nfd-topology-updater: retrieve kubelet config from API `/configz`

[Garrybest]

Now nfd-topology-updater tries to retrieve topologyManagerPolicy of a node by reading kubelet config file. However, sometimes we use command line to start Kubelet instead of the config file, or sometimes the config file is modified but Kubelet has not restarted to make this file take effect.

I think we'd better retrieve the latest config from Kubelet API /configz, Kubelet will return the configuration in its memory. This config is obviously accurate.

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[Garrybest]

/cc @swatisehgal @fromanirh

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[Garrybest]

I have tested the whole deployment in my own minikube, the logs show this API would works.

I0702 12:03:12.757291       1 main.go:74] detected kubelet Topology Manager policy "SingleNUMANodeContainerLevel"

[ffromani]

/cc @Tal-or

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[ffromani]

@Tal-or

[Tal-or]

Very nice. I don't recall atm why eventually we decided not to move on in this direction, I need to do some digging to find out why. It would be great if we can have some integration/e2e as part of this PR for validating this feature.

[Tal-or]

There is some note in K8S docs: https://v1-23.docs.kubernetes.io/docs/tasks/administer-cluster/reconfigure-kubelet/#generating-a-file-that-contains-the-current-configuration

which says: Caution: The kubelet's configz endpoint is there to help with debugging, and is not a stable part of kubelet behavior. Do not rely on the behavior of this endpoint for production scenarios or for use with automated tools.

This is the reason why we decided to not pursue this direction eventually. Maybe this warning isn't relevant anymore but this is something that should be figured out.

[Garrybest]

There is some note in K8S docs: https://v1-23.docs.kubernetes.io/docs/tasks/administer-cluster/reconfigure-kubelet/#generating-a-file-that-contains-the-current-configuration

which says: Caution: The kubelet's configz endpoint is there to help with debugging, and is not a stable part of kubelet behavior. Do not rely on the behavior of this endpoint for production scenarios or for use with automated tools.

This is the reason why we decided to not pursue this direction eventually. Maybe this warning isn't relevant anymore but this is something that should be figured out.

Thanks for reminding. Now I try to use token first. If failed, we could fall back to use config file.

[marquiz]

/ok-to-test

[marquiz]

Thanks @Garrybest for the PR. I think this makes sense.

I'm sorry I didn't have the time to review the PR this week and now I'm off to summer holidays 🙄 I will be off for four weeks but will reivew this when I'm back.

I'm not entirely sure about the fallback 🧐 How about changing -kubelet-config-file to -kubelet-config and you could the give a http:// endpoint or a file://pointing to a local file?

[ffromani]

I'm not entirely sure about the fallback monocle_face How about changing -kubelet-config-file to -kubelet-config and you could the give a http:// endpoint or a file://pointing to a local file?

I like this idea!

[Garrybest]

/retest

[Garrybest]

Thanks @marquiz, I like this suggestion. Very cool 😄

[ArangoGutierrez]

PING - How are we going with this PR, will be nice to have it as part of 0.12

[Garrybest]

cc @marquiz, could you please take a look here?

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[k8s-ci-robot]

@Garrybest: PR needs rebase.

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[marquiz]

ping @Garrybest are you still working on this?

[Garrybest]

Sorry, I'm too busy recently. I will keep working on this ASAP.

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[Garrybest]

Thanks for the suggestions!

[Garrybest]

/retest

[Garrybest]

It seems that there is something wrong with the robot 🤣

[Garrybest]

I think we can merge this but I'll give some time to others chime in, too

No problem. Thanks again for your rigorous reviewing 😄

[marquiz]

/retest

[ffromani]

Thanks for working on this and the quick responses @Garrybest blush I think we can merge this but I'll give some time to others chime in, too

There really seems to be something odd in prow... /retest

Thanks for this! I don't have any additional comments.

[marquiz]

Thanks for this! I don't have any additional comments.

👍 /assign @fmuyassarov

prow had some issues so please fix those

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Garrybest, marquiz

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[marquiz]

@fmuyassarov @zvonkok you wanna check this or should we just merge?