I found during Postgres Operator startup that the metrics server is binded to 8080 port but unfortunately it is not exposed by k8s Service.

Actual log line:

time="2021-11-19T12:44:10Z" level=info msg="metrics server is starting to listen" addr=":8080" file="sigs.k8s.io/[email protected]/pkg/log/deleg.go:130" func="log.(*DelegatingLogger).Info" version=5.0.3-0

Prometheus metrics are available at :8080/metrics URL.