The original vision was to implement OpenMetrics support in v2 of this library, see #651. By doing it in v2, we can easily fully support OpenMetrics features that are breaking (mostly around name collisions because of (more) "magic" suffixes).

However, there will be a demand for OpenMetrics features (in particular exemplars) in v1, first of all because it will take a while before there will be a stable release of v2, and second because many users won't be ready to migrate their v1 usage to v2 just to get OpenMetrics features.

Thus, this milestone is an umbrella for issues to get (limited) OpenMetrics support into v1 in a compatible fashion.

All of this depends on prometheus/common#214 .