(doc): Add a doc as a guidance to help users know how to consume the …

…metrics and integrate it with other solutions

docs/draft/howto/consuming-metrics.md

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+# Consuming Metrics
+
+!!! warning
+Metrics endpoints and ports are available as an alpha release and are subject to change in future versions.
+The following procedure is provided as an example for testing purposes. Do not depend on alpha features in production clusters.
+
+Operator-Controller and CatalogD are configured to export metrics by default. The metrics are exposed on the `/metrics` endpoint of the respective services.
+
+The metrics are secured by [RBAC policies][rbac-k8s-docs], requiring appropriate permissions for access.
+By default, they are exposed over HTTPS, necessitating valid certificates for integration with services like Prometheus.
+The following sections cover enabling metrics, validating access, and integrating with the [Prometheus Operator][prometheus-operator].
+
+Below, you will learn how to enable the metrics, validate access, and integrate with [Prometheus Operator][prometheus-operator].
+
+---
+
+## Operator-Controller Metrics
+
+### Step 1: Enable Access
+
+To enable access to the Operator-Controller metrics, create a `ClusterRoleBinding` to
+allow the Operator-Controller service account to access the metrics.
+
+```shell
+kubectl create clusterrolebinding operator-controller-metrics-binding \
+   --clusterrole=operator-controller-metrics-reader \
+   --serviceaccount=olmv1-system:operator-controller-controller-manager
+```
+
+### Step 2: Validate Access Manually
+
+#### Create a Token and Extract Certificates
+
+Generate a token for the service account and extract the required certificates:
+
+```shell
+TOKEN=$(kubectl create token operator-controller-controller-manager -n olmv1-system)
+echo $TOKEN
+```
+
+#### Deploy a Pod to Consume Metrics
+
+Ensure that the Pod is deployed in a namespace labeled to enforce restricted permissions. Apply the following:
+
+```shell
+kubectl apply -f - <<EOF
+apiVersion: v1
+kind: Pod
+metadata:
+  name: curl-metrics
+  namespace: olmv1-system
+spec:
+  serviceAccountName: operator-controller-controller-manager
+  containers:
+  - name: curl
+    image: curlimages/curl:latest
+    command:
+    - sh
+    - -c
+    - sleep 3600
+    securityContext:
+      runAsNonRoot: true
+      readOnlyRootFilesystem: true
+      runAsUser: 1000
+      runAsGroup: 1000
+      allowPrivilegeEscalation: false
+      capabilities:
+        drop:
+        - ALL
+    volumeMounts:
+    - mountPath: /tmp/cert
+      name: olm-cert
+      readOnly: true
+  volumes:
+  - name: olm-cert
+    secret:
+      secretName: olmv1-cert
+  securityContext:
+    runAsNonRoot: true
+  restartPolicy: Never
+EOF
+```
+
+#### Access the Pod and Test Metrics
+
+Access the pod:
+
+```shell
+kubectl exec -it curl-metrics -n olmv1-system -- sh
+```
+
+From the shell use the `TOKEN` value obtained above to check the metrics:
+
+```shell
+curl -v -k -H "Authorization: Bearer <TOKEN>" \
+https://operator-controller-service.olmv1-system.svc.cluster.local:8443/metrics
+```
+
+Validate using certificates and token:
+
+```shell
+curl -v --cacert /tmp/cert/ca.crt --cert /tmp/cert/tls.crt --key /tmp/cert/tls.key \
+-H "Authorization: Bearer <TOKEN>" \
+https://operator-controller-service.olmv1-system.svc.cluster.local:8443/metrics
+```
+
+---
+
+## CatalogD Metrics
+
+### Step 1: Enable Access
+
+To enable access to the CatalogD metrics, create a `ClusterRoleBinding` for the CatalogD service account:
+
+```shell
+kubectl create clusterrolebinding catalogd-metrics-binding \
+   --clusterrole=catalogd-metrics-reader \
+   --serviceaccount=olmv1-system:catalogd-controller-manager
+```
+
+### Step 2: Validate Access Manually
+
+#### Create a Token and Extract Certificates
+
+Generate a token and get the required certificates:
+
+```shell
+TOKEN=$(kubectl create token catalogd-controller-manager -n olmv1-system)
+echo $TOKEN
+```
+
+#### Deploy a Pod to Consume Metrics
+
+From the shell use the `TOKEN` value obtained above to check the metrics:
