Container Service for Kubernetes:Use Knative and AHPA to implement scheduled auto scaling

Step 1: Configure AHPA metrics for auto scaling

Create an AHPA configuration file and deploy it to the cluster.

apiVersion: autoscaling.alibabacloud.com/v1beta1
kind: AdvancedHorizontalPodAutoscalerTemplate
metadata:
  name: ahpa-demo
spec:
  metrics:
  - type: Resource
    resource:
      name: rps
      target:
        type: Utilization
        averageUtilization: 10 # RPS threshold set to 10.
  maxReplicas: 50 # Maximum number of replicas set to 50.
  minReplicas: 0 # Minimum number of replicas set to 0.
  prediction:
    quantile: 95 # Prediction confidence level set to 95%.
    scaleUpForward: 180 # Forward prediction time range set to 180 seconds.
# Replica counts are bounded by the AHPA-defined max and min from 2023-06-01 to 2123-06-01.
  instanceBounds:
  - startTime: "2023-06-01 00:00:00"
    endTime: "2123-06-01 00:00:00"
    bounds:
# 0:00 AM - 6:00 AM: min 0, max 50
    - cron: '* 0-6 ? * *'
      maxReplicas: 50
      minReplicas: 0
# 7:00 AM - 9:00 AM: min 5, max 50
    - cron: '* 7-9 ? * *'
      maxReplicas: 50
      minReplicas: 5
# 10:00 AM - 4:00 PM: min 10, max 50
    - cron: '* 10-16 ? * *'
      maxReplicas: 50
      minReplicas: 10
# 5:00 PM - 11:00 PM: min 2, max 50
    - cron: '* 17-23 ? * *'
      maxReplicas: 50
      minReplicas: 2

The following table describes the AHPA parameters.

Cron expression fields

The following table describes the fields in a cron expression. For more information, see Cron expressions.

Special characters used in cron expressions:

• An asterisk (*) indicates any value. For example, * indicates any minute or hour.

• A forward slash (/) indicates the step size. For example, /5 indicates every five time units.

• Commas (,) are used as delimiters. For example, 1,3,5 indicates values 1, 3, and 5.

• Hyphens (-) are used in value ranges. For example, 1-5 indicates values 1 to 5.

• Question marks (?) are used only in the Day of month and Day of week fields to indicate variable values.

Step 2: Create a Knative Service and enable AHPA

After you deploy AHPA, you can use it through a Knative Service.

1. Log on to the Container Service Management Console . In the navigation pane on the left, click Clusters.

2. On the Clusters page, click the name of your cluster. In the navigation pane on the left, click Applications > Knative.

3. On the Services tab of the Knative page, set Namespace to default, click Create from Template, copy the following YAML content to the editor, and then click Create to create a Service named helloworld-go-demo.

   apiVersion: serving.knative.dev/v1
   kind: Service
   metadata:
     name: helloworld-go-demo
   spec:
     template:
       metadata:
         annotations:
           autoscaling.knative.dev/class: ahpa.autoscaling.knative.dev # Specify the AHPA plugin.
           autoscaling.knative.dev.alibabacloud/ahpa-template: "ahpa-demo" # If you modify the AHPA template parameter, the corresponding revision is also updated.
       spec:
         containers:
         - image: registry.cn-hangzhou.aliyuncs.com/knative-sample/helloworld-go:73fbdd56
           env:
           - name: TARGET
             value: "Knative"

   After the Service is created, record the gateway address and domain name. You need them in Step 3.

   

Step 3: Access the Service

Run the following command to access the Service:

# helloworld-go-demo.default.example.com is the default domain name of the Service.
# alb-i5lagvip6fga******.cn-shenzhen.alb.aliyuncs.com is the gateway address of the Service.
curl -H "Host: helloworld-go-demo.default.example.com" http://alb-i5lagvip6fga******.cn-shenzhen.alb.aliyuncs.com

Expected output:

Hello Knative!

Step 4 (optional): Verify scheduled scaling

On the Monitoring Dashboards of Knative, you can view the trends of pod scaling for the Knative Service. For more information about the Knative dashboard, see View the Knative monitoring dashboard.

References

For information about configuring auto scaling based on concurrent pod requests and RPS, see Enable auto scaling to withstand traffic fluctuations.