Users should know that for 1.16.0:

a) if istio is enabled with mTLS, metrics for Serving are disabled by default because Service mesh blocks Prometheus from scraping them.

b) If they want to enable them they have to do the following:

• specify `prometheus` as the backend explicitly in the knative serving instance by adding (this avoids disabling metrics by default):

  apiVersion: operator.knative.dev/v1alpha1
  kind: KnativeServing
  metadata:
    name: knative-serving
  spec:
    config:
      observability:
        metrics.backend-destination: "prometheus"
  .....
  

• apply the following net policy to allow traffic from the Prometheus ns:

  apiVersion: networking.k8s.io/v1
  kind: NetworkPolicy
  metadata:
    name: allow-from-openshift-monitoring-ns
    namespace: knative-serving
  spec:
    ingress:
    - from:
      - namespaceSelector:
          matchLabels:
            name: "openshift-monitoring"
    podSelector: {}
    policyTypes:
    - Ingress
  

• finally modify the default smcp in istio-system ns and add:

  spec:
    proxy:
      networking:
        trafficControl:
          inbound:
            excludedPorts:
            - 8444