[Issue] no kind "CronTab" is registered for version "stable.example.com/v1"

[yang-wang11]

I made a copy from cnat to crontab, below is its definition of CRD

apiVersion: apiextensions.k8s.io/v1
kind: CustomResourceDefinition
metadata:
  # name must match the spec fields below, and be in the form: <plural>.<group>
  name: crontabs.stable.example.com
spec:
  # group name to use for REST API: /apis/<group>/<version>
  group: stable.example.com
  # list of versions supported by this CustomResourceDefinition
  versions:
    - name: v1
      # Each version can be enabled/disabled by Served flag.
      served: true
      # One and only one version must be marked as the storage version.
      storage: true
      additionalPrinterColumns:
      - name: schedule 
        type: string 
        jsonPath: .spec.cronSpec      
      schema:
        openAPIV3Schema:
          type: object
          properties:
            spec:
              type: object
              properties:
                cronSpec:
                  type: string
                image:
                  type: string
                replicas:
                  type: integer
  # either Namespaced or Cluster
  scope: Namespaced
  names:
    # plural name to be used in the URL: /apis/<group>/<version>/<plural>
    plural: crontabs
    # singular name to be used as an alias on the CLI and for display
    singular: crontab
    # kind is normally the CamelCased singular type. Your resource manifests use this.
    kind: CronTab
    # shortNames allow shorter string to match your resource on the CLI
    shortNames:
    - ct

  

the code of types.go

package v1

import (
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
)

type CrontabSpecV1 struct {
	CronSpec string `json:"cronSpec"`
	Image    string `json:"image"`
}

// +genclient
// +k8s:deepcopy-gen:interfaces=k8s.io/apimachinery/pkg/runtime.Object

type Crontab struct {
	metav1.TypeMeta   `json:",inline"`
	metav1.ObjectMeta `json:"metadata,omitempty"`

	Spec CrontabSpecV1 `json:"spec,omitempty"`
}

// +k8s:deepcopy-gen:interfaces=k8s.io/apimachinery/pkg/runtime.Object

type CrontabList struct {
	metav1.TypeMeta `json:",inline"`
	metav1.ListMeta `json:"metadata,omitempty"`

	Items []Crontab `json:"items"`
}

and the code of register.go

// Define your schema name and the version
var SchemeGroupVersion = schema.GroupVersion{
	Group:   "stable.example.com",
	Version: "v1",
}

var (
	SchemeBuilder = runtime.NewSchemeBuilder(addKnownTypes)
	AddToScheme   = SchemeBuilder.AddToScheme
)

// Resource takes an unqualified resource and returns a Group qualified GroupResource
func Resource(resource string) schema.GroupResource {
	return SchemeGroupVersion.WithResource(resource).GroupResource()
}

func Kind(kind string) schema.GroupKind {
	return SchemeGroupVersion.WithKind(kind).GroupKind()
}

// Adds the list of known types to the given scheme.
func addKnownTypes(scheme *runtime.Scheme) error {
	scheme.AddKnownTypes(SchemeGroupVersion,
		&CrontabList{},
		&Crontab{},
	)
	metav1.AddToGroupVersion(scheme, SchemeGroupVersion)
	return nil
}

after the commandgenerate-groups.sh "deepcopy,client,informer,lister" be executed, following code raise an error

	client, e := versioned.NewForConfig(config)
	if e != nil {
		panic(e.Error())
	}
	crontab, err := client.StableV1().Crontabs("default").Get(context.TODO(), "cron-1", metav1.GetOptions{})

the error message was

no kind "CronTab" is registered for version "stable.example.com/v1" in scheme "pkg/crd/typedClient/client/clientset/versioned/scheme/register.go:15"

however the kind CronTab has already been registered in register.go, not sure why it happened. is there anyone who can help on that? thanks.

[mhausenblas]

Thanks for raising this @yang-wang11 and I'm unsure I follow what exactly your steps were. You mentioned generate-groups.sh (I assume you're referring to https://github.com/kubernetes/code-generator?) Maybe @sttts has a better view?

[yang-wang11]

@mhausenblas @sttts yes, I follow the book step by step(chapter 4-5). I did the following changes:

1. upgrade to v1 instead of v1alpha1 for CRD
2. remove the sub-resource status for CRD

you may see below code generated from generate-groups.sh, it seems to look good.

var Scheme = runtime.NewScheme()
var Codecs = serializer.NewCodecFactory(Scheme)
var ParameterCodec = runtime.NewParameterCodec(Scheme)
var localSchemeBuilder = runtime.SchemeBuilder{
	stablev1.AddToScheme,
}
var AddToScheme = localSchemeBuilder.AddToScheme

func init() {
	v1.AddToGroupVersion(Scheme, schema.GroupVersion{Version: "v1"})
	utilruntime.Must(AddToScheme(Scheme))
}

I tried to force execute its init function. the error does seem not to disappear.

_ "typedClient/client/clientset/versioned/scheme"

[sttts]

Note the different spelling: CronTab vs. Crontab. The scheme has the latter, the clients wants the former.

[sttts]

no kind "CronTab" is registered for version "stable.example.com/v1" in scheme "pkg/crd/typedClient/client/clientset/versioned/scheme/register.go:15"

Is this a copy-and-pasted error message? Am not sure where client-gen gets the CronTab type from. It is based on the Go type, not the CRD yaml. Hence, it should print a "Crontab" error, not "CronTab" 🤔

[yang-wang11]

@sttts thanks for the help.
I'm a little confused, is that mean I need to rename my go type from Crontab to CronTab? like below

func addKnownTypes(scheme *runtime.Scheme) error {
	scheme.AddKnownTypes(SchemeGroupVersion,
		&CronTabList{},
		&CronTab{},
	)
	metav1.AddToGroupVersion(scheme, SchemeGroupVersion)
	return nil
}

[sttts]

If you add a type to a scheme, its Go type name is used as kind (via reflection).

Now I also understand what is going on. You are getting a CronTab from the server and the client tries to find a CronTab in its scheme. It only finds a Crontab, which is not helpful. So the server returns an unexpected object. Those two have to match.

Where Crontab is added to the scheme in register.go, you can give a custom name with the capital T. Then it will work too.

[yang-wang11]

no kind "CronTab" is registered for version "stable.example.com/v1" in scheme "pkg/crd/typedClient/client/clientset/versioned/scheme/register.go:15"

Is this a copy-and-pasted error message? Am not sure where client-gen gets the CronTab type from. It is based on the Go type, not the CRD yaml. Hence, it should print a "Crontab" error, not "CronTab" 🤔

yes, this error message copy from the console.

[yang-wang11]

@sttts @mhausenblas thanks for the help. it works.