Enable GitLab rails Prometheus metrics by default
Currently Prometheus metrics need to be enabled in ApplicationSettings.
This is somewhat cumbersome, as we can't control this on per host basis, and also adds unnecessary step for most installations to enable them.
In case some metrics would require to be disabled or only enabled under certain conditions Flipper https://github.com/jnunemaker/flipper gem that is currently powering Feature toggles implemented by Gitaly team, seems like good alternative and allowing finer grained control.
With feature toggles, control of whether Prometeus metrics collection and endpoint is enabled or disabled could be either controlled through toggles, or through gitlab.yml
with additional runtime control of a toggle.
Edited by Paweł Chojnacki