## Writing Controllers

The `controllers` package offers a variety of helpers for writing controllers.
These operate in a similar manner as [`controller-runtime`](https://github.com/kubernetes-sigs/controller-runtime) but are *far* smaller and less abstract.

With a few exceptions, Istio controllers typically are split in two phases: construction and running.

		FieldSelector: strings.Join(fieldSelectors, ","),
	})
	c.queue = controllers.NewQueue("repair pods",
		controllers.WithReconciler(c.Reconcile),
		controllers.WithMaxAttempts(5))
	c.pods.AddEventHandler(controllers.ObjectHandler(c.queue.AddObject))

	return c, nil
}

func (c *Controller) Run(stop <-chan struct{}) {
	kube.WaitForCacheSync("repair controller", stop, c.pods.HasSynced)
	c.queue.Run(stop)
	c.pods.ShutdownHandlers()

    namespace: {{ .Values.global.istioNamespace }}
---
{{- if not (eq (toString .Values.pilot.env.PILOT_ENABLE_GATEWAY_API_DEPLOYMENT_CONTROLLER) "false") }}
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  name: istiod-gateway-controller{{- if not (eq .Values.revision "")}}-{{ .Values.revision }}{{- end }}-{{ .Release.Namespace }}
  labels:
    app: istiod
    release: {{ .Release.Name }}

  // replicas is the number of Pods created by the StatefulSet controller.
  optional int32 replicas = 2;

  // readyReplicas is the number of pods created by this StatefulSet controller with a Ready Condition.
  optional int32 readyReplicas = 3;

  // currentReplicas is the number of Pods created by the StatefulSet controller from the StatefulSet version
  // indicated by currentRevision.

// IngressClassSpec provides information about the class of an Ingress.
message IngressClassSpec {
  // controller refers to the name of the controller that should handle this
  // class. This allows for different "flavors" that are controlled by the
  // same controller. For example, you may have different parameters for the
  // same implementing controller. This should be specified as a
  // domain-prefixed path no more than 250 characters in length, e.g.

### Relationship between the CLI and controller

The CLI and controller share the same API and codebase for generating manifests from the API. You can think of the
controller as the CLI command `istioctl install` running in a loop in a pod in the cluster and using the config
from the in-cluster IstioOperator custom resource (CR).
There are two major differences:

  labels:
    app: istiod
    release: {{ .Release.Name }}
rules:
  # sidecar injection controller
  - apiGroups: ["admissionregistration.k8s.io"]
    resources: ["mutatingwebhookconfigurations"]
    verbs: ["get", "list", "watch", "update", "patch"]

  # configuration validation webhook controller
  - apiGroups: ["admissionregistration.k8s.io"]
    resources: ["validatingwebhookconfigurations"]

)

// OperatorCmd is a group of commands related to installation and management of the operator controller.
func OperatorCmd(ctx cli.Context) *cobra.Command {
	oc := &cobra.Command{
		Use:   "operator",
		Short: "Commands related to Istio operator controller.",
		Long:  "The operator command installs, dumps, removes and shows the status of the operator controller.",
	}

	odArgs := &operatorDumpArgs{}
	oiArgs := &operatorInitArgs{}

	"k8s.io/apimachinery/pkg/types"
	"k8s.io/client-go/kubernetes"
	"k8s.io/client-go/kubernetes/scheme"
	"sigs.k8s.io/controller-runtime/pkg/client"
	"sigs.k8s.io/controller-runtime/pkg/client/fake"
	"sigs.k8s.io/controller-runtime/pkg/client/interceptor"
	"sigs.k8s.io/controller-runtime/pkg/envtest"

	"istio.io/istio/istioctl/pkg/cli"
	"istio.io/istio/operator/pkg/apis/istio/v1alpha1"
	"istio.io/istio/operator/pkg/cache"

  //
  // More completion modes can be added in the future.
  // If the Job controller observes a mode that it doesn't recognize, which
  // is possible during upgrades due to version skew, the controller
  // skips updates for the Job.
  // +optional
  optional string completionMode = 9;

  // suspend specifies whether the Job controller should create Pods or not. If