+
+```shell
+OLM_SECRET=$(kubectl get secret -n olmv1-system -o jsonpath="{.items[*].metadata.name}" | tr ' ' '\n' | grep '^catalogd-service-cert')
+echo $OLM_SECRET
+```
+
+```shell
+kubectl apply -f - <<EOF
+apiVersion: v1
+kind: Pod
+metadata:
+  name: curl-metrics-catalogd
+  namespace: olmv1-system
+spec:
+  serviceAccountName: catalogd-controller-manager
+  containers:
+  - name: curl
+    image: curlimages/curl:latest
+    command:
+    - sh
+    - -c
+    - sleep 3600
+    securityContext:
+      runAsNonRoot: true
+      readOnlyRootFilesystem: true
+      runAsUser: 1000
+      runAsGroup: 1000
+      allowPrivilegeEscalation: false
+      capabilities:
+        drop:
+        - ALL
+    volumeMounts:
+    - mountPath: /tmp/cert
+      name: catalogd-cert
+      readOnly: true
+  volumes:
+  - name: catalogd-cert
+    secret:
+      secretName: $OLM_SECRET
+  securityContext:
+    runAsNonRoot: true
+  restartPolicy: Never
+EOF
+```
+
+#### Access the Pod and Test Metrics
+
+Access the pod:
+
+```shell
+kubectl exec -it curl-metrics-catalogd -n olmv1-system -- sh
+```
+
+From the shell use the `TOKEN` value obtained above to check the metrics:
+
+```shell
+curl -v -k -H "Authorization: Bearer <TOKEN>" \
+https://catalogd-service.olmv1-system.svc.cluster.local:7443/metrics
+```
+
+Validate using certificates and token:
+
+```shell
+curl -v --cacert /tmp/cert/ca.crt --cert /tmp/cert/tls.crt --key /tmp/cert/tls.key \
+-H "Authorization: Bearer <TOKEN>" \
+https://catalogd-service.olmv1-system.svc.cluster.local:7443/metrics
+```
+
+---
+
+## Enabling Integration with Prometheus
+
+If using [Prometheus Operator][prometheus-operator], create a `ServiceMonitor` to scrape metrics:
+
+!!! note
+The following manifests are provided as examples. You may need to configure certain settings, such as `serviceMonitorSelector`,  
+to ensure that metrics are properly scraped. This will depend on how Prometheus is configured and, for example, the namespace  
+where the `ServiceMonitor` is applied.
+
+### For Operator-Controller
+
+```shell
+kubectl apply -f - <<EOF
+apiVersion: monitoring.coreos.com/v1
+kind: ServiceMonitor
+metadata:
+  labels:
+    control-plane: operator-controller-controller-manager
+  name: controller-manager-metrics-monitor
+  namespace: olmv1-system
+spec:
+  endpoints:
+    - path: /metrics
+      port: https
+      scheme: https
+      bearerTokenFile: /var/run/secrets/kubernetes.io/serviceaccount/token
+      tlsConfig:
+        insecureSkipVerify: false 
+        serverName: operator-controller-service.olmv1-system.svc
+        ca:
+          secret:
+            name: olmv1-cert
+            key: ca.crt
+        cert:
+          secret:
+            name: olmv1-cert
+            key: tls.crt
+        keySecret:
+          name: olmv1-cert
+          key: tls.key
+  selector:
+    matchLabels:
+      control-plane: operator-controller-controller-manager
+EOF
+```
+
+### For CatalogD
+
+
+```shell
+OLM_SECRET=$(kubectl get secret -n olmv1-system -o jsonpath="{.items[?(@.metadata.name | startswith('catalogd-service-cert'))].metadata.name}")
+```
+
+```shell
+kubectl apply -f - <<EOF
+apiVersion: monitoring.coreos.com/v1
+kind: ServiceMonitor
+metadata:
+  labels:
+    control-plane: catalogd-controller-manager
+  name: catalogd-metrics-monitor
+  namespace: olmv1-system
+spec:
+  endpoints:
+    - path: /metrics
+      port: https
+      scheme: https
+      bearerTokenFile: /var/run/secrets/kubernetes.io/serviceaccount/token
+      tlsConfig:
+        serverName: catalogd-service.olmv1-system.svc
+        insecureSkipVerify: false
+        ca:
+          secret:
+            name: $OLM_SECRET
+            key: ca.crt
+        cert:
+          secret:
+            name: $OLM_SECRET
+            key: tls.crt
+        keySecret:
+          name: $OLM_SECRET
+          key: tls.key
+  selector:
+    matchLabels:
+      control-plane: catalogd-controller-manager
+EOF
+```
+
+[prometheus-operator]: https://github.com/prometheus-operator/kube-prometheus
+[rbac-k8s-docs]: https://kubernetes.io/docs/reference/access-authn-authz/rbac/