Given a Tempo trace and a child span, I’m looking to plot a time-series chart showing the average time it takes for the child span to start (essentially span start time - trace start time). It this possible in Grafana? Context is that I have a “first LLM token returned” span for a project I’m working on, and I want to see how long it takes to reach that point of the trace.
I have created a simple TraceQL query which picks out the trace and the child span into a table:
{resource.service.name="my_service" && name="span_name"}
But I cannot access any of the underlying span information when plotting or using transformations. Closest I got was using the “extract fields” transformation, selecting “nested” as the source and “JSON” as the format, but then when specifying fields to filter the Grafana JSON, the JSON path would always return “not found”.