Swap support

[kannon92]

What would you like to be added:
I am working on kubernetes/enhancements#2400 which adds swap support. I think that this project could be a good fit for labeling nodes if they have swap enabled.
Why is this needed:
Swap is an important characteristic of a node and it is usually turned off. We are introducing ways for heterogenous nodes for swap so we should have a label for a swap enabled node.

I think the implementation could just check swapon and verify that swap is enabled on the node.

[marquiz]

Thanks @kannon92 for bringing this up. I think this would be a really good enhancement for NFD. We cannot do swapon as we run NFD essentially in an empty/scratch container. We could read /proc/swaps, we'd need to add that (this file only, not the whole procfs) to the volumes/mounts in deployment files. Do you know any other methods for determining if swap is on (like from sysfs which is already mounted inside the NFD container)?

[kannon92]

So I’m happy to contribute!

so as I posted this I realize /proc/swaps is probably the correct path.

I was thinking I could add this to memory in source/memory.

So would I open /proc/swaps and detect if swap is enabled by parsing that file?

And would swap be considered an attribute or a feature?

[marquiz]

So I’m happy to contribute!

@kannon92 🎉

so as I posted this I realize /proc/swaps is probably the correct path.

Yes, I'm not aware of anything better, either

I was thinking I could add this to memory in source/memory.

👍 I think that would be the logical place for it

So would I open /proc/swaps and detect if swap is enabled by parsing that file?

That would be it

And would swap be considered an attribute or a feature?

I think swap would be an "attribute feature" under the memory source, with one "element" or "property" telling if it's on or not. So we'd have a label like feature.node.kubernetes.io/memory-swap.on=<true/false>, and correspondingly memory.swap.on "hidden feature" for custom rules to use as input.

We could target NFD v0.16 which we've been planning to release before the end of March.
/milestone release-0.16

[k8s-ci-robot]

@marquiz: The provided milestone is not valid for this repository. Milestones in this repository: [v0.16, v0.17]

Use /milestone clear to clear the milestone.

In response to this:

So I’m happy to contribute!

@kannon92 🎉

so as I posted this I realize /proc/swaps is probably the correct path.

Yes, I'm not aware of anything better, either

I was thinking I could add this to memory in source/memory.

👍 I think that would be the logical place for it

So would I open /proc/swaps and detect if swap is enabled by parsing that file?

That would be it

And would swap be considered an attribute or a feature?

I think swap would be an "attribute feature" under the memory source, with one "element" or "property" telling if it's on or not. So we'd have a label like feature.node.kubernetes.io/memory-swap.on=<true/false>, and correspondingly memory.swap.on "hidden feature" for custom rules to use as input.

We could target NFD v0.16 which we've been planning to release before the end of March.
/milestone release-0.16

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[marquiz]

/milestone v0.16

[kannon92]

we'd need to add that (this file only, not the whole procfs) to the volumes/mounts in deployment files.

Can you point me where you expect this change to be?

[marquiz]

Can you point me where you expect this change to be?

In this repo we have Helm:
https://github.com/kubernetes-sigs/node-feature-discovery/blob/master/deployment/helm/node-feature-discovery/templates/worker.yaml

and kustomize:
https://github.com/kubernetes-sigs/node-feature-discovery/blob/master/deployment/components/common/worker-mounts.yaml