windows: mutate additional kubeletconfiguration fields on join

[neolit123]

PRs for the points listed below:

• kubeadm: special case some KubeletConfiguration defaults on Windows kubernetes#123136
• kubelet: warn instead of error for unsupported options on Windows kubernetes#123137

---

during join of a Windows worker node we download the kubelet-config from the cluster as usual, then we apply some mutations, notably around problematic paths with drive on Windows:
https://github.com/kubernetes/kubernetes/blob/master/cmd/kubeadm/app/componentconfigs/kubelet_windows.go

but we are missing some more fields that do not work on Windows.

the kubelet defaults for EnforceNodeAllocatable=pods or CgroupsPerQOS=true are simply rejected on Windows with errors:

E1123 02:11:01.358586    5616 server.go:224] "Failed to validate kubelet configuration" err="[invalid configuration: CgroupsPerQOS (--cgroups-per-qos) true is not supported on Windows, invalid configuration: EnforceNodeAllocatable (--enforce-node-allocatable) [pods] is not supported on Windows]" path="&TypeMeta{Kind:,APIVersion:,}"

why are these the defaults, who knows...but that's not OS portable.

what can be done is override the defaults similarly to this:
https://github.com/kubernetes-sigs/sig-windows-tools/blob/28a4c4f4e9e0b65d4d1ed1841e11eca5a62bfafe/hostprocess/PrepareNode.ps1#L73

but using the kubeletconfiguration struct.
https://kubernetes.io/docs/reference/config-api/kubelet-config.v1beta1/

enforceNodeAllocatable: ""
cgroupsPerQOS: false

alternatively

we can try convincing the kubelet maintainers to change these defaults on Windows. that is the better solution, but similar requests have failed in the past.

https://github.com/kubernetes/kubernetes/blob/d61cbac69aae97db1839bd2e0e86d68f26b353a7/pkg/kubelet/apis/config/validation/validation_windows.go#L29
https://github.com/kubernetes/kubernetes/blob/d61cbac69aae97db1839bd2e0e86d68f26b353a7/cmd/kubelet/app/options/osflags_windows.go
https://github.com/kubernetes/kubernetes/blob/d61cbac69aae97db1839bd2e0e86d68f26b353a7/pkg/kubelet/apis/config/v1beta1/defaults.go#L148
https://github.com/kubernetes/kubernetes/blob/d61cbac69aae97db1839bd2e0e86d68f26b353a7/pkg/kubelet/apis/config/v1beta1/defaults.go#L245-L246

note, we do not own any tests other than unit tests for this, so best we can do is to just add the change and see if we can remove the flag overrides from https://github.com/kubernetes-sigs/sig-windows-tools/blob/28a4c4f4e9e0b65d4d1ed1841e11eca5a62bfafe/hostprocess/PrepareNode.ps1#L73, which is owned by sig-windows.

[ndixita]

@neolit123 could you please add more details like K8s version on which we can reproduce this issue?

[neolit123]

@neolit123 could you please add more details like K8s version on which we can reproduce this issue?

@ndixita this is latest master of k/k.
ideally SIG node must take action on the above or kubeadm (SIG CL ) or Windows scripts (SIG Windows) must workaround the problem.

[pacoxu]

Why not just skip or ignore the args on Windows kubelet?

Edited: Just read kubernetes/kubernetes#123137. I prefer this change.

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[neolit123]

kubernetes/kubernetes#123137
merged, there isn't any AI here.

if more fields in kubeletconfig in the future break windows kubelet that's should be fixed in kubelet code like
kubernetes/kubernetes#123137 did.

in terms of what we do here:
https://github.com/kubernetes/kubernetes/blob/master/cmd/kubeadm/app/componentconfigs/kubelet_windows.go

i don't think that can be fixed because client-go/kubelet uses the Abs() golang stdlib function which is not Windows compatible.