Support kubeletConfiguration.featureGates in Provisioner spec

[OrBin]

Description

What problem are you trying to solve? Set feature gates for a kubelet.

How important is this feature to you? It's necessary for us to be able to use swap memory on Karpenter-controlled nodes when using kubelet version 1.27 or lower.

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[njtran]

Karpenter recently added v1beta1 APIs, where we're in the process of deprecating v1alpha5 APIs. Which feature gates are you looking to enable? Are you using EKS?

[OrBin]

I want to enable NodeSwap and I am using EKS.

Now I see this, which I didn't see before; Is Drift the only supported feature gate?

[alec-w]

I think this is a separate item to the feature gates for the Karpenter APIs. This is about being able to pass featureGates through to the kubelet to enable feature gates for a set of nodes.

In our case we wanted to enable the feature gate MinDomainsInPodTopologySpread and so had node pool config

spec:
  template:
    spec:
      kubelet:
        featureGates:
          MinDomainsInPodTopologySpread: true

but got error when applying this
strict decoding error: unknown field "spec.template.spec.kubelet.featureGates"

Our attempt was based on https://karpenter.sh/preview/concepts/nodepools/#spectemplatespeckubelet, kubelet configuration API reference https://kubernetes.io/docs/reference/config-api/kubelet-config.v1beta1/#kubelet-config-k8s-io-v1beta1-KubeletConfiguration and available feature gates https://kubernetes.io/docs/reference/command-line-tools-reference/feature-gates/

Server version: v1.25.15-eks-4f4795d
Client version: v1.25.15
kubeletVersion: v1.25.15-eks-e71965b

Although I see that the kubelet configuration (and therefore featureGates) doesn't exist under the v1 reference https://kubernetes.io/docs/reference/config-api/kubelet-config.v1/ - so could it be that this is supported by Karpenter but not the kubelet version we're using?

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[jonathan-innis]

I'm closing this one as Not Planned since I don't think there is any plan among CloudProviders to surface this set of arguments generally. If you are interested in adding more feedback for AWS, here's the larger GH issue: aws/karpenter-provider-aws#5833