Scale-down broken for Cloud Providers not implementing NodeGroup.GetOptions()

[apricote]

Which component are you using?:

cluster-autoscaler

What version of the component are you using?:

Component version: master/e1b03fac9958791790bfc18eeba9fab5cac0ccc1

What k8s version are you using (kubectl version)?:

kubectl version Output

$ kubectl version
Client Version: version.Info{Major:"1", Minor:"27", GitVersion:"v1.27.4", GitCommit:"fa3d7990104d7c1f16943a67f11b154b71f6a132", GitTreeState:"archive", BuildDate:"1980-01-01T00:00:00Z", GoVersion:"go1.20.6", Compiler:"gc", Platform:"linux/amd64"}
Kustomize Version: v5.0.1
Server Version: version.Info{Major:"1", Minor:"27", GitVersion:"v1.27.4+k3s1", GitCommit:"36645e7311e9bdbbf2adb79ecd8bd68556bc86f6", GitTreeState:"clean", BuildDate:"2023-07-28T09:46:04Z", GoVersion:"go1.20.6", Compiler:"gc", Platform:"linux/amd64"}

What environment is this in?:

Hetzner Cloud using k3s/k3sup, local development environment

What did you expect to happen?:

A successful scale down of unused nodes for my cloud provider hetzner.

What happened instead?:

Scale down never happened and instead this error message was printed every reconciliation loop:

E0815 10:24:08.433379       1 post_filtering_processor.go:59] Failed to get autoscaling options for node group pool1: Not implemented

How to reproduce it (as minimally and precisely as possible):

• Use a cloudprovider that has NodeGroup.GetOptions() returning nil, cloudprovider.ErrNotImplemented

I can provide a full script, but do intend to submit a patch for this anyway.

Anything else we need to know?:

Some callsites of NodeGroup.GetOptions() do not properly handle the cloudprovider.ErrNotImplemented error. This is a valid response and should not cause a broken scale-down operation for these cloud providers.

See #5695 (comment)

[apricote]

/assign