metrics-server API for kubernetes-client/c

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Ferenc Gerlits

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Jul 20, 2022, 7:01:01 AMJul 20
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Hi,

We use kubernetes-client/c in our project https://github.com/apache/nifi-minifi-cpp and access the metrics-server API `apis/metrics.k8s.io` using the low-level `apiClient_invoke()`, since there is no wrapper for this API in kubernetes-client/c.

I am thinking of contributing a new MetricsServerV1Beta1API wrapper for these API calls (GET pods, GET nodes).  Is that something you would be interested in, and could be accepted as a pull request?

Thank you,
Ferenc

Boshi Lian

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Jul 20, 2022, 2:36:50 PMJul 20
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Jordan Liggitt

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Jul 20, 2022, 2:47:28 PMJul 20
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I think the intent of the kubernetes-client generated clients is to include typed clients for APIs compiled into kube-apiserver, but not for aggregated APIs and CRD-based APIs.

For aggregated and CRD-based APIs, something like https://pkg.go.dev/k8s.io/client-go/dynamic could be useful.

Kevin Wiesmueller

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Jul 20, 2022, 2:55:21 PMJul 20
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I agree with Jordan, I don't think metrics api belongs in the client-go typed client and should rather be provided by metrics-server or whoever defines the metrics-api schema like other non-standard apis. Especially because it's not a default/optional api so having it in the client would formalize it more than it is right now.

Brendan Burns

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Jul 20, 2022, 3:31:32 PMJul 20
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I'm the maintainer of many of these clients (including assisting w/ the C client)

Generating code for CRDs and other extension APIs is actually fairly straightforward to do, there is documentation here for how to do it in Java:


We have taken the approach that we will generate separate API packages based on community contributions.

I hope that you can adapt the Java instructions to generate C code instead, but if you run into problems please file issues on https://github.com/kubernetes-client/c and we can discuss it there.

In addition, we also supply a 'generic' client which can work with any API (at the expense of having typed values in your code) but it may be easier to get started with:


Part of the reason why this is feasible is that all of the clients other than golang are based on code generation rather than hand-written code (though code generation brings it's own set of issues, it's a tradeoff)

--brendan



From: 'Kevin Wiesmueller' via dev <d...@kubernetes.io>
Sent: Wednesday, July 20, 2022 11:55 AM
To: lig...@google.com <lig...@google.com>
Cc: farme...@gmail.com <farme...@gmail.com>; fgerlits <fger...@gmail.com>; dev <d...@kubernetes.io>
Subject: [EXTERNAL] Re: metrics-server API for kubernetes-client/c
 

Hui Yu

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Jul 20, 2022, 10:17:32 PMJul 20
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I agree with Brendan and the other commenters here.

Now the best solution for aggregated APIs and CRD-based APIs using kubernetes-client/c is 'generic' client:
I will document this in the README to make it easier for developers to find this solution.

But I also wonder if we should keep/develop the codebase for the metrics server API `apis/metrics.k8s.io` with a generic client somewhere to avoid duplication of work by other developers? Because more than one developer mentioned before that they implemented the metrics API client using kubernetes-client/c.

Ferenc Gerlits

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Jul 21, 2022, 9:17:55 AMJul 21
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Thanks everyone for your help!  I did not know about genericClient.  I will use that, as it is nice and simple.  And thanks Hui for adding it to the README, I think that will be useful to others, as well.
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