export swap behavior via label

[fmuyassarov]

This patch exports a label indicating the kubelet's configured swap behavior. By default, it reads from /var/lib/kubelet/config.yaml. If a custom kubelet config path is used, it can be set via the -kubelet-config-path flag. If the swap behavior is not specified, NoSwap is assumed (matching kubelet's default).

Note: feature.node.kubernetes.io/memory-swap.behavior (or in general kubelet's memorySwap.swapBehavior) reflects whether k8s workloads are allowed to use swap. A node may have swap enabled, but if kubelet is set to NoSwap, pods cannot use it. As such, the behavior label will be exported only if node level swap is enabled.

      feature.node.kubernetes.io/memory-swap: "true"
      feature.node.kubernetes.io/memory-swap.behavior: LimitedSwap

Fixes: https://github.com/kubernetes-sigs/node-feature-discovery/issues/2178

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[APPROVALNOTIFIER] This PR is NOT APPROVED

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[fmuyassarov]

/test pull-node-feature-discovery-build-image-cross-generic

[fmuyassarov]

@fmuyassarov thank you for the patch and working on this. Let's get this finalized.

My main comment is that in topology-updater we already read the kubelet config (read from the kubelet configz endpoint by default), helpers are in pkg/utils/kubeconf/. Could we do the same on nfd-worker?

I will check that.

[fmuyassarov]

Hi @marquiz . I've reworked the patch to utilize the configz. The current state is missing the documentation update which I thought of adding once I get a green light that this the right approach. Please take a look.

[ArangoGutierrez]

/retest

[marquiz]

@fmuyassarov independent of where we logically put the new feature, I think the detection should be outside nfd-worker core package. If we keep it in memory.swap, then probably the feature name should somehow reflect that it's kubelet behavior.

[fmuyassarov]

@fmuyassarov independent of where we logically put the new feature, I think the detection should be outside nfd-worker core package. If we keep it in memory.swap, then probably the feature name should somehow reflect that it's kubelet behavior.

The reason for splitting the detection between memory and worker pkgs is that, memory pkg doesn't have access to the kubeconfig & kubelet. Technically speaking, there is no need to do anything within the memory pkg. But, the reason I used memory pkg is because we are detecting the memory related feature. Sure, it is via kubelet, but the main thing is not kubelet, but the memory. Since we already had a logic of detecting the swap memory within the memory pkg, I thought of extending it for swap memory type too.

[k8s-ci-robot]

@fmuyassarov: The following tests failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
pull-node-feature-discovery-verify-master	f5adaa8675b34309e718e3835bc54b58c6e6d6d8	link	true	/test pull-node-feature-discovery-verify-master
pull-node-feature-discovery-e2e-test-master	f5adaa8675b34309e718e3835bc54b58c6e6d6d8	link	true	/test pull-node-feature-discovery-e2e-test-master

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