http.server.active_requests and http.status_code

[JamesNK]

I have a question about http.server.active_requests from https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/metrics/semantic_conventions/http-metrics.md#metric-httpserveractive_requests

http.server.active_requests is an up/down counter with a bunch of tags. One of the tags is the response status code. How does that work with an up/down counter? Response status code isn't known when the counter is incremented, so it can only be applied when the counter is decremented.

If the response status code is added to the tag collection when decrementing the counter, won't that result in two different values, one always increasing, and the other (with the response status code) always decreasing?

[mateuszrzeszutek]

Also it looks like the active requests counter does not have the net.protocol.name & net.protocol.version attributes (unlike all the other HTTP metrics); it used to have http.flavor before we made the change to net.protocol.*.

cc @trask @lmolkova

[trask]

Discussed in Semantic Conventions WG yesterday, and there are two actions we should take:

• remove http.status_code attribute from http.server.active_requests metric
• add a note to general metric semantic conventions about UpDownCounter metrics needing to ensure the same attribute set is always recorded on both up/down