Feature Request: support "empty" group for API resources, i.e. with group == domain

[hypnoglow]

I would like to see kubebuilder support creating APIs with empty groups. By that I mean that the actual apiVersion of CRD to be domain/version without additional group prefix.

I think this can be very helpful for controllers/operators with a very narrow scope and a small number of Kind-s fitting into single "root" group.

Consider popular examples, such as cert-manager or jaeger-operator:

apiVersion: cert-manager.io/v1alpha2
kind: Certificate
metadata:
  name: example-com

apiVersion: jaegertracing.io/v1
kind: Jaeger
metadata:
  name: simplest

In this examples there is no "groups" in terms of kubebuilder, and one group in terms of Kubernetes resource (for kubebuilder it isgroup == domain). And for many such cases it would be desirable to design APIs in a similar simple way.

/kind feature

[Adirio]

@DirectXMan12 @mengqiy @droot @camilamacedo86 what do you think about this? Should we implement this feature.

[camilamacedo86]

Hi @hypnoglow,

Let's see if I understood your RFE.
Currently, we do:

kubebuilder init --domain my.domain
kubebuilder create api --group webapp --version v1 --kind Guestbook

Then, what you are asking here is the tool allows:

kubebuilder init --domain my.domain
kubebuilder create api --version v1 --kind Guestbook

Which means that if len(group) < 0 then group= project domain
Then, in this example, it would be the same result of:

kubebuilder create api --group my.domain --version v1 --kind Guestbook

However, the above command would gen:

apiVersion: my.domain.my.domain/v1
kind: Guestbook

Which shows not the expected result and you are looking for :

apiVersion: my.domain/v1
kind: Guestbook

Then, IMO it means allow Kubebuilder gen API without a group.
Please, let me know if I misunderstand something here.

Shows that k8s API allows we enable and disable Groups. See https://kubernetes.io/docs/concepts/overview/kubernetes-api/#enabling-api-groups
So, wdyt @mengqiy and @DirectXMan12? It also would block the project for the MultiGroup option as well. Then, IMO in this scenario, we would need to save in the Project file that GVK is group=empty and never allowed MultiGroup for the project.

PS.: tks @Adirio tks for your help to understand what @hypnoglow is looking for here too.

[Adirio]

Regarding multi-group, we just would need to use a well-known directory name, such as "core" (following k8s). Would be nice if we could make my.domain/v1 and core.my.domain be synonyms, but I'm not sure if this is feasible.

Regarding the GVK stored in the config file, I would just not store it as that will be clar enough and reading and writting will be easy to implement, just requiring a json:"group,omitmepty" field annotation.

[DirectXMan12]

/approve on what @Adirio said

[Adirio]

I don't know about the feasability of the core.my.domain and my.domain being the same though. Any clue on that?

[DirectXMan12]

␀.my.domain clearly is the superior answer, with ∅.my.domain being a close second

[fejta-bot]

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[jpkrohling]

Wanted to show my support for this issue. As one of the developers behind the Jaeger and OpenTelemetry Operators, we are stuck with the Operator SDK 0.18.x until a guidance is provided for this issue here.

EDIT: the group seems to be required only for the initial generation. Generating it as, say, core.opentelemetry.io and replacing it by opentelemetry.io seems to actually work.

[joelanford]

There is a messy workaround for this though, right?

Something like:

kubebuilder init --domain=io
kubebuilder create api --group=jaegertracing --version=v1 --kind=Metric`

Does that break something? Maybe it precludes a "core" group AND APIs under subdomain groups?

[jpkrohling]

I ended up doing something similar: I generated it with --domain=jaegertracing.io and the API as --group=core. I then proceeded to replace all core.jaegertracing.io entries with jaegertracing.io. This seems to be working, but not sure it will cause me problems later on.

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[camilamacedo86]

/remove-lifecycle rotten

[DirectXMan12]

FYI, I think this is largely just waiting for someone to implement.

/good-first-issue

[k8s-ci-robot]

@DirectXMan12:
This request has been marked as suitable for new contributors.

Please ensure the request meets the requirements listed here.

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In response to this:

FYI, I think this is largely just waiting for someone to implement.

/good-first-issue

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[prafull01]

/assign