LogSpanHandler uses JUL logging

[mpb7h]

Describe the Bug

We have applications which currently are not sending traces to an endpoint (by design - right now we just want traceIds in our logs for correlating requests). When no reporters are configured, the LogSpanHandler is attached by default. This handler uses JUL logging at an INFO level to log the span. The default JRE logging configuration means that these messages are printed to stdout.

This is problematic - unless we explicitly now include a logging.properties file and ensure it's loaded in our code, we get logs from this handler for every request which do not honour the log format of the rest of our application logging.

Steps to Reproduce

Create a basic Micronaut application as per https://guides.micronaut.io/latest/micronaut-microservices-distributed-tracing-zipkin-gradle-kotlin.html, but remove the http configuration

Expected Behaviour

There are two possibilities here:

• Use a logging facade so that log messages from the library honour my own logging configuration
• Log at DEBUG level, so traces are not logged by default

[mpb7h]

FYI I realised that I can set the sampler probability to zero (`tracing.zipkin.sampler.probability' in Micronaut terms) to get the behaviour that I want, but the original point still stands I think.