<p>I have two Ingress (Contour managing Envoy) host header based routes (among others) where both the routes point to the same service.</p>

<pre><code>spec:
  rules:
  - host: foo.com
    http:
      paths:
      - backend:
          serviceName: s1
          servicePort: http
        path: /
  - host: bar.com
    http:
      paths:
      - backend:
          serviceName: s1
          servicePort: http
        path: /
...
  tls:
  - hosts:
    - foo.com
    - bar.com
    secretName: secret
</code></pre>

<p>Is there an existing metric (in Kubernetes, Contour, Envoy) to know how many requests are being routed through each of the two rules, i.e., how many requests are hitting <code>foo.com</code> and how many are hitting <code>bar.com</code>? </p>

<p>Per host metrics is not exposed by envoy for cardinality explosion <a href="https://github.com/envoyproxy/envoy/issues/3351" rel="nofollow noreferrer">issue</a></p>

<p>So your only option is to explore possibility of  application exposing it as Prometheus metrics.</p>
