OpenTelemetry Agent (auto-instrumentation) and Quarkus

[joschi]

The Using OpenTelemetry guide says right at the beginning:

The use of the OpenTelemetry Agent is not needed nor recommended. Quarkus Extensions and the libraries they provide, are directly instrumented. That agent doesn’t work with native mode.

While this works for libraries directly supported by Quarkus and the OpenTelemetry extension, the use of the OpenTelemetry Agent might have some use after all.

We're using Quarkus in a JVM-based application (no native image) and are using some 3rd-party libraries which are using for example HttpURLConnection under the hood. The OpenTelemetry Agent would allow to instrument this HTTP client without much effort or writing an additional adapter for the 3rd-party library.

What are the caveats of using the OpenTelemetry Agent with a Quarkus application and how would it work when using the Quarkus OpenTelemetry extension, too?

Can they even be used at the same time?

[quarkus-bot[bot]]

/cc @brunobat (opentelemetry), @radcortez (opentelemetry)

[brunobat]

@joschi, the agent and the extension must not be used at the same time. They will conflict with each-other.

It is possible to use the agent with a Quarkus application running in JVM mode but you wouldn't take advantage of all the Quarkus optimisations. Meaning it's expected the app to take longer to start and you might notice a runtime performance degradation. But you will need to mesure that to be sure.

BTW, HttpURLConnection is not the best client around.

[brunobat]

BTW, we considered supporting that client but we decided not to do it: #42660.
The agent does that with premain() execution... It's easier to implement.

[joschi]

BTW, HttpURLConnection is not the best client around.

I agree, but that's beside the point if another 3rd-party library is using it and I want to instrument it. 😉