Wrong observation status tag when a Not Found in a webflux application

[JordiMartinezVicent]

Spring Boot Version: 3.1.6

Given a webflux application with metrics enabled, when a request is done to a non existing endpoint, the status tag is 200, instead of 404 (not found)

I have attached a sample application.
webflux-metrics.zip

To reproduce the issue

• Start the application
• Make a request to a non existing endpoint, for example to http://localhost:8080/non-existing
• Check the metrics to the prometheus endpoint http://localhost:8080/actuator/prometheus

http_server_requests_seconds_count{error="ResponseStatusException",exception="ResponseStatusException",method="GET",outcome="SUCCESS",status="200",uri="/**",} 1.0
http_server_requests_seconds_sum{error="ResponseStatusException",exception="ResponseStatusException",method="GET",outcome="SUCCESS",status="200",uri="/**",} 0.005408

Notice the tag status="200"

Notice that with SpringBoot 3.1.5, it works correctly, having the status=404

[bclozel]

This is due to a regression introduced by #31417.

[JordiMartinezVicent]

@bclozel there would be some kind of workaround until the 6.0.15 is released?

[bclozel]

@JordiMartinezVicent there is no workaround yet as I haven't found a proper fix for this issue and #31706 which is related.