Announcing Istio client-go

Getting programmatic access to Istio resources.

Nov 14, 2019 | By Neeraj Poddar - Aspen Mesh

We are pleased to announce the initial release of the Istio client go repository which enables developers to gain programmatic access to Istio APIs in a Kubernetes environment. The generated Kubernetes informers and client set in this repository makes it easy for developers to create controllers and perform Create, Read, Update and Delete (CRUD) operations for all Istio Custom Resource Definitions (CRDs).

This was a highly requested functionality by many Istio users, as is evident from the feature requests on the clients generated by Aspen Mesh and the Knative project. If you’re currently using one of the above mentioned clients, you can easily switch to using Istio client go like this:

import (
  - versionedclient ""
  + versionedclient ""

As the generated client sets are functionally equivalent, switching the imported client libraries should be sufficient in order to consume the newly generated library.

How to use client-go

The Istio client go repository follows the same branching strategy as the Istio API repository, as the client repository depends on the API definitions. If you want to use a stable client set, you can use the release branches or tagged versions in the client go repository. Using the client set is very similar to using the Kubernetes client go, here’s a quick example of using the client to list all Istio virtual services in the passed namespace:

package main

import (

  metav1 ""

  versionedclient ""

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)
  // Print all VirtualServices
  vsList, err := ic.NetworkingV1alpha3().VirtualServices(namespace).List(metav1.ListOptions{})
  if err != nil {
    log.Fatalf("Failed to get VirtualService in %s namespace: %s", namespace, err)
  for i := range vsList.Items {
    vs := vsList.Items[i]
    log.Printf("Index: %d VirtualService Hosts: %+v\n", i, vs.Spec.GetHosts())

You can find a more in-depth example here.

Useful tools created for generating Istio client-go

If you’re wondering why it took so long or why was it difficult to generate this client set, this section is for you. In Istio, we use protobuf specifications to write APIs which are then converted to Go definitions using the protobuf tool chain. There are three major challenges which you might face if you’re trying to generate Kubernetes client set from a protobuf-generated API:

I’m hoping that the newly released client library enables users to create more integrations and controllers for the Istio APIs, and the tools mentioned above can be used by developers to generate Kubernetes client set from Proto APIs.