Setup Horizontal Pod Autoscaling (HPA)

In Kubernetes, a HorizontalPodAutoscaler automatically updates a workload resource (such as a Deployment or StatefulSet), to automatically scale the workload to match demand.

Horizontal scaling means that the response to increased load is to deploy more Pods. This is different from vertical scaling, which for Kubernetes would mean assigning more resources (for example: memory or CPU) to the Pods that are already running for the workload.

If the load decreases, and the number of Pods is above the configured minimum, the HorizontalPodAutoscaler instructs the workload resource (the Deployment, StatefulSet, or other similar resource) to scale back down.

1. Setup HPA

Inspect the ~/workshop/k3s/hpa.yaml file and validate the contents using the following command:

cat ~/workshop/k3s/hpa.yaml

This file contains the configuration for the Horizontal Pod Autoscaler and will create a new HPA for the php-apache deployment.

apiVersion: autoscaling/v2
kind: HorizontalPodAutoscaler
metadata:
  name: php-apache
  namespace: apache
spec:
  maxReplicas: 4
  metrics:
  - type: Resource
    resource:
      name: cpu
      target:
        averageUtilization: 50
        type: Utilization
  - type: Resource
    resource:
      name: memory
      target:
        averageUtilization: 75
        type: Utilization
  minReplicas: 1
  scaleTargetRef:
    apiVersion: apps/v1
    kind: StatefulSet
    name: php-apache

Once deployed, php-apache will autoscale when either the average CPU usage goes above 50% or the average memory usage for the deployment goes above 75%, with a minimum of 1 pod and a maximum of 4 pods.

kubectl apply -f ~/workshop/k3s/hpa.yaml

2. Validate HPA

kubectl get hpa -n apache

Go to the Workloads or Node Detail tab in Kubernetes and check the HPA deployment.

3. Increase the HPA replica count

Increase the maxReplicas to 8

kubectl edit hpa php-apache -n apache

Save the changes you have made. (Hint: Use Esc followed by :wq! to save your changes).

Congratulations! You have completed the workshop.