Cannot setup custom sampling with micrometer-tracing-bridge-brave

[sandra-markerud]

Hello,

I am using micrometer tracing for enabling tracing in my spring boot (cloud) application.
Tracing and sampling to zipkin works as expected.
However, now I need to make some custom sampling decisions based on paths, header values or jwt claims from the bearer token within the 'Authorization' header.

Something like:

• never sample requests to '/actuator' endpoints
• never sample requests to some specific endpoints within the application like '/anonymous'
• always sample requests with header 'foo' having value 'bar'
• fallback to configured percentage sampling for everything else

After some research I found that brave seems to offer possibilities to do so:
Brave: https://github.com/openzipkin/brave/blob/master/brave/README.md#custom-sampling

However, I don't seem to be able to wire it correctly within the micrometer setup.

I am aware of the possibility of using 'ObservationPredicate' e.g. for not observing specific paths, but that doesn't cover my needs.
I don'T want/need to manipulate the observation as such but only customize the sampling decisions.

My micrometer-tracing-bridge-brave example:
https://github.com/sandra-markerud/spring-demos/tree/feature/custom-sampling-brave

The SamplingConfiguration tries to setup a HttpTracing that respects the custom rules for sampling. However, the HttpTracing bean is not used, only the Tracing bean instead.

Any help is appreciated.