Not able to change compute offering in a Kubernetes cluster when using KVM VMs

[saffronjam]

ISSUE TYPE

• Improvement Request

COMPONENT NAME

Kubernetes

CLOUDSTACK VERSION

4.18

CONFIGURATION

Default, following guides provided by CloudStack

OS / ENVIRONMENT

Ubuntu 22.04

KVM hypervisor

SUMMARY

Changing compute offering when scaling Kubernetes cluster results in error saying that it is not support.

".. on KVM is not supported!"

I expect to be able to change the compute offering after the cluster is created.
For a use case such as: increasing the RAM since a heavy app requires it.

STEPS TO REPRODUCE

- create a Kubernetes cluster on KVM VMs
- scale the cluster with a different compute offering

EXPECTED RESULTS

I expect to be able to change compute offering for a Kubernetes cluster

ACTUAL RESULTS

Error popup saying that it is not supported on KVM.

Error in code:
https://github.dev/apache/cloudstack/blob/2ac1b7e9599b048d3490577b0823752fc7a740d7/plugins/integrations/kubernetes-service/src/main/java/com/cloud/kubernetes/cluster/actionworkers/KubernetesClusterScaleWorker.java#L240

[saffronjam]

Adding on to this, I presume this has to do with the "running" part.

Error message:
... cluster with running VMs on hypervisor ...

However, if I would stop the Kubernetes cluster, then I don't have any option to scale it. So:

1. Cluster is in Running state -> Can't scale with new compute offering because the virtual machines are running
2. Cluster is NOT in Running state -> Can't scale with new compute offering because there is no button to do it (only "Start cluster" and "Delete cluster")

[kiranchavala]

Hi @saffronjam

I was able to reproduce the issue

Currently scaling of running vms is only supported on vmware and xenserver

http://docs.cloudstack.apache.org/en/latest/adminguide/virtual_machines.html?highlight=scaling#cpu-and-memory-scaling-for-running-vms

It could be a limitation on the kvm side

http://docs.cloudstack.apache.org/en/latest/adminguide/virtual_machines.html?highlight=scaling#cpu-and-memory-scaling-for-running-vms

Can you follow these steps

1. Stop the Kubernetes cluster , the vm's associated with kubernetes cluster will also be in stopped state

2. Now go to instance > stopped vm of the k8s cluster > scale the vm

or Execute the api call

https://cloudstack.apache.org/api/apidocs-4.18/apis/scaleVirtualMachine.html

3. Start the Kubernetes cluster

[saffronjam]

I tried the approach suggested above, and the nodes appears to have been scaled.
However, I noticed that the cluster configuration is no longer synchronized with the nodes. The cluster still says it is using the old configuration.

Since I thought that this would cause broken scaling (new nodes would get the old offering), I reverted the changes.

[yadvr]

Fixed in #7475