Implement withSpan method utilities for Mutiny

[brunobat]

Description

This is an issue to create an utility class to make it easier to create custom OpenTelemetry spans when using Mutiny.
See Superheroes utility class: https://github.com/jan-peremsky/quarkus-reactive-otel/blob/c74043d388ec4df155f466f1d6938931c3389b70/src/main/java/com/fng/ewallet/pex/Tracer.java

[quarkus-bot]

/cc @cescoffier (mutiny), @jponge (mutiny)

[arn-ivu]

I have simplified and unit-tested the utility by Jan Peremsky to use mutiny only. You can find it here: https://github.com/arn-ivu/MutinyTracingHelper/blob/main/src/main/java/de/ivu/arn/helper/MutinyTracingHelper.java
Maybe this spares someone else from having to understand all the details.

I am not 100% sure what kind of utility you envision for the official quarkus extension @brunobat. If it's similar to what I did here, I would be happy to open a PR.

[brunobat]

That can help @arn-ivu. Let me ask @cescoffier and @edeandrea if they like the approach you followed.

[edeandrea]

I guess I'm not sure what problem we are trying to solve? Using @WithSpan and @SpanAttributes on methods returning reactive types seems to work fine.

[brunobat]

This doesn't use the annotations and should allow the creation of spans from Mutiny pipelines.

[edeandrea]

Gotcha. What @arn-ivu is doing looks very similar to what I did in https://github.com/quarkusio/quarkus-super-heroes/blob/main/event-statistics/src/main/java/io/quarkus/sample/superheroes/statistics/listener/SuperStats.java

I would think though that this utility class wouldn't need to be a CDI bean, and therefore no need for @ApplicationScoped? Just a utility class with some static helper methods?

I didn't give it a thorough code review nor did I look at the tests.

[arn-ivu]

Hi, happy new year everyone :-)

I have originally uses a CDI-Bean in order to inject the tracer, but I agree that static helper methods make more sense. I have pushed an update to https://github.com/arn-ivu/MutinyTracingHelper/blob/main/src/main/java/de/ivu/arn/helper/MutinyTracingHelper.java

If you would like me to add this code to quarkus-opentelemetry I would appreaciate a hint where (i.e. in what project/packet) it should go (I am not very familiar with the quarkus code base)

[brunobat]

@arn-ivu, I believe it should live in the quarkus-opentelemetry extension itself, pretty much like the CDI utilities, under a new package inside the tracing:
https://github.com/quarkusio/quarkus/tree/main/extensions/opentelemetry/runtime/src/main/java/io/quarkus/opentelemetry/runtime/tracing