Support Spring Web MVC in library instrumentation

[mateuszrzeszutek]

Part of #7312

This is pretty much a copy of the spring-webvmc-5.3:library module with s/javax/jakarta/ applied. I'm planning on removing the 5.3 instrumentation after #7312 is done.

[marcingrzejszczak]

Why not just redirect work to the inbuilt micrometer observation mechanism (https://docs.spring.io/spring-framework/docs/current/reference/html/integration.html#integration.observability)? That way you don't have to maintain the integration at all 🤷 ?

[mateuszrzeszutek]

The Spring conventions are very different from OTel, we'd have to implement and inject our own. KeyValues only support string values, so to implement OTel conventions correctly we'd have to do add some magic that converts e.g. ports to integers.

I agree with you that the OTel javaagent needs to support Micrometer tracing at some point in time, but right now it's much easier for us to slightly modify the existing instrumentations to work with Spring 6/Spring Boot 3. Implementing a tracing bridge might also take quite a while -- I mean, it took me over a month to implement a MeterRegistry bridge and it's still not exactly perfect (which is honestly the fault of the OTel metrics API, namely the impossibility of defining histogram buckets in the API).

[marcingrzejszczak]

The Spring conventions are very different from OTel, we'd have to implement and inject our own. KeyValues only support string values, so to implement OTel conventions correctly we'd have to do add some magic that converts e.g. ports to integers.

I understand.

I agree with you that the OTel javaagent needs to support Micrometer tracing at some point in time, but right now it's much easier for us to slightly modify the existing instrumentations to work with Spring 6/Spring Boot 3.

Makes sense!

Implementing a tracing bridge might also take quite a while -- I mean, it took me over a month to implement a MeterRegistry bridge and it's still not exactly perfect (which is honestly the fault of the OTel metrics API, namely the impossibility of defining histogram buckets in the API).

The tracing bridge is already there https://github.com/micrometer-metrics/tracing/tree/main/micrometer-tracing-bridges/micrometer-tracing-bridge-otel