Side-by-side metrics collection with Prometheus and OTel

[andreminelli]

Is there a guide (or tip) on how to allow that (legacy) Prometheus metrics and (new) OTel metrics could be 'merged' in a single Prometheus-format output? This would allow a much simpler migration path, until all legacy Prometheus instrumentation could be changed to OTel API.

Prometheus library has a public method that exports its data to an arbitrary Stream, but OTel doesn't have such support (PrometheusExporter class is internal at this time).

[andreminelli]

I just discovered that prometheus-net also exports metrics from System.Diagnostics.Metrics, so this already works.