Show k8s API Deprecation Warnings

[danielhelfand]

Describe the problem/challenge you have

With the addition of #245, kapp by default will not show API deprecation notices as shown in this commit: 4f554b0

Users may want to see these deprecation notices as part of using kapp, so it might be helpful to provide an option to show deprecation notices in output. This will help users catch deprecation notices in advance sooner as described here.

Describe the solution you'd like

My initial thought is to provide a command line option (e.g. --show-deprecation-warnings) with kapp deploy/delete commands that will show warnings like below:

W0719 09:22:53.305568   47369 warnings.go:67] storage.k8s.io/v1beta1 VolumeAttachment is deprecated in v1.19+, unavailable in v1.22+; use storage.k8s.io/v1 VolumeAttachment
W0719 09:22:53.305624   47369 warnings.go:67] storage.k8s.io/v1beta1 CSIDriver is deprecated in v1.19+, unavailable in v1.22+; use storage.k8s.io/v1 CSIDriver
W0719 09:22:53.305568   47369 warnings.go:67] networking.k8s.io/v1beta1 IngressClass is deprecated in v1.19+, unavailable in v1.22+; use networking.k8s.io/v1 IngressClassList
W0719 09:22:53.305569   47369 warnings.go:67] scheduling.k8s.io/v1beta1 PriorityClass is deprecated in v1.14+, unavailable in v1.22+; use scheduling.k8s.io/v1 PriorityClass
W0719 09:22:53.306062   47369 warnings.go:67] extensions/v1beta1 Ingress is deprecated in v1.14+, unavailable in v1.22+; use networking.k8s.io/v1 Ingress
W0719 09:22:53.306093   47369 warnings.go:67] coordination.k8s.io/v1beta1 Lease is deprecated in v1.19+, unavailable in v1.22+; use coordination.k8s.io/v1 Lease
W0719 09:22:53.309686   47369 warnings.go:67] storage.k8s.io/v1beta1 StorageClass is deprecated in v1.19+, unavailable in v1.22+; use storage.k8s.io/v1 StorageClass
W0719 09:22:53.312761   47369 warnings.go:67] networking.k8s.io/v1beta1 Ingress is deprecated in v1.19+, unavailable in v1.22+; use networking.k8s.io/v1 Ingress
W0719 09:22:53.317088   47369 warnings.go:67] rbac.authorization.k8s.io/v1beta1 Role is deprecated in v1.17+, unavailable in v1.22+; use rbac.authorization.k8s.io/v1 Role
W0719 09:22:53.318580   47369 warnings.go:67] storage.k8s.io/v1beta1 CSINode is deprecated in v1.17+, unavailable in v1.22+; use storage.k8s.io/v1 CSINode
W0719 09:22:53.318716   47369 warnings.go:67] apiregistration.k8s.io/v1beta1 APIService is deprecated in v1.19+, unavailable in v1.22+; use apiregistration.k8s.io/v1 APIService
W0719 09:22:53.319085   47369 warnings.go:67] rbac.authorization.k8s.io/v1beta1 RoleBinding is deprecated in v1.17+, unavailable in v1.22+; use rbac.authorization.k8s.io/v1 RoleBinding
W0719 09:22:53.333891   47369 warnings.go:67] admissionregistration.k8s.io/v1beta1 MutatingWebhookConfiguration is deprecated in v1.16+, unavailable in v1.22+; use admissionregistration.k8s.io/v1 MutatingWebhookConfiguration
W0719 09:22:53.334257   47369 warnings.go:67] apiextensions.k8s.io/v1beta1 CustomResourceDefinition is deprecated in v1.16+, unavailable in v1.22+; use apiextensions.k8s.io/v1 CustomResourceDefinition
W0719 09:22:53.401374   47369 warnings.go:67] admissionregistration.k8s.io/v1beta1 ValidatingWebhookConfiguration is deprecated in v1.16+, unavailable in v1.22+; use admissionregistration.k8s.io/v1 ValidatingWebhookConfiguration
W0719 09:22:53.403840   47369 warnings.go:67] rbac.authorization.k8s.io/v1beta1 ClusterRole is deprecated in v1.17+, unavailable in v1.22+; use rbac.authorization.k8s.io/v1 ClusterRole
W0719 09:22:53.404188   47369 warnings.go:67] certificates.k8s.io/v1beta1 CertificateSigningRequest is deprecated in v1.19+, unavailable in v1.22+; use certificates.k8s.io/v1 CertificateSigningRequest
W0719 09:22:53.406843   47369 warnings.go:67] rbac.authorization.k8s.io/v1beta1 ClusterRoleBinding is deprecated in v1.17+, unavailable in v1.22+; use rbac.authorization.k8s.io/v1 ClusterRoleBinding

So the final command might look like:

kapp deploy -a app -f app.yml --show-deprecation-warnings

It might also be nice to format the deprecation notices in a way that fits kapp's current UX.

Anything else you would like to add:

Information on client handling: https://kubernetes.io/blog/2020/09/03/warnings/#customize-client-handling

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[cppforlife]

i would change the flag to --deprecation-warnings=bool with a possibly default of true since i think kubectl shows warnings by default as well. should we default to false? (if we do, who would turn them on?)

also we should only show same warning once to the user.

[renuy]

We will add the flag and show warnings (true) by default.

[danielhelfand]

We will add the flag and show warnings (true) by default.

Would it make sense to change the flag then? To something like --silence-deprecation-notices with a default of false? I think the UX is a bit better to me this way.

[praveenrewar]

Would it make sense to change the flag then? To something like --silence-deprecation-notices with a default of false? I think the UX is a bit better to me this way.

I agree, this is also in line with Go's default value for bool.

also we should only show same warning once to the user.

Or, we can show a message to users along with the warnings, that they can silence them by using this flag.