Implement ComponentConfig by default & stop using (most) flags

[luxas]

/kind feature
related KEPs here: https://github.com/kubernetes/enhancements/tree/master/keps/sig-cluster-lifecycle/wgs

cc @DirectXMan12 as per contributor summit discussion

[DirectXMan12]

Probably needs equivalent CR support? Need to take a closer look. In the mean time, people should feel free to weigh in with more info

/help-wanted

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/lifecycle stale

[DirectXMan12]

/ifecycle frozen

[stealthybox]

/wg component-standard

[stealthybox]

Related kubernetes-sigs/controller-runtime#518

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/lifecycle rotten

[DirectXMan12]

/lifecycle frozen

[christopherhein]

/assign

[christopherhein]

We've gotten the initial implementation done in kubernetes-sigs/controller-runtime#891 using kubernetes-sigs/controller-runtime#895 to track the progress. Do you think we're ready to do an initial implementation Kubebuilder @DirectXMan12 ? The changes as I see could be something like…

When you kubebuilder init you could pass --component-config which would add a couple of small changes to the main.go like adding .AndFromOrDie(cfg.FromFile()) to the ctrl.Options{} passed into ctrl.NewManager() as well as configuring the config/manager/kustomization.yaml to load a ConfigMap from a file and scaffold that file in config/manager/config.yaml this way out of the box you have a built-in configfile to configure how the controller manager is run if you want to use this and you could exclude --component-config if you didn't.

An extended version of this could be --component-config={CustomKind} which could scaffold custom type similar to https://github.com/kubernetes-sigs/controller-runtime/blob/master/examples/configfile/custom/main.go#L49-L53 + https://github.com/kubernetes-sigs/controller-runtime/blob/master/examples/configfile/custom/v1alpha1/types.go, this would require automatically setting multigroup: true since configs are typically config.{domain} with a kind of {Name}Configuration.

What do you all think? (My hesitation would be that it's defined as an alpha API and we don't have a versioning strategy in-place yet)

[christopherhein]

Looks like #1746 should be done first which is involved in updating to the latest CR build.