×

You can export custom application metrics for the horizontal pod autoscaler.

Prometheus Adapter is a Technology Preview feature only. Technology Preview features are not supported with Red Hat production service level agreements (SLAs) and might not be functionally complete. Red Hat does not recommend using them in production. These features provide early access to upcoming product features, enabling customers to test functionality and provide feedback during the development process.

For more information about the support scope of Red Hat Technology Preview features, see https://access.redhat.com/support/offerings/techpreview/.

Exposing custom application metrics for horizontal pod autoscaling

You can use the prometheus-adapter resource to expose custom application metrics for the horizontal pod autoscaler.

Prerequisites
  • You have a custom Prometheus instance installed as a Prometheus pod managed by a deployment or StatefulSet object but not by a Prometheus custom resource (CR).

  • You have installed the custom Prometheus instance in a user-defined custom-prometheus project.

    Custom Prometheus instances and the Prometheus Operator installed through Operator Lifecycle Manager (OLM) are not compatible with user-defined monitoring if it is enabled. Therefore, custom Prometheus instances that are installed as a Prometheus custom resource (CR) managed by the OLM Prometheus Operator are not supported in OKD.

  • You have deployed an application and a service in a user-defined project. In this example, it is presumed that the application and its service monitor were installed in a user-defined custom-prometheus project.

  • You have installed the OpenShift CLI (oc).

Procedure
  1. Create a YAML file for your configuration. In this example, the file is called deploy.yaml.

  2. Add configuration details for creating the service account, roles, and role bindings for prometheus-adapter:

    kind: ServiceAccount
    apiVersion: v1
    metadata:
      name: custom-metrics-apiserver
      namespace: custom-prometheus
    ---
    apiVersion: rbac.authorization.k8s.io/v1
    kind: ClusterRole
    metadata:
      name: custom-metrics-server-resources
    rules:
    - apiGroups:
      - custom.metrics.k8s.io
      resources: ["*"]
      verbs: ["*"]
    ---
    apiVersion: rbac.authorization.k8s.io/v1
    kind: ClusterRole
    metadata:
      name: custom-metrics-resource-reader
    rules:
    - apiGroups:
      - ""
      resources:
      - namespaces
      - pods
      - services
      verbs:
      - get
      - list
    ---
    apiVersion: rbac.authorization.k8s.io/v1
    kind: ClusterRoleBinding
    metadata:
      name: custom-metrics:system:auth-delegator
    roleRef:
      apiGroup: rbac.authorization.k8s.io
      kind: ClusterRole
      name: system:auth-delegator
    subjects:
    - kind: ServiceAccount
      name: custom-metrics-apiserver
      namespace: custom-prometheus
    ---
    apiVersion: rbac.authorization.k8s.io/v1
    kind: RoleBinding
    metadata:
      name: custom-metrics-auth-reader
      namespace: kube-system
    roleRef:
      apiGroup: rbac.authorization.k8s.io
      kind: Role
      name: extension-apiserver-authentication-reader
    subjects:
    - kind: ServiceAccount
      name: custom-metrics-apiserver
      namespace: custom-prometheus
    ---
    apiVersion: rbac.authorization.k8s.io/v1
    kind: ClusterRoleBinding
    metadata:
      name: custom-metrics-resource-reader
    roleRef:
      apiGroup: rbac.authorization.k8s.io
      kind: ClusterRole
      name: custom-metrics-resource-reader
    subjects:
    - kind: ServiceAccount
      name: custom-metrics-apiserver
      namespace: custom-prometheus
    ---
    apiVersion: rbac.authorization.k8s.io/v1
    kind: ClusterRoleBinding
    metadata:
      name: hpa-controller-custom-metrics
    roleRef:
      apiGroup: rbac.authorization.k8s.io
      kind: ClusterRole
      name: custom-metrics-server-resources
    subjects:
    - kind: ServiceAccount
      name: horizontal-pod-autoscaler
      namespace: kube-system
    ---
  3. Add configuration details for the custom metrics for prometheus-adapter:

