Add node-local-dns headless service

cluster/addons/dns/nodelocaldns/nodelocaldns.yaml

@@ -188,3 +188,24 @@ spec:
           items:
             - key: Corefile
               path: Corefile.base
+---
+# A headless service is a service with a service IP but instead of load-balancing it will return the IPs of our associated Pods.
+# We use this to expose metrics to Prometheus.
+apiVersion: v1
+kind: Service
+metadata:
+  annotations:
+    prometheus.io/port: "9253"
+    prometheus.io/scrape: "true"
+  labels:
+    k8s-app: node-local-dns
+  name: node-local-dns
+  namespace: kube-system
+spec:
+  clusterIP: None
+  ports:
+    - name: metrics
+      port: 9253
+      targetPort: 9253
+  selector:
+    k8s-app: node-local-dns