[Instrumentation.EventCounters] Support long event source names better in EventCounters instrumentation

[lmolkova]

EventCounters instrumentation does not work for several well-known EventSources.

E.g. Microsoft-AspNetCore-Server-Kestrel or most of the counters in Microsoft.AspNetCore.Http.Connections.
It happens because of instrument length limitations (63 symbols).

End users can't do anything about it except republish all events, so we need to find a reasonable way to allow at least well-known event sources. Kestrel counters, for example, are extremely useful and can't be measured in other ways (DiagSource/ActivitySource instrumentation in hosting).

So, EventCounters.Microsoft-AspNetCore-Server-Kestrel. is already 50 chars and it doesn't even include event name.

This change proposes:

• use ec. prefix instead of EventCounters. - It seems less important than event source/event names
• When the instrument name in EventCounters is too long, I suggest abbreviating shorten the event source portion of it:
  ec.Microsoft-AspNetCore-Server-Kestrel.tls-handshakes-per-second -> ec.Microsoft-AspNetCore-Server-Kestr.tls-handshakes-per-second. It generates stable and common name for a single instrument.

Happy to consider other options for shortening the name.

• Appropriate CHANGELOG.md updated for non-trivial changes
• Design discussion issue #

[codecov]

Codecov Report

Merging #740 (5803f8a) into main (005fdb7) will increase coverage by 0.15%.
The diff coverage is 100.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #740      +/-   ##
==========================================
+ Coverage   77.41%   77.56%   +0.15%     
==========================================
  Files         176      176              
  Lines        5299     5308       +9     
==========================================
+ Hits         4102     4117      +15     
+ Misses       1197     1191       -6     

Impacted Files	Coverage Δ
...ons/Internal/ActivityEventAttachingLogProcessor.cs	93.33% <100.00%> (ø)
...trumentation.EventCounters/EventCountersMetrics.cs	85.07% <100.00%> (+7.48%)	⬆️
...ounters/EventCountersInstrumentationEventSource.cs	27.27% <0.00%> (+27.27%)	⬆️

[mic-max]

Thanks for the change, I hadn't realised that some of the well-known counters were going to fail this!
The main point of prefixing with EventCounters. is just to help avoid possible collisions, so I think changing to ec. is fine and saves on the character count.
I agree that if anything needs to be shortened in the instrument name it should be the event source and then if still too long after doing so the SDK can just fail and log its warning.

[Kielek]

Approved, but please add entry to the changelog under unreleased section https://github.com/open-telemetry/opentelemetry-dotnet-contrib/blob/main/src/OpenTelemetry.Instrumentation.EventCounters/CHANGELOG.md
(Short description + link to this PR).

[lmolkova]

@open-telemetry/dotnet-contrib-approvers, if there are no objections, can someone please merge it?

[utpilla]

I have published the package: https://www.nuget.org/packages/OpenTelemetry.Instrumentation.EventCounters/1.0.0-alpha.2