## 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.

	if already {
		l.LogAndPrintf("Operator controller is already installed in %s namespace.", oiArgs.common.operatorNamespace)
		l.LogAndPrintf("Upgrading operator controller in namespace: %s using image: %s/operator:%s",
			oiArgs.common.operatorNamespace, oiArgs.common.hub, oiArgs.common.tag)
	} else {
		l.LogAndPrintf("Installing operator controller in namespace: %s using image: %s/operator:%s",

    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 }}

  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"]

  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{}

func operatorRemoveCmd(ctx cli.Context, rootArgs *RootArgs, orArgs *operatorRemoveArgs) *cobra.Command {
	return &cobra.Command{
		Use:   "remove",
		Short: "Removes the Istio operator controller from the cluster.",
		Long:  "The remove subcommand removes the Istio operator controller from the cluster.",
		Args: func(cmd *cobra.Command, args []string) error {
			if orArgs.revision == "" && !orArgs.purge {

  // If not specified, this will default to the time zone of the kube-controller-manager process.
  // The set of valid time zone names and the time zone offset is loaded from the system-wide time zone
  // database by the API server during CronJob validation and the controller manager during execution.
  // If no system-wide time zone database can be found a bundled version of the database is used instead.

  verbs: ["create", "get", "watch", "list", "update", "delete"]

# For status controller, so it can delete the distribution report configmap
- apiGroups: [""]
  resources: ["configmaps"]
  verbs: ["delete"]

# For gateway deployment controller
- apiGroups: ["coordination.k8s.io"]
  resources: ["leases"]

        apiVersions:
          - "*"
        resources:
          - "*"

    {{- if .Values.base.validationCABundle }}
    # Disable webhook controller in Pilot to stop patching it
    failurePolicy: Fail
    {{- else }}
    # Fail open until the validation webhook is ready. The webhook controller
    # will update this to `Fail` and patch in the `caBundle` when the webhook
    # endpoint