apiVersion: v1
kind: Service
metadata:
  name: prometheus
  namespace: monitoring
  annotations:
    prometheus.io/scrape: 'true'
spec:
  type: ClusterIP
  selector:
    name: prometheus
    phase: prod
  ports:
    - name: web
      protocol: TCP
      port: 80
      targetPort: 9090

apiVersion: v1
kind: Service
metadata:
  name: prometheus
  namespace: monitoring
  annotations:
    prometheus.io/scrape: 'true'
    prometheus.io/port: '9090'
spec:
  type: ClusterIP
  selector:
    name: prometheus
    phase: prod
  ports:
    - name: web
      protocol: TCP
      port: 80
      targetPort: 9090

Add explicit annotation for Prometheus port to scrape
Add explicit annotation for Prometheus port to scrape

* Without the prometheus.io/port annotation, Prometheus
service discovery can scrape other Prometheus ports that
may be available.
* For example, Prometheus sidecars (not included) may
be scraped and that may be unintended
