Create/Get a custom kubernetes resource

Issue

I want to create a custom kubernetes resource with go. The application is deployed in the kubernetes cluster. I want to create e.g. the followng resource:

    apiVersion: configuration.konghq.com/v1
    kind: KongPlugin
    metadata:
      name: add-response-header
    config:
      add:
        headers:
        - "demo: injected-by-kong"
    plugin: response-transformer

So far I always created the ‘standard’ resources e.g. a secret with the following code:

     CreateSecret(name string, data map[string]string) error {
 confs, err := rest.InClusterConfig()
        if err != nil {
            panic(err)
        }
        clientset, err = kubernetes.NewForConfig(confs)
        i := clientset.CoreV1()
        if _, err := i.Secrets(namespace).Create(&v1.Secret{
            TypeMeta:   metav1.TypeMeta{
                Kind:       "Secret",
                APIVersion: "v1",
            },
            ObjectMeta: metav1.ObjectMeta{
                Name:   name,
            },
            StringData: data,
            Type:       "Opaque",
        }); err != nil {
            return err
        }
}

In addition I tried to get a resource with the following code:

b, err := clientset.RESTClient().Get().Namespace(namespace).Resource("KongPlugin").DoRaw()

I get the following err:

the server could not find the requested resource (get KongPlugin)

If I make a request at the command line k get KongPlugin I can see all the resources.

NAME                PLUGIN-TYPE           AGE
add-proxy-headers   request-transformer   3h34m

So how can view the custom resoources?

Solution

For RESTClient 👇🏼

Get:

You have to fully specify path to you custom resource.
Use fluent interface

data, err := clientset.RESTClient().
        Get().
        AbsPath("/apis/<api>/<version>").
        Namespace("<namespace>").
        Resource("kongplugins").
        Name("kongplugin-sample").
        DoRaw(context.TODO())

or specify manually

data, err := clientset.RESTClient().
        Get().
        AbsPath("/apis/<api>/<version>/namespaces/<namespace>/kongplugins/kongplugin-sample").
        DoRaw(context.TODO())

You can find AbsPath in selfLink of custom resource.

Create:

For example, you can post marshaled data use AbsPath

kongPlugin := &KongPlugin{
        TypeMeta: metav1.TypeMeta{
            APIVersion: "<api>/<version>",
            Kind:       "KongPlugin",
        },
        ObjectMeta: metav1.ObjectMeta{
            Name:      "kongplugin-sample",
            Namespace: "<namespace>",
        },
        ...}}

body, err := json.Marshal(kongPlugin)

data, err := clientset.RESTClient().
        Post().
        AbsPath("/apis/<api>/<version>/namespaces/<namespace>/kongplugins").
        Body(body).
        DoRaw(context.TODO())

because arg of the method Body(obj interface{}) is an empty interface, you can use different types of arguments according to documentation:
k8s.io/client-go/rest – func (*Request) Body

Answered By – kozmo

Answer Checked By – Robin (GoLangFix Admin)

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