    apiVersion: v1
    kind: ConfigMap
    metadata:
      name: adapter-config
      namespace: custom-prometheus
    data:
      config.yaml: |
        rules:
        - seriesQuery: 'http_requests_total{namespace!="",pod!=""}' (1)
          resources:
            overrides:
              namespace: {resource: "namespace"}
              pod: {resource: "pod"}
              service: {resource: "service"}
          name:
            matches: "^(.*)_total"
            as: "${1}_per_second" (2)
          metricsQuery: 'sum(rate(<<.Series>>{<<.LabelMatchers>>}[2m])) by (<<.GroupBy>>)'
    ---
    1 Specifies the chosen metric to be the number of HTTP requests.
    2 Specifies the frequency for the metric.
  4. Add configuration details for registering prometheus-adapter as an API service:

    apiVersion: v1
    kind: Service
    metadata:
      annotations:
        service.beta.openshift.io/serving-cert-secret-name: prometheus-adapter-tls
      labels:
        name: prometheus-adapter
      name: prometheus-adapter
      namespace: custom-prometheus
    spec:
      ports:
      - name: https
        port: 443
        targetPort: 6443
      selector:
        app: prometheus-adapter
      type: ClusterIP
    ---
    apiVersion: apiregistration.k8s.io/v1beta1
    kind: APIService
    metadata:
      name: v1beta1.custom.metrics.k8s.io
    spec:
      service:
        name: prometheus-adapter
        namespace: custom-prometheus
      group: custom.metrics.k8s.io
      version: v1beta1
      insecureSkipTLSVerify: true
      groupPriorityMinimum: 100
      versionPriority: 100
    ---
  5. List the Prometheus Adapter image:

    $ oc get -n openshift-monitoring deploy/prometheus-adapter -o jsonpath="{..image}"
  6. Add configuration details for deploying prometheus-adapter:

    apiVersion: apps/v1
    kind: Deployment
    metadata:
      labels:
        app: prometheus-adapter
      name: prometheus-adapter
      namespace: custom-prometheus
    spec:
      replicas: 1
      selector:
        matchLabels:
          app: prometheus-adapter
      template:
        metadata:
          labels:
            app: prometheus-adapter
          name: prometheus-adapter
        spec:
          serviceAccountName: custom-metrics-apiserver
          containers:
          - name: prometheus-adapter
            image: quay.io/openshift-release-dev/ocp-v4.0-art-dev@sha256:a46915a206cd7d97f240687c618dd59e8848fcc3a0f51e281f3384153a12c3e0 (1)
            args:
            - --secure-port=6443
            - --tls-cert-file=/var/run/serving-cert/tls.crt
            - --tls-private-key-file=/var/run/serving-cert/tls.key
            - --logtostderr=true
            - --prometheus-url=http://prometheus-operated.default.svc:9090/
            - --metrics-relist-interval=1m
            - --v=4
            - --config=/etc/adapter/config.yaml
            ports:
            - containerPort: 6443
            volumeMounts:
            - mountPath: /var/run/serving-cert
              name: volume-serving-cert
              readOnly: true
            - mountPath: /etc/adapter/
              name: config
              readOnly: true
            - mountPath: /tmp
              name: tmp-vol
          volumes:
          - name: volume-serving-cert
            secret:
              secretName: prometheus-adapter-tls
          - name: config
            configMap:
              name: adapter-config
          - name: tmp-vol
            emptyDir: {}
    1 Specifies the Prometheus Adapter image found in the previous step.
  7. Apply the configuration to the cluster:

    $ oc apply -f deploy.yaml
    Example output
    serviceaccount/custom-metrics-apiserver created
    clusterrole.rbac.authorization.k8s.io/custom-metrics-server-resources created
    clusterrole.rbac.authorization.k8s.io/custom-metrics-resource-reader created
    clusterrolebinding.rbac.authorization.k8s.io/custom-metrics:system:auth-delegator created
    rolebinding.rbac.authorization.k8s.io/custom-metrics-auth-reader created
    clusterrolebinding.rbac.authorization.k8s.io/custom-metrics-resource-reader created
    clusterrolebinding.rbac.authorization.k8s.io/hpa-controller-custom-metrics created
    configmap/adapter-config created
    service/prometheus-adapter created
    apiservice.apiregistration.k8s.io/v1.custom.metrics.k8s.io created
    deployment.apps/prometheus-adapter created
  8. Verify that the prometheus-adapter pod in your user-defined project is in a Running state. In this example the project is custom-prometheus:

    $ oc -n custom-prometheus get pods prometheus-adapter-<string>
  9. The metrics for the application are now exposed and they can be used to configure horizontal pod autoscaling.