HPA

Create an application that has HPA enabled in the ACK console

ACK is integrated with HPA. You can create an application that has HPA enabled in the ACK console. You can enable HPA when you create an application or after the application is created.

Enable HPA when you create an application

1. Log on to the ACK console.
2. In the left-side navigation pane of the ACK console, click Clusters.
3. On the Clusters page, find the cluster that you want to manage and click the name of the cluster or click Details in the Actions column. The details page of the cluster appears.
4. In the left-side navigation pane of the details page, choose Workloads > Deployments.
5. On the Deployments page, click Create from Image.
6. On the Basic Information wizard page, enter a name for your application, set other required parameters, and then click Next.

   Parameter	Description
   Name	The name of the application.
   Replicas	The number of pods that are provisioned for the application. Default value: 2.
   Type	The type of workload. You can select Deployments, StatefulSets, Jobs, CronJobs, or DaemonSets.
   Label	Add a label to the application. The label is used to identify the application.
   Annotations	Add an annotation to the application.
   Synchronize Timezone	Specify whether to synchronize the time zone between nodes and containers.

7. On the Container wizard page, set the container parameters, select an image, and then configure the required computing resources. Click Next. For more information, see Configure containers for an application.
   Note You must configure the required computing resources for the Deployment. Otherwise, you cannot enable HPA.
8. On the Advanced wizard page, find the Access Control section, click Create on the right side of Services, and then set the parameters. For more information, see Configure advanced settings for an application.
9. On the Advanced wizard page, select Enable for HPA and configure the scaling threshold and related settings.
   • Metric: Select CPU Usage or Memory Usage. The selected resource type must be the same as the one that you have specified in the Required Resources field.
   • Condition: Specify the resource usage threshold. HPA triggers scaling activities when the threshold is exceeded.
   • Max. Replicas: Specify the maximum number of pods to which the Deployment can be scaled.
   • Min. Replicas: Specify the minimum number of pods that must run for the Deployment.
10. In the lower-right corner of the Advanced wizard page, click Create. The application is created with HPA enabled.

Enable HPA after an application is created

This example describes how to enable HPA for a stateless application.

1. Log on to the ACK console.
2. In the left-side navigation pane of the ACK console, click Clusters.
3. On the Clusters page, find the cluster that you want to manage and click the name of the cluster or click Details in the Actions column. The details page of the cluster appears.
4. In the left-side navigation pane of the details page, choose Workloads > Deployments.
5. On the Deployments page, click the name of the application that you want to manage.
6. Click the Pod Scaling tab and click Create.
7. In the Create dialog box, configure the HPA settings. For more information about how to set the parameters, see HPA settings in Step 9.
8. Click OK.

Use kubectl to enable HPA

You can also create a Horizontal Pod Autoscaler by using an orchestration template and associate the Horizontal Pod Autoscaler with the Deployment for which you want to enable HPA. Then, you can use kubectl to enable HPA.

In the following example, HPA is enabled for an NGINX application.

1. Create a file named nginx.yml and copy the following content into the file.
   The following code block is a YAML template that is used to create a Deployment:

   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 exactly <image_name:tags>
           ports:
           - containerPort: 80
           resources:
             requests:                         ##To enable HPA, you must set this parameter. 
               cpu: 500m

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

   kubectl create -f nginx.yml

3. Create a Horizontal Pod Autoscaler.
   Use scaleTargetRef to associate the Horizontal Pod Autoscaler with the Deployment named nginx.

   apiVersion: autoscaling/v2beta2
   kind: HorizontalPodAutoscaler
   metadata:
     name: nginx-hpa
   spec:
     scaleTargetRef:
       apiVersion: apps/v1
       kind: Deployment
       name: nginx
     minReplicas: 1
     maxReplicas: 10
     metrics:
     - type: Resource
       resource:
         name: cpu
         target:
           type: Utilization
           averageUtilization: 50
                           

   Note You must configure the requested resources for the pods of the application. Otherwise, the Horizontal Pod Autoscaler cannot be started.
4. Run the kubectl describe hpa name command. The following output is an example of a warning that is returned:

   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. After the Horizontal Pod Autoscaler is created, run the kubectl describe hpa name command.
   If the following output is returned, it indicates that the Horizontal Pod Autoscaler runs as expected:

   Normal SuccessfulRescale 39s horizontal-pod-autoscaler New size: 1; reason: All metrics below target

   If the pod usage of the NGINX application exceeds 50% as specified in the HPA settings, the Horizontal Pod Autoscaler automatically adds pods. If the pod usage of the NGINX application drops below 50%, the Horizontal Pod Autoscaler automatically removes pods.