onFailure() not triggering on WebApplicationException in Vert.x reactive WebClient

Question

I'm running Quarkus 2.7.0.CR1 with this code:

 return httpRequest.sendBuffer(createBuffer())
                   .onSubscription()
                       .invoke(() -> metricsRecorder.start(METRICS_NAME))
                   .onFailure()
                       .recoverWithUni(failure -> fetchWithOtherCredentials())
                   ...

onFailure() triggers if port in URL is not responding at all. But when returning HTTP 500 from WireMock this code just throws WebApplicationException with status 500 without triggering onFailure() . This is the exception that triggers onFailure() :

io.netty.channel.AbstractChannel$AnnotatedConnectException: Connection refused: localhost/127.0.0.1:8085

AnnotatedConnectException seems to be checked exception but in this example IllegalArgumentException is used which is RuntimeException like WebApplicationException .

I thought onFailure() should trigger on any exception. Any ideas what is going on? I have tested with @QuarkusTest and also by running Quarkus locally with mvn compile quarkus:dev .

Answer 1

HttpRequest.sendBuffer() returns a Uni<HttpResponse<T>> . When the server responds with status 500 , the Web Client does not emit a failure, it emits an HttpResponse with status code 500 .

You should inspect the response, like this:

Uni<HttpResponse> uni = httpRequest
    .sendBuffer(createBuffer())
    .onItem().transformToUni(res -> {
        if (res.statusCode() == 200 && res.getHeader("content-type").equals("application/json")) {
          // Do something with JSON body and return new Uni
        } else {
          // Generate failure as Uni
        }
    });

Another option is to use response predicates :

Uni<HttpResponse> uni = httpRequest
    .expect(ResponsePredicate.SC_SUCCESS)
    .expect(ResponsePredicate.JSON)
    .sendBuffer(createBuffer());

In this case, the returned Uni<HttpResponse> is successful only when the response has status code 200 and a JSON body, otherwise it is failed.