Simpli Learn: Autoscaling: Horizontal Pod Autoscaler

Create a deployment using the image php-apache and expose it

Lets create the deployment using a yaml file -> php-apache.yaml

apiVersion: apps/v1
kind: Deployment
metadata:
name: php-apache
spec:
selector:
    matchLabels:
      run: php-apache
replicas: 1
template:
    metadata:
      labels:
        run: php-apache
    spec:
      containers:
      - name: php-apache
        image: k8s.gcr.io/hpa-example
        ports:
        - containerPort: 80
        resources:
          limits:
            cpu: 500m
          requests:
            cpu: 200m
---
apiVersion: v1
kind: Service
metadata:
name: php-apache
labels:
    run: php-apache
spec:
ports:
- port: 80
selector:
    run: php-apache

Create the deployment using kubectl apply command

$ kubectl apply -f php-apache.yaml
deployment.apps/php-apache created
service/php-apache created

$ kubectl get pods
NAME READY STATUS RESTARTS AGE
php-apache-7656945b6b-pzp9h 0/1 ContainerCreating 0 22s

$ kubectl get pods
NAME READY STATUS RESTARTS AGE
php-apache-7656945b6b-pzp9h 1/1 Running 0 51s

Create the horizontal pod autoscaler

$ kubectl autoscale deployment php-apache --cpu-percent=50 --min=1 --max=10
horizontalpodautoscaler.autoscaling/php-apache autoscaled

You can check the current status of the newly-made HorizontalPodAutoscaler, by running:

$ kubectl get hpa
NAME REFERENCE TARGETS MINPODS MAXPODS REPLICAS AGE
php-apache Deployment/php-apache <unknown>/50% 1 10 1 31s

Increase the load: Run the below command in a separate terminal

$ kubectl run -i --tty load-generator --rm --image=busybox:1.28 --restart=Never -- /bin/sh -c "while sleep 0.01; do wget -q -O- http://php-apache; done"

Now on the main terminal run the following command

$ kubectl get hpa php-apache --watch

You should see the higher CPU load and replicas

NAME REFERENCE TARGET MINPODS MAXPODS REPLICAS AGE
php-apache Deployment/php-apache/scale 305% / 50% 1 10 1 3m

NAME REFERENCE TARGET MINPODS MAXPODS REPLICAS AGE
php-apache Deployment/php-apache/scale 305% / 50% 1 10 7 3m

$ kubectl get deployment php-apache
NAME READY UP-TO-DATE AVAILABLE AGE
php-apache 7/7 7 7 19m

Stop generating the load in the terminal where you created the Pod that runs a busybox image, terminate the load generation by typing <Ctrl> + C

$ kubectl get hpa php-apache --watch
NAME         REFERENCE                     TARGET       MINPODS   MAXPODS   REPLICAS   AGE
php-apache   Deployment/php-apache/scale   0% / 50%     1         10        1          11m

Deployment also shows that it has scaled down

$ kubectl get deployment php-apache
NAME         READY   UP-TO-DATE   AVAILABLE   AGE
php-apache   1/1     1            1           27m

Once CPU utilization dropped to 0, the HPA automatically scaled the number of replicas back down to 1

Tuesday, August 29, 2023

Autoscaling: Horizontal Pod Autoscaler