Regression: tracing context lost with WebTestClient

[beltram]

Hi,
Once using Sleuth and injecting Tracing headers in a WebTestClient I was able to retrieve them in Reactor's context later on like this :

// Test
webTestClient.get()
    .uri("/api/tracing")
    .header("X-B3-TraceId", "463ac35c9f6413ad48485a3953bb6124")
    .header("X-B3-SpanId", "a2fb4a1d1a96d312")

// Controller
@GetMapping
    fun spanId(): Mono<String> {
        return Mono.subscriberContext()
                .filter { it.hasKey(Span::class.java) }
                .map { it[Span::class.java].context() }
                .map { it.spanIdString() }
    }

This worked with spring-test 5.2.1.RELEASE but no longer with 5.2.2.RELEASE.

What happens is that a new Span is created here because Context lacks original Span.

I think root cause comes from this commit or this one in HttpHandlerConnector.

I've setup a reproducer here. Thank you 😄

Affects: Spring Framework 5.2.2.RELEASE

[rstoyanchev]

Even though the changes from #23936 clearly have this effect, that doesn't mean the root cause is in the Spring Framework. I don't see anything in our changes that should be problematic and I'm not familiar enough with how Sleuth is implemented to be able to debug or even reason about the issue.

So please create re-open this against Sleuth and also link the two so I can follow it. I'm quite happy to help figure out what the issue is.