Cluster Autoscaler and Horizontal Pod Autoscaler working together

General Discussions
1

I have a cluster with Cluster Autoscaler activated and HPA for one of my deployments.

This is the HPA definition:

apiVersion: autoscaling/v2beta1
kind: HorizontalPodAutoscaler
metadata:
  name: hpa-resource-metrics-cpu 
spec:
  scaleTargetRef:
    apiVersion: apps/v1 
    kind: ReplicationController 
    name: hello-hpa-cpu 
  minReplicas: 1 
  maxReplicas: 10 
  metrics:
  - type: Resource
    resource:
      name: cpu
      targetAverageUtilization: 50

Now in a situation where my cluster is being used very lightly, that means this deployment will only have 1 available replica.

And since the cluster is not under high usage, it could be the case that the node containing that replica is scheduled for deletion (downscaling).

I don’t want that to happen, since this would make my deployment have a downtime (when the cluster node is deleted, the only replica for the deployment is deleted as well, so it needs to be rescheduled in a new pod).

From this issue: kubectl drain leads to downtime even with a PodDisruptionBudget · Issue #48307 · kubernetes/kubernetes · GitHub, it seems that Pod Disruption Budgets are not applicable to deployments with only 1 replica.

So the only solution to my problem would be to have minReplicas set to 2?

Or is there something else I could do to prevent this downtime, and still let minReplicas as 1?