log.error("num generate error");
        return Mono.just(99); //어떤 값으로 return을 할지 상황에 맞게 지정한다.
      })
      .log();
}

Result:

 INFO 8444 --- [ctor-http-nio-2] reactor.Flux.OnErrorResume.1             : onSubscribe(FluxOnErrorResume.ResumeSubscriber)
 INFO 8444 --- [ctor-http-nio-2] reactor.Flux.OnErrorResume.1             : request(unbounded)
 INFO 8444 --- [ctor-http-nio-2] reactor.Flux.OnErrorResume.1             : onNext(0)
 INFO 8444 --- [ctor-http-nio-2] reactor.Flux.OnErrorResume.1             : onNext(1)
 INFO 8444 --- [ctor-http-nio-2] reactor.Flux.OnErrorResume.1             : onNext(2)
ERROR 8444 --- [ctor-http-nio-2] c.e.demo.r4.controller.R4Controller      : num generate error
 INFO 8444 --- [ctor-http-nio-2] reactor.Flux.OnErrorResume.1             : onNext(99)
 INFO 8444 --- [ctor-http-nio-2] reactor.Flux.OnErrorResume.1             : onComplete()

OnErrorContinue

Source:

@RequestMapping("/error/test")
public Flux<Integer> getNum() {
  return Flux.range(0, 5)
      .map(x -> {
        if (x == 3) {
          throw new IllegalArgumentException("invalid num");
        }
        return x;
      })
      .onErrorContinue((exec, num) ->
          log.error("num generate error, number is : {}, error msg : {}", num, exec.getMessage()))
      .log();
}

Result:

 INFO 9728 --- [ctor-http-nio-2] reactor.Flux.ContextStart.1              : | onSubscribe([Fuseable] FluxContextStart.ContextStartSubscriber)
 INFO 9728 --- [ctor-http-nio-2] reactor.Flux.ContextStart.1              : | request(unbounded)
 INFO 9728 --- [ctor-http-nio-2] reactor.Flux.ContextStart.1              : | onNext(0)
 INFO 9728 --- [ctor-http-nio-2] reactor.Flux.ContextStart.1              : | onNext(1)
 INFO 9728 --- [ctor-http-nio-2] reactor.Flux.ContextStart.1              : | onNext(2)
ERROR 9728 --- [ctor-http-nio-2] c.e.demo.r4.controller.R4Controller      : num generate error, number is : 3, error msg : invalid num
 INFO 9728 --- [ctor-http-nio-2] reactor.Flux.ContextStart.1              : | onNext(4)
 INFO 9728 --- [ctor-http-nio-2] reactor.Flux.ContextStart.1              : | onComplete()

onErrorMap

Source:

@RequestMapping("/error/test")
public Flux<Integer> getNum() {
  return Flux.range(0, 5)
      .map(x -> {
        if (x == 3) {
          throw new IllegalArgumentException("invalid num");
        }
        return x;
      })
      .onErrorMap(exec -> {
        log.error("num generate error, error msg : {}", exec.getMessage());
        throw new RuntimeException("change error type");
      })
      .log();
}

Result:

 INFO 14204 --- [ctor-http-nio-2] reactor.Flux.OnErrorResume.1             : onSubscribe(FluxOnErrorResume.ResumeSubscriber)
 INFO 14204 --- [ctor-http-nio-2] reactor.Flux.OnErrorResume.1             : request(unbounded)
 INFO 14204 --- [ctor-http-nio-2] reactor.Flux.OnErrorResume.1             : onNext(0)
 INFO 14204 --- [ctor-http-nio-2] reactor.Flux.OnErrorResume.1             : onNext(1)
 INFO 14204 --- [ctor-http-nio-2] reactor.Flux.OnErrorResume.1             : onNext(2)
ERROR 14204 --- [ctor-http-nio-2] c.e.demo.r4.controller.R4Controller      : num generate error, error msg : invalid num
ERROR 14204 --- [ctor-http-nio-2] reactor.Flux.OnErrorResume.1             : onError(java.lang.RuntimeException: change error type)

[참고링크]
[Webflux Tip] 3. Webflux Error 처리! . (n.d.). https://akageun.github.io/2019/07/26/spring-webflux-tip-3.html.