Use protobuf encoding for core K8s APIs in kueue

[tosi3k]

What type of PR is this?

/kind feature

What this PR does / why we need it:

For core K8s API objects like Pods, Nodes, etc., we can use protobuf encoding which, compared to the default JSON encoding, reduces CPU consumption related to (de)serialization, reduces overall latency of the API calls, reduces memory footprint and the work performed by the GC and results in quicker propagation of objects to event handlers of shared informers.

Core system components of K8s default their serialization method to protobuf for 8 years already: kubernetes/kubernetes#25738.

Which issue(s) this PR fixes:

No issue is opened for that.

Special notes for your reviewer:

Some benchmarks comparing JSON vs. protobuf showcasing how the latter data format (de)serializes faster and uses less memory:

• https://medium.com/@akresling/go-benchmark-json-v-protobuf-4ec3c62ec8d4
• https://www.codingexplorations.com/blog/performance-comparison-protobuf-marshaling-vs-json-marshaling-in-go
• https://medium.com/@david_turner/protocol-buffers-just-how-fast-are-they-9ec19ea580db

Does this PR introduce a user-facing change?

CLI: Use protobuf encoding for core K8s APIs in kueuectl.

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[alculquicondor]

/assign @gabesaba

[alculquicondor]

/ok-to-test

[gabesaba]

/lgtm

thanks for the patch

[k8s-ci-robot]

LGTM label has been added.

Git tree hash: 85ce0f9f9ac09871fb0e038e587831281dde9f53

[alculquicondor]

What about the Kueue controller manager? Can that be changed to use protobuf too?

Also, are there apiservers that don't support protobuf?

[tosi3k]

Also, are there apiservers that don't support protobuf?

Protobuf support for core K8s APIs was added in K8s 1.3 and it's essentially embedded in apiserver - you can't really turn it off anyhow.

What about the Kueue controller manager? Can that be changed to use protobuf too?

If we are touching some custom resources there, then not really - CRs nor dynamic clientsets do not support protobuf encoding.

OTOH, I noticed it uses NewManager function from the controller-runtime repo. A comment above that function's definition implies it would use protobuf for the core API types underneath (link):

// NewManager returns a new Manager for creating Controllers.
// Note that if ContentType in the given config is not set, "application/vnd.kubernetes.protobuf"
// will be used for all built-in resources of Kubernetes, and "application/json" is for other types
// including all CRD resources.

[alculquicondor]

Thank you @tosi3k for the extra context and @mbobrovskyi for the investigation :)

[alculquicondor]

/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: alculquicondor, tosi3k

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[mimowo]

IIUC the change only affects the kueuectl client. Also, is this in fact just for core types?

I would suggest to say in release notes:

CLI: Use protobuf encoding for the client used by kueuectl.

WDYT @tosi3k ?

[tosi3k]

Also, is this in fact just for core types?

Yes - as already stated, custom resources do not support protobuf.

If you try using application/vnd.kubernetes.protobuf content type when talking to K8s API about custom resources, you'd receive an error analogous to the one Mykhailo pasted above.

IIUC the change only affects the kueuectl client.

The PR also touches kjobctl which is not a part of kueuectl, no?

[mimowo]

The PR also touches kjobctl which is not a part of kueuectl, no?

kjobctl is not released yet as part of Kueue, so we don't mention it in release notes yet (for any features)

[mimowo]

Yes - as already stated, custom resources do not support protobuf.

I see, I missed that.

So, I would suggest release note (to emphasize this is just for Kueuectl which is a separate client binary from Kueue):

CLI: Use protobuf encoding for core K8s APIs in Kueuectl.

[tosi3k]

Done