[roskilli]

Thanks for the detailed response.

I am surprised there is no gauge update API yet (instead of callback only), this is a common use case and I don't think folks should be expected to implement their own. Especially since it will lead to potentially allocation heavy bespoke implementations, depending on use case given mutex+callback+other structures that likely need to be heap allocated (vs a simple int64 wrapper with atomic update/load APIs).

Also I would just say that the fact the APIs differ a lot to more common popular Prometheus client libraries does beg the question of do we need more complicated APIs that folks have a harder time using. Now is the time to modernize these before everyone is instrumented with some generation of a client library that would need to change/evolve. The whole idea of an OTel SDK is instrument once and then avoid needing to re-instrument again when making changes to your observability pipeline and where it's pointed. This becomes a hard sell if OTel SDK needs to shift fairly significantly to support more popular & common use cases with more typical APIs and by doing so leaves a whole bunch of OTel instrumented code that needs to be modernized to a different looking API.