How to access 3rd-party Custom Resource Definition?

Question

I am working on Opersator-SDK. In my operator controller, I try to create an Istio Custom resource -- virtualservices. The definition of virtualservices looks like as following:

kind: CustomResourceDefinition
apiVersion: apiextensions.k8s.io/v1beta1
metadata:
  name: virtualservices.networking.istio.io

Here I think there are a few of things that have to do first:

1. Get Istio API module
2. In my controller code, import istio virtualservices package
3. How to create/update virtualservice resource

My question is how to do them? Because I never do that before, so have to ask for help how to do that.

Answer 1

Here is an example of creating a istio virtual service using istio client-go. Here we are using istio.io/api/networking/v1alpha3 and istio.io/client-go/pkg/apis/networking/v1alpha3 to create the VirtualService custom resource spec. After that using istio.io/client-go/pkg/clientset/versioned to actually sending this spec to kubernetes API server.

package main

import (
    "context"
    "log"
    "os"

    v1alpha3Spec "istio.io/api/networking/v1alpha3"
    "istio.io/client-go/pkg/apis/networking/v1alpha3"
    versionedclient "istio.io/client-go/pkg/clientset/versioned"
    metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
    "k8s.io/client-go/tools/clientcmd"
)

func main() {

    kubeconfig := os.Getenv("KUBECONFIG")
    namespace := os.Getenv("NAMESPACE")

    if len(kubeconfig) == 0 || len(namespace) == 0 {
        log.Fatalf("Environment variables KUBECONFIG and NAMESPACE need to be set")
    }

    restConfig, err := clientcmd.BuildConfigFromFlags("", kubeconfig)
    if err != nil {
        log.Fatalf("Failed to create k8s rest client: %s", err)
    }

    ic, err := versionedclient.NewForConfig(restConfig)
    if err != nil {
        log.Fatalf("Failed to create istio client: %s", err)
    }
    var host []string
    host[0] = "abc.com"
    virtualServiceCrd := &v1alpha3.VirtualService{
        TypeMeta: metav1.TypeMeta{
            APIVersion: "networking.istio.io/v1alpha3",
            Kind:       "Virtualservice",
        },
        ObjectMeta: metav1.ObjectMeta{
            Name: "default",
        },
        Spec: v1alpha3Spec.VirtualService{
            Hosts: host,
        },
    }

    ic.NetworkingV1alpha3().VirtualServices(namespace).Create(context.TODO(), virtualServiceCrd, metav1.CreateOptions{})
}

Answer 2

import istio virtualservices package

Yes, you should import the Istio package, and every CRD is an api, so it comes with a client for "creating", "deleting", "updating" and "watching" programmatically using the library.

If you are using Golang, this is a good start: https://github.com/istio/client-go

And the api client: https://github.com/istio/client-go/tree/master/pkg