Custom Trace ID (from app context) for auto-instrumentation

[IvanVas]

Hi folks, could you help?

I'm using auto-instrumentation with java agent. The app is Jakarta EE (Jersey)
I'd like to change the Trace Id to a custom value instead of new random.
What's the best way?

I checked the extension route, but the extension code is out of main app context.

I checked the manual instrumentation, but can it be combined with auto somehow?

Cheers!

[laurit]

It is possible to replace the IdGenerator https://github.com/open-telemetry/opentelemetry-java/blob/main/sdk/trace/src/main/java/io/opentelemetry/sdk/trace/IdGenerator.java implementation but this implementation would still need to generate ids that are valid according to https://opentelemetry.io/docs/specs/otel/trace/api/#spancontext If you get your id from an external system via http header then you should implement a custom context propagator https://opentelemetry.io/docs/specs/otel/context/api-propagators/ when you have some other reason then consider that perhaps instead of altering the trace id it might be easier to put an extra attribute correlation.id or whatever on the spans that are part of that trace.

[IvanVas]

Thanks for answering!

How do we replace IdGenerator for auto-instrumentation?
How to put the extra attribute, can MDC help?

[trask]

How do we replace IdGenerator for auto-instrumentation?

you need to implement an "agent extension", see https://github.com/open-telemetry/opentelemetry-java-instrumentation/tree/main/examples/extension#extensions

How to put the extra attribute, can MDC help?

it depends, Span.current().setAttribute() is the first thing I'd try