This issue is intended to serve as a checklist for going GA with our GitLab ruby Prometheus metrics: * [x] Lock down histogram buckets * [x] Attain influxdb metric parity, to the extent that it makes sense (not all prior metrics may be relevant, usable) * [x] Confirm gem is running stable in production * [ ] Deprecate InfluxDB * [ ] Turn on ruby metrics by default (https://gitlab.com/gitlab-org/gitlab-ce/issues/43660) * [ ] Update documentation accordingly * [ ] Update blog post