Return trace id from Jaeger in response header

[omerbarlev]

I am using opentelemetry in my python FastAPI application. It sends traces back to Jaeger. Each trace has a unique trace id I can also search for in the Jaeger UI search bar.

I want to return in the response headers that trace id so that later on I can look a trace for a specific request (just take the trace id from the header and search for it in Jaeger UI).

I tried adding a middleware in FastAPI that adds the trace id like that -

class EnrichOpenTelemetryId(BaseHTTPMiddleware):
    def __init__(self, app):
        super().__init__(app)

    async def dispatch(self, request: Request, call_next):
        with tracer.start_span("dummy-span") as span:
            trace_id = str(span.get_span_context().trace_id)

        response = await call_next(request)
        response.headers["X-Trace-Id"] = trace_id

        return response   

There is a new header containing some trace id (e.g - 149906749482483391829634904508866243046) in each request but it's not the one Jaeger uses... (meaning I cannot search on that trace id). Jaeger trace id looks something like that - 8eddc793de380fa76c54557af09538e3.

So how do I get Jaeger trace id?

[yurishkuro]

You're getting an integer back, you need to convert it to hex value.

[omerbarlev]

Hi, thank you.
It seems to be working but now I see there are a lot of new traces created in Jaeger.
I tried adding the trace id like this -

async def dispatch(self, request: Request, call_next):
    with tracer.start_span("dummy-span") as span:
        trace_id = span.get_span_context().trace_id

    response = await call_next(request)
    response.headers["X-Trace-Id"] = format(trace_id, 'x')

    return response

And I do get a the right trace id in the response headers.
But now, there are many "dummy-span" traces created containing almost no data.
I would like those traces to not be created at all...

Here is an example of unwanted created span -

[yurishkuro]

When you initialize the tracer, you give it a context manager, which has a method for retrieving the current span. So you don't need to create a new span just to obtain a trace ID.

[omerbarlev]

amazing, thank you so much!