Add generics to metric instruments & instrument provider

[leewoobin789]

There are no differences between float64 and int64 in each async instrument and sync instrument.

it would immensely help on simplifying the implementation of further features in go-contrib, avoiding many boilerplates.

[linux-foundation-easycla]

• ❌ The commit (edb3716, fc0d1c5). This user is missing the User's ID, preventing the EasyCLA check. Consult GitHub Help to resolve.For further assistance with EasyCLA, please submit a support request ticket.

[codecov]

Codecov Report

Merging #3406 (edb3716) into main (3dd4e81) will increase coverage by 0.0%.
The diff coverage is 92.4%.

❗ Current head edb3716 differs from pull request most recent head fc0d1c5. Consider uploading reports for the commit fc0d1c5 to get more accurate results

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #3406   +/-   ##
=====================================
  Coverage   77.9%   77.9%           
=====================================
  Files        164     164           
  Lines      11361   11361           
=====================================
+ Hits        8855    8859    +4     
+ Misses      2307    2303    -4     
  Partials     199     199           

Impacted Files	Coverage Δ
sdk/metric/instrument.go	83.3% <ø> (ø)
metric/internal/global/instruments.go	54.3% <72.2%> (ø)
metric/internal/global/meter.go	96.4% <100.0%> (ø)
metric/noop.go	100.0% <100.0%> (ø)
sdk/metric/instrument_provider.go	80.0% <100.0%> (ø)
sdk/metric/meter.go	100.0% <100.0%> (ø)
exporters/jaeger/jaeger.go	91.1% <0.0%> (+0.8%)	⬆️
sdk/trace/batch_span_processor.go	81.1% <0.0%> (+0.8%)	⬆️

[MrAlias]

it would immensely help on simplifying the implementation of further features in go-contrib, avoiding many boilerplates.

Can you please justify this statement?

[MrAlias]

This will not support users using Go < 1.18.

[leewoobin789]

@MrAlias
fair point. however i suppose that the support under 1.18 is anyway abandoned in the current version, because the code already makes use of generics ( for instance sdk/metric/instrument.go). doesn't it?

The simplication could occur in the way that you don't need to define same function twice, when it comes to handling both int64 and float64 types.

Thanks!

p.s.
btw. somehow EasyCLA does not accept me as contributor. I have already registered as individual contributor in opentelemetry-collector-contrib, however I am facing a weird issue that redirects me back to my last (closed) PR in contrib repo.

[MrAlias]

@MrAlias fair point. however i suppose that the support under 1.18 is anyway abandoned in the current version, because the code already makes use of generics ( for instance sdk/metric/instrument.go). doesn't it?

The SDK is a separate module from the API, it does not impose a limitation on the API. This is by design: https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/overview.md.

Please see the existing discussion on the topic and the ultimate SIG decision: #2494 (comment)

[leewoobin789]

@MrAlias
I see. Thank you for the information. I will close down this PR.