How do I update a Kubernetes autoscaler? - kubernetes

Question

I have created a Kubernetes autoscaler, but I need to change its parameters. How do I update it?
I've tried the following, but it fails:
✗ kubectl autoscale -f docker/production/web-controller.yaml --min=2 --max=6
Error from server: horizontalpodautoscalers.extensions "web" already exists

Answer 1

You can always interactively edit the resources in your cluster. For your autoscale controller called web, you can edit it via:
kubectl edit hpa web
If you're looking for a more programmatic way to update your horizontal pod autoscaler, you would have better luck describing your autoscaler entity in a yaml file, as well. For example, here's a simple Replication Controller, paired with a Horizontal Pod Autoscale entity:
apiVersion: v1
kind: ReplicationController
metadata:
name: nginx
spec:
replicas: 2
template:
metadata:
labels:
run: nginx
spec:
containers:
- name: nginx
image: nginx
ports:
- containerPort: 80
---
apiVersion: autoscaling/v1
kind: HorizontalPodAutoscaler
metadata:
name: nginx
namespace: default
spec:
maxReplicas: 3
minReplicas: 2
scaleTargetRef:
apiVersion: v1
kind: ReplicationController
name: nginx
With those contents in a file called nginx.yaml, updating the autoscaler could be done via kubectl apply -f nginx.yaml.

Answer 2

You can use the kubectl patch command as well, to see its current status
kubectl get hpa <autoscaler-name-here> -o json
An example output:
{
"apiVersion": "autoscaling/v1",
"kind": "HorizontalPodAutoscaler",
"metadata": {
...
"name": "your-auto-scaler",
"namespace": "your-namespace",
...
},
"spec": {
"maxReplicas": 50,
"minReplicas": 2,
"scaleTargetRef": {
"apiVersion": "extensions/v1beta1",
"kind": "Deployment",
"name": "your-deployment"
},
"targetCPUUtilizationPercentage": 40
},
"status": {
"currentReplicas": 1,
"desiredReplicas": 2,
"lastScaleTime": "2017-12-13T16:23:41Z"
}
}
If you want to update the minimum number of replicas:
kubectl -n your-namespace patch hpa your-auto-scaler --patch '{"spec":{"minReplicas":1}}'
The same logic applies to other parameters found in the autoscaler configuration, change minReplicas to maxReplicas if you want to update the maximum number of allowed replicas.

Answer 3

First delete the autoscaler and then re-create it:
✗ kubectl delete hpa web
✗ kubectl autoscale -f docker/production/web-controller.yaml --min=2 --max=6

Answer 4

I tried multiple options but the one which works the best is
First delete the existing hpa
kubectl delete hpa web
then recreate another one
kubectl autoscale -f docker/production/web-controller.yaml --min=2 --max=6