Container Compute Service:CronHPA

Install the CronHPA controller

You can install the CronHPA controller ack-kubernetes-cronhpa-controller by using one of the following methods.

1. Log on to the ACS console. In the left-side navigation pane, click Clusters.

2. On the Clusters page, find the cluster that you want to manage and click its ID. In the left-side navigation pane of the cluster details page, choose Operations > Add-ons.

3. On the Add-ons page, click the Manage Applications tab, find ack-kubernetes-cronhpa-controller, and then click Install. In the message that appears, click OK.

Create CronHPA jobs

Before you create and run CronHPA jobs for your application, make sure that the CronHPA controller runs as normal in your cluster and only one HPA task is created for your application. For more information about how to enable CronHPA and HPA to interact without conflicts, see Enable CronHPA and HPA to interact without conflicts. You can create CronHPA jobs by using one of the following methods:

Method 1: Create CronHPA jobs when you create an application

Method 2: Create CronHPA jobs for an existing application

The following example demonstrates how to create a CronHPA job for an existing application. A stateless application is used in this example.

1. Log on to the ACS console. In the left-side navigation pane, click Clusters.

2. On the Clusters page, find the cluster that you want to manage and click its ID. In the left-side navigation pane of the cluster details page, choose Workloads > Deployments.

3. On the Deployments page, find the application that you want to manage and click Details in the Actions column.

4. Click the Pod Scaling tab and configure CronHPA jobs.

   • If the CronHPA controller is not installed, the Install button appears on the page. Click Install and perform the following steps.

   • If the CronHPA controller is installed, perform the following steps.

5. Click Create on the right side of CronHPA. In the Create dialog box, configure the parameters of the CronHPA job.

   

   The following table describes the parameters.

   Parameter	Description
   Job Name	Enter a name for the CronHPA job. The name of each CronHPA job must be unique.
   Desired Number of Replicas	Replicated pods are scaled to the desired number at the scheduled time.
   Scaling Schedule	Set the scaling schedule. For more information about how to set the scaling schedule for a CronHPA job, see predefined-schedules.

Create or modify CronHPA jobs

1. Go to the Pod Scaling tab by performing the steps that are described in the preceding Create CronHPA jobs section.

2. On the Pod Scaling tab, find the CronHPA job that you created in the CronHPA section and click Add or Modify Job in the Actions column.

3. In the Edit dialog box, click Add Job to create CronHPA jobs. You can also modify an existing CronHPA job. Then, click OK.

   

   Note

   To delete CronHPA jobs, perform the steps described in the following figure. In the Edit dialog box, click the delete icon in the upper-right corner of the job that you want to delete. Then, click OK.

Templates of CronHPA and HPA

Enable CronHPA and HPA to interact without conflicts

CronHPA and HPA take effect on workloads, such as Deployments or StatefulSets. If you use CronHPA and HPA to scale a workload at the same time, conflicts may occur. To resolve the conflicts, CronHPA allows you to use HPA as the object to be scaled, which is compatible with the features of HPA.

If both CronHPA and HPA are deployed, CronHPA and HPA may scale pods for the same application that is specified by scaleTargetRef. CronHPA and HPA are independent and unaware of each other. As a result, the CronHPA controller and the HPA controller separately scale pods for the application. The later scaling activity overwrites the earlier activity.

Solution

To avoid the conflict, CronHPA needs only to detect the status of HPA. ACS modifies the CronHPA configuration by setting scaleTargetRef to HPA instead of the target workload. When CronHPA performs scaling operations, it first finds the application that is specified by scaleTargetRef in the HPA configuration, and then makes adjustments to the workload. This helps avoid overriding the configuration and ensures consistency and predictability in scaling operations.

apiVersion: autoscaling.alibabacloud.com/v1beta1
kind: CronHorizontalPodAutoscaler
metadata:
  labels:
    controller-tools.k8s.io: "1.0"
  name: cronhpa-sample
spec:
   scaleTargetRef:
      apiVersion: autoscaling/v1
      kind: HorizontalPodAutoscaler
      name:  nginx-deployment-basic-hpa
   jobs:
   - name: "scale-down"
     schedule: "30 */1 * * * *"
     targetSize: 1
     runOnce: false
   - name: "scale-up"
     schedule: "0 */1 * * * *"
     targetSize: 3
     runOnce: false

After you deploy the preceding YAML template, CronHPA is aware of the values of spec.minReplicas, spec.maxReplicas, and status.desiredReplicas in the HPA configuration. CronHPA is also aware of the value of Replicas that is specified by spec.scaleTargetRef in the HPA configuration. CronHPA can detect the status of HPA by modifying the HPA configurations. CronHPA compares the desired number of pods with the current number of pods and then determines whether to trigger scaling activities and change the maximum number of pods in the HPA configuration. CronHPA also compares the desired number of pods with the maximum and minimum numbers of pods that are specified in the HPA configuration and then determines whether to change the minimum number of pods in the HPA configuration.

CronHPA does not directly change the number of pods for the Deployment. Instead, CronHPA triggers HPA to scale the pods. This resolves the conflict between CronHPA and HPA.