dotnet/extensions metric names to follow some convention

[klauco]

Currently, the metric names are using backslashes. OTel uses dots. We need to go through the metrics and ensure we stick to the same naming convention (and semantic grouping as part of the metric name).

Proposal:

1. use dots instead of backslashes
2. follow pluralization rules as described in https://opentelemetry.io/docs/specs/otel/metrics/semantic_conventions/

[klauco]

cc @geeknoid @xakep139 @noahfalk

[xakep139]

As @noahfalk suggested, we should consider using instrument names that follow pattern like: aspnetcore.header_parsing.parse_errors instead of HeaderParsing.ParsingErrors that we have currently.

[xakep139]

I can apply this pattern within #4342, but we need to reach an agreement first

[martintmk]

As @noahfalk suggested, we should consider using instrument names that follow pattern like: aspnetcore.header_parsing.parse_errors instead of HeaderParsing.ParsingErrors that we have currently.

We have also aligned the naming in Polly with OpenTelemetry by using the convention as suggested above. See App-vNext/Polly#1583 for reference.

Also attributes names were changed:

• event_name -> event.name
• exception_name -> exception.type (this one is standard in OT)
• etc

[xakep139]

Up-to-date conventions are here: https://github.com/open-telemetry/semantic-conventions/blob/main/docs/general/metrics.md

[joperezr]

@xakep139 is working on this this week, and the target is to merge by next week.

[joperezr]

Update:

• PR seems in a good state, we are just waiting on a signoff from Ludmila.