Fausto David Suarez Rosario

> @faustodavid Any chance for merging soon? its already 2 weeks since 2.4 release Thank you Hi @edgarkz , after @joe-elliott comments I changed the code a bit, so I...

I think you forgot to increase the metrics, and we might not need the counter`aspnetcore_requests_total` because we already have this info`aspnetcore_requests_duration_seconds_count`. But the concurrent connections gauge is very handy :)

> Thanks, added the missing inc/dec. Not too sure how to test this properly though.. Yeah, testing might be challenging right now, maybe adding black-box testing or introducing interfaces, but...

Each `DiagnosticListenerHandler` has a static class `PrometheusCounters`, I would like to propose to move the creation of the counter a level up without making them static, this can help us...

Do you have a preference on how to test the code? Let me know if you prefer to don't introduce the new interfaces because of the extra complexity/perf-impact, I can...

I think it is better if you don't allow synchronous IO, because it can impact your performance. You can implement the solution from this PR or the solution from @ramon-garcia...