Container Compute Service:Use Knative and AHPA to configure scheduled auto scaling

Step 1: Use AHPA to configure metrics for auto scaling

Create an AHPA ConfigMap based on the following YAML content and deploy AHPA in the ACS cluster.

apiVersion: autoscaling.alibabacloud.com/v1beta1
kind: AdvancedHorizontalPodAutoscalerTemplate
metadata:
  name: ahpa-demo
spec:
  metrics:
  - type: Resource
    resource:
      name: rps
      target:
        type: Utilization
        averageUtilization: 10 # The RPS threshold is set to 10. 
  maxReplicas: 50 # The maximum number of replicated pods is set to 50. 
  minReplicas: 0 # The minimum number of replicated pods is set to 0. 
  prediction:
    quantile: 95 # The confidence level of prediction is set to 95%. 
    scaleUpForward: 180 # The time range of forward prediction is set to 180 seconds. 
# The number of replicated pods is limited by the maximum number of replicated pods and the minimum number of replicated pods defined by AHPA from 00:00:00 on June 1, 2023 to 00:00:00 on June 1, 2123. 
  instanceBounds:
  - startTime: "2023-06-01 00:00:00"
    endTime: "2123-06-01 00:00:00"
    bounds:
# The minimum number of replicated pods is 0 and the maximum number of replicated pods is 50 from 0 am to 6 am. 
    - cron: '* 0-6 ?  * *'
      maxReplicas: 50
      minReplicas: 0
# The minimum number of replicated pods is 5 and the maximum number of replicated pods is 50 from 7 am to 9 am. 
    - cron: '* 7-9 ?  * *'
      maxReplicas: 50
      minReplicas: 5
# The minimum number of replicated pods is 10 and the maximum number of replicated pods is 50 from 10 am to 4 pm. 
    - cron: '* 10-16 ?  * *'
      maxReplicas: 50
      minReplicas: 10
# The minimum number of replicated pods is 2 and the maximum number of replicated pods is 50 from 5 pm to 11 pm. 
    - cron: '* 17-23 ?  * *'
      maxReplicas: 50
      minReplicas: 2

Fields used in cron expressions

The fields of a cron expression are described as follows. For more information, see Cron scheduled tasks.

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 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 for the Service

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

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

3. On the Knative page, click the Services tab. Select default from the Namespace drop-down list. Click Create from Template, paste the following YAML template into the editor, and click Create. This creates 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 plug-in. 
           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 of the Service, which will be used in Step 3: Access the Service.

   On the Services tab, you can find the gateway address (for example, alb-xxx.ncs.com) in the Access Gateway section. In the service list, the Default Domain Name column shows the service domain name (for example, helloworld-go.default.example.com). To access the Service, send a request to the gateway address with the Host header set to the service's default domain name.

Step 3: Access the Service

1. 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 results:

   Hello Knative!

Step 4 (Optional): Verify scheduled auto scaling

On the Knative Monitoring Dashboards page, you can view the scaling trends of Knative service instances. For more information about the Knative Monitoring Dashboard, see View the Knative Service Monitoring Dashboard.

References

You can configure auto scaling based on the number of concurrent pod requests and RPS configurations. For more information, see Enable auto scaling to withstand traffic fluctuations.