Add trace context/IDs to standard logging (MDC)

[pavolloffay]

Add trace context/IDs to standard logging output. It allows correlating standard logging with traces.

References to requests for this feature in other libraries

• Quarkus https://groups.google.com/forum/#!msg/quarkus-dev/dej_Ref-YAQ/yH_hZysTBQAJ
• Spring Boot Feature: Add Trace to Slf4j MDC opentracing-contrib/java-spring-jaeger#60

To make this possible in MicroProfile there should be agreement on the logging framework supporting MDC and also update to OpenTracing 0.33.0 which exposes trace IDs.

[donbourne]

I would suggest that we could do this without having to tie in any particular requirements to the logging framework. ie. That the OpenTracing / OpenTelemetry specs could indicate that server implementations should include the span and trace IDs in all logs/trace generated within those spans/traces. Then just leave it up to the impls to decide what to use for MDC based on their logging framework.

[pavolloffay]

Then is there a way to test this then?

[donbourne]

A couple of ideas...

1. Perhaps the TCK could add an API to allow checking what gets written to the logs by the target server.
2. The MP OpenTracing API could include a minimal MDC API that vendors could plug their impl into.

I think the 2nd option would be easier to implement, but might seem out of place in the MP OpenTracing API.