This section describes how to manually install HPAs for clusters created with Rancher prior to v2.0.7. This section also describes how to configure your HPA to scale up or down, and how to assign roles to your HPA.

Before you can use HPA in your Kubernetes cluster, you must fulfill some requirements.

Requirements

Be sure that your Kubernetes cluster services are running with these flags at minimum:

  • kube-api: requestheader-client-ca-file
  • kubelet: read-only-port at 10255
  • kube-controller: Optional, just needed if distinct values than default are required.

    • horizontal-pod-autoscaler-downscale-delay: "5m0s"
    • horizontal-pod-autoscaler-upscale-delay: "3m0s"
    • horizontal-pod-autoscaler-sync-period: "30s"

For an RKE Kubernetes cluster definition, add this snippet in the services section. To add this snippet using the Rancher v2.0 UI, open the Clusters view and select Ellipsis (…) > Edit for the cluster in which you want to use HPA. Then, from Cluster Options, click Edit as YAML. Add the following snippet to the services section:

services:
...
  kube-api:
    extra_args:
      requestheader-client-ca-file: "/etc/kubernetes/ssl/kube-ca.pem"
  kube-controller:
    extra_args:
      horizontal-pod-autoscaler-downscale-delay: "5m0s"
      horizontal-pod-autoscaler-upscale-delay: "1m0s"
      horizontal-pod-autoscaler-sync-period: "30s"
  kubelet:
    extra_args:
      read-only-port: 10255

Once the Kubernetes cluster is configured and deployed, you can deploy metrics services.

Note: kubectl command samples in the sections that follow were tested in a cluster running Rancher v2.0.6 and Kubernetes v1.10.1.

Configuring HPA to Scale Using Resource Metrics

To create HPA resources based on resource metrics such as CPU and memory use, you need to deploy the metrics-server package in the kube-system namespace of your Kubernetes cluster. This deployment allows HPA to consume the metrics.k8s.io API.

Prerequisite: You must be running kubectl 1.8 or later.

  1. Connect to your Kubernetes cluster using kubectl.

  2. Clone the GitHub metrics-server repo:

    # git clone https://github.com/kubernetes-incubator/metrics-server
    
  3. Install the metrics-server package.

    # kubectl create -f metrics-server/deploy/1.8+/
    
  4. Check that metrics-server is running properly. Check the service pod and logs in the kube-system namespace.

    1. Check the service pod for a status of running. Enter the following command:

      # kubectl get pods -n kube-system
      

      Then check for the status of running.

      NAME                                  READY     STATUS    RESTARTS   AGE
      ...
      metrics-server-6fbfb84cdd-t2fk9       1/1       Running   0          8h
      ...
      
    2. Check the service logs for service availability. Enter the following command:

      # kubectl -n kube-system logs metrics-server-6fbfb84cdd-t2fk9
      

      Then review the log to confirm that the metrics-server package is running.

      I0723 08:09:56.193136       1 heapster.go:71] /metrics-server --source=kubernetes.summary_api:''
      I0723 08:09:56.193574       1 heapster.go:72] Metrics Server version v0.2.1
      I0723 08:09:56.194480       1 configs.go:61] Using Kubernetes client with master "https://10.43.0.1:443" and version
      I0723 08:09:56.194501       1 configs.go:62] Using kubelet port 10255
      I0723 08:09:56.198612       1 heapster.go:128] Starting with Metric Sink
      I0723 08:09:56.780114       1 serving.go:308] Generated self-signed cert (apiserver.local.config/certificates/apiserver.crt, apiserver.local.config/certificates/apiserver.key)
      I0723 08:09:57.391518       1 heapster.go:101] Starting Heapster API server...
      [restful] 2018/07/23 08:09:57 log.go:33: [restful/swagger] listing is available at https:///swaggerapi
      [restful] 2018/07/23 08:09:57 log.go:33: [restful/swagger] https:///swaggerui/ is mapped to folder /swagger-ui/
      I0723 08:09:57.394080       1 serve.go:85] Serving securely on 0.0.0.0:443
      

  5. Check that the metrics api is accessible from kubectl.

    • If you are accessing the cluster through Rancher, enter your Server URL in the kubectl config in the following format: https://<RANCHER_URL>/k8s/clusters/<CLUSTER_ID>. Add the suffix /k8s/clusters/<CLUSTER_ID> to API path.

      # kubectl get --raw /k8s/clusters/<CLUSTER_ID>/apis/metrics.k8s.io/v1beta1
      

      If the API is working correctly, you should receive output similar to the output below.

      {"kind":"APIResourceList","apiVersion":"v1","groupVersion":"metrics.k8s.io/v1beta1","resources":[{"name":"nodes","singularName":"","namespaced":false,"kind":"NodeMetrics","verbs":["get","list"]},{"name":"pods","singularName":"","namespaced":true,"kind":"PodMetrics","verbs":["get","list"]}]}
      
    • If you are accessing the cluster directly, enter your Server URL in the kubectl config in the following format: https://<K8s_URL>:6443.

      # kubectl get --raw /apis/metrics.k8s.io/v1beta1
      

      If the API is working correctly, you should receive output similar to the output below.

      {"kind":"APIResourceList","apiVersion":"v1","groupVersion":"metrics.k8s.io/v1beta1","resources":[{"name":"nodes","singularName":"","namespaced":false,"kind":"NodeMetrics","verbs":["get","list"]},{"name":"pods","singularName":"","namespaced":true,"kind":"PodMetrics","verbs":["get","list"]}]}
      

Assigning Additional Required Roles to Your HPA

By default, HPA reads resource and custom metrics with the user system:anonymous. Assign system:anonymous to view-resource-metrics and view-custom-metrics in the ClusterRole and ClusterRoleBindings manifests. These roles are used to access metrics.

To do it, follow these steps:

  1. Configure kubectl to connect to your cluster.

  2. Copy the ClusterRole and ClusterRoleBinding manifest for the type of metrics you’re using for your HPA.

        apiVersion: rbac.authorization.k8s.io/v1
        kind: ClusterRole
        metadata:
          name: view-resource-metrics
        rules:
        - apiGroups:
            - metrics.k8s.io
          resources:
            - pods
            - nodes
          verbs:
            - get
            - list
            - watch
        ---
        apiVersion: rbac.authorization.k8s.io/v1
        kind: ClusterRoleBinding
        metadata:
          name: view-resource-metrics
        roleRef:
          apiGroup: rbac.authorization.k8s.io
          kind: ClusterRole
          name: view-resource-metrics
        subjects:
          - apiGroup: rbac.authorization.k8s.io
            kind: User
            name: system:anonymous
    
      apiVersion: rbac.authorization.k8s.io/v1
      kind: ClusterRole
      metadata:
        name: view-custom-metrics
      rules:
      - apiGroups:
          - custom.metrics.k8s.io
        resources:
          - "*"
        verbs:
          - get
          - list
          - watch
      ---
      apiVersion: rbac.authorization.k8s.io/v1
      kind: ClusterRoleBinding
      metadata:
        name: view-custom-metrics
      roleRef:
        apiGroup: rbac.authorization.k8s.io
        kind: ClusterRole
        name: view-custom-metrics
      subjects:
        - apiGroup: rbac.authorization.k8s.io
          kind: User
          name: system:anonymous
    

  3. Create them in your cluster using one of the follow commands, depending on the metrics you’re using.

    # kubectl create -f <RESOURCE_METRICS_MANIFEST>
    # kubectl create -f <CUSTOM_METRICS_MANIFEST>