Container Service for Kubernetes:Implement horizontal pod autoscaling

You can enable the Horizontal Pod Autoscaler (HPA) feature to automatically scale pods based on CPU utilization, memory usage, or other metrics. HPA can quickly scale out replicated pods to handle heavy stress when the workloads surge and scale in appropriately to save resources when the workloads decrease. The entire process is automated and requires no human intervention. It is ideal for businesses with large fluctuations in service, large numbers of services, and frequent scaling requirements, such as e-commerce services, online education, and financial services.

Create an application that has HPA enabled by using kubectl

You can also create an HPA by using an orchestration template and associate the HPA with the Deployment for which you want to enable HPA. Then, you can run kubectl commands to enable HPA. We recommend that you create only one application that has HPA enabled for a workload. In the following example, HPA is enabled for an NGINX application.

1. Create a file named nginx.yml and copy the following content to the file.

   Important

   You must configure the request resources required by the application. Otherwise, you cannot enable HPA.

   apiVersion: apps/v1 
   kind: Deployment
   metadata:
     name: nginx
     labels:
       app: nginx
   spec:
     replicas: 2
     selector:
       matchLabels:
         app: nginx  
     template:
       metadata:
         labels:
           app: nginx
       spec:
         containers:
         - name: nginx
           image: nginx:1.7.9 # Replace it with your actual <image_name:tags>.
           ports:
           - containerPort: 80
           resources:
             requests:                         # This parameter is required for running the HPA.
               cpu: 500m

2. Run the following command to create an NGINX application:

   kubectl apply -f nginx.yml

3. Create a file named hpa.yml and copy the following content to the file to create an HPA.

   Use the scaleTargetRef parameter to associate the HPA with the nginx Deployment and trigger scaling operations when the average CPU utilization of all containers in the pod reaches 50%.

   YAML template for clusters whose Kubernetes versions are 1.24 and later

   apiVersion: autoscaling/v2
   kind: HorizontalPodAutoscaler
   metadata:
     name: nginx-hpa
   spec:
     scaleTargetRef:
       apiVersion: apps/v1
       kind: Deployment
       name: nginx
     minReplicas: 1  # The minimum number of containers that must run for the Deployment. The value of this parameter must be an integer greater than or equal to 1.
     maxReplicas: 10  # The maximum number of containers to which the Deployment can be scaled. The value of this parameter must be greater than minReplicas.
     metrics:
     - type: Resource
       resource:
         name: cpu
         target:
           type: Utilization
           averageUtilization: 50 # The average utilization of the target resource, which is the ratio of the average value of resource usage to its request amount.
                  

   YAML template for clusters whose Kubernetes versions are earlier than 1.24

   apiVersion: autoscaling/v2beta2
   kind: HorizontalPodAutoscaler
   metadata:
     name: nginx-hpa
   spec:
     scaleTargetRef:
       apiVersion: apps/v1
       kind: Deployment
       name: nginx
     minReplicas: 1  # Must be an integer greater than or equal to 1.
     maxReplicas: 10  # Must be greater than minReplicas.
     metrics:
     - type: Resource
       resource:
         name: cpu
         target:
           type: Utilization
           averageUtilization: 50
                  

   If you need to specify both CPU and memory metrics, you can specify both cpu and memory types of resources under the metrics field instead of creating two HPAs. If HPA detects that any one of the metrics reaches the scaling threshold, it will perform scaling operations.

   metrics:
     - type: Resource
       resource:
         name: cpu
         target:
           type: Utilization
           averageUtilization: 50
     - type: Resource
       resource:
         name: memory
         target:
           type: Utilization
           averageUtilization: 50

4. Run the following command to create an HPA:

   kubectl apply -f hpa.yml

   At this point, run the kubectl describe hpa <HPA name> command, a warning similar to the following output is returned, indicating that the HPA is still being deployed. The HPA name in this example is nginx-hpa.yml. You can run the kubectl get hpa command to check the status of the HPA.

   Warning  FailedGetResourceMetric       2m (x6 over 4m)  horizontal-pod-autoscaler  missing request for cpu on container nginx in pod default/nginx-deployment-basic-75675f5897-mqzs7
   
   Warning  FailedComputeMetricsReplicas  2m (x6 over 4m)  horizontal-pod-autoscaler  failed to get cpu utilization: missing request for cpu on container nginx in pod default/nginx-deployment-basic-75675f5

5. Wait for the HPA to be created and the pod to reach the scaling condition, which is when the pod CPU utilization of NGINX exceeds 50% in this example. Then, run the kubectl describe hpa <HPA name> command again to check the horizontal scaling status.

   If the following output is returned, the HPA is running as expected:

   Type    Reason             Age   From                       Message
     ----    ------             ----  ----                       -------
     Normal  SuccessfulRescale  5m6s  horizontal-pod-autoscaler  New size: 1; reason: All metrics below target