Container Compute Service:Cron-based container scaling (CronHPA)

Prerequisites

Before you begin, ensure that you have:

• Created an ACS cluster

• Connected to the cluster using kubectl

How CronHPA works

CronHPA is powered by the ack-kubernetes-cronhpa-controller component. It triggers scaling at specific points in time—not across a time window. Each scheduled job fires once at its configured time and sets the replica count to targetSize. CronHPA works with any Kubernetes object that exposes the scale subresource, including Deployments and StatefulSets.

A CronHPA resource looks like this:

apiVersion: autoscaling.alibabacloud.com/v1beta1
kind: CronHorizontalPodAutoscaler
metadata:
  labels:
    controller-tools.k8s.io: "1.0"
  name: cronhpa-sample
  namespace: default
spec:
  scaleTargetRef:
    apiVersion: apps/v1
    kind: Deployment
    name: nginx-deployment-basic
  excludeDates:
  # Exclude November 15th
  - "* * * 15 11 *"
  # Exclude every Friday
  - "* * * * * 5"
  jobs:
  - name: "scale-down"
    schedule: "30 */1 * * * *"
    targetSize: 1
  - name: "scale-up"
    schedule: "0 */1 * * * *"
    targetSize: 3
    runOnce: false

Key fields:

<Seconds> <Minutes> <Hours> <Day of month> <Month> <Day of week>

Install the CronHPA component

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

2. On the Clusters page, click the name of your cluster. In the left navigation pane, click Add-ons.

3. On the Add-ons page, click the Application Management tab. Find ack-kubernetes-cronhpa-controller and click Install. In the dialog box, click OK.

To uninstall CronHPA, see Manage components.

Create a CronHPA scheduled task

Before creating a CronHPA task, ensure that the CronHPA component is running correctly in the cluster and that the application has only one HPA object. For more information about the compatibility policy between CronHPA and HPA, see Use CronHPA with HPA.

Option 1: During application creation

When creating a new application, go to the Advanced Configuration page. In the Scaling Configuration section, select Enable next to Cron-based Scaling.

For instructions on creating an application, see Create a stateless workload (Deployment) or Create a stateful workload (StatefulSet).

If the CronHPA component is not installed, a Click to install message appears. Install the component, then configure the following parameters.

Parameter	Description
Scheduled task name	A unique name for the task.
Target replicas	The number of replicas to scale to at the scheduled time.
Scheduling cycle	The schedule for the task.

Add or modify a scheduled task

1. Follow the steps in Option 2: For an existing application to reach the Container Scaling tab.

2. In the Cron-based Scaling (CronHPA) section, find the task and click Add or Edit Task in the Actions column.

3. In the Edit dialog box, click Add Task to add a new task, or click an existing task to modify it. Click OK to save.

   To delete a task, click the delete icon in the upper-right corner of the task card in the Edit dialog box, then click OK.

   

Use CronHPA with HPA

CronHPA and HPA both act on workloads, and running both on the same workload without coordination causes conflicts—the later operation overwrites the earlier one.

To avoid this, set CronHPA's scaleTargetRef to the HPA object instead of the workload directly. CronHPA then reads the HPA's state before acting, and adjusts the HPA's minReplicas or maxReplicas rather than writing to the workload directly.

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

apiVersion: autoscaling/v2
kind: HorizontalPodAutoscaler
metadata:
  name: nginx-deployment-basic-hpa
spec:
  scaleTargetRef:
    apiVersion: apps/v1
    kind: Deployment
    name: nginx-deployment-basic
  minReplicas: 4
  maxReplicas: 10
  metrics:
  - type: Resource
    resource:
      name: cpu
      target:
        type: Utilization
        averageUtilization: 50

What's next

• Horizontal pod autoscaling (HPA)

• kubernetes-cronhpa-controller

• Manage components