This guide describes the built-in monitoring support provided by the Operator SDK using the Prometheus Operator and details usage for Operator authors.

Prometheus Operator support

Prometheus is an open-source systems monitoring and alerting toolkit. The Prometheus Operator creates, configures, and manages Prometheus clusters running on Kubernetes-based clusters, such as OpenShift Container Platform.

Helper functions exist in the Operator SDK by default to automatically set up metrics in any generated Go-based Operator for use on clusters where the Prometheus Operator is deployed.

Exposing custom metrics

As an Operator author, you can publish custom metrics by using the global Prometheus registry from the controller-runtime/pkg/metrics library.

  • Go-based Operator generated using the Operator SDK

  • Prometheus Operator (deployed by default on OpenShift Container Platform clusters)

  1. In your Operator SDK project, uncomment the following line in the config/default/kustomization.yaml file:

  2. Create a custom controller class to publish additional metrics from the Operator. The following example declares the widgets and widgetFailures collectors as global variables, and then registers them with the init() function in the controller’s package:

    controllers/memcached_controller_test_metrics.go file
    package controllers
    import (
    var (
        widgets = prometheus.NewCounter(
                Name: "widgets_total",
                Help: "Number of widgets processed",
        widgetFailures = prometheus.NewCounter(
                Name: "widget_failures_total",
                Help: "Number of failed widgets",
    func init() {
        // Register custom metrics with the global prometheus registry
        metrics.Registry.MustRegister(widgets, widgetFailures)
  3. Record to these collectors from any part of the reconcile loop in the main controller class, which determines the business logic for the metric:

    controllers/memcached_controller.go file
    func (r *MemcachedReconciler) Reconcile(ctx context.Context, req ctrl.Request) (ctrl.Result, error) {
    	// Add metrics
    	return ctrl.Result{}, nil
  4. Build and push the Operator:

    $ make docker-build docker-push IMG=<registry>/<user>/<image_name>:<tag>
  5. Deploy the Operator:

    $ make deploy IMG=<registry>/<user>/<image_name>:<tag>
  6. Create role and role binding definitions to allow the service monitor of the Operator to be scraped by the Prometheus instance of the OpenShift Container Platform cluster.

    Roles must be assigned so that service accounts have the permissions to scrape the metrics of the namespace:

    config/prometheus/role.yaml role
    apiVersion: rbac.authorization.k8s.io/v1
    kind: ClusterRole
      name: prometheus-k8s-role
      namespace: <operator_namespace>
      - apiGroups:
          - ""
          - endpoints
          - pods
          - services
          - nodes
          - secrets
          - get
          - list
          - watch
    config/prometheus/rolebinding.yaml role binding
    apiVersion: rbac.authorization.k8s.io/v1
    kind: ClusterRoleBinding
      name: prometheus-k8s-rolebinding
      namespace: memcached-operator-system
      apiGroup: rbac.authorization.k8s.io
      kind: ClusterRole
      name: prometheus-k8s-role
      - kind: ServiceAccount
        name: prometheus-k8s
        namespace: openshift-monitoring
  7. Apply the roles and role bindings for the deployed Operator:

    $ oc apply -f config/prometheus/role.yaml
    $ oc apply -f config/prometheus/rolebinding.yaml
  8. Set the labels for the namespace that you want to scrape, which enables OpenShift cluster monitoring for that namespace:

    $ oc label namespace <operator_namespace> openshift.io/cluster-monitoring="true"
  • Query and view the metrics in the OpenShift Container Platform web console. You can use the names that were set in the custom controller class, for example widgets_total and widget_failures_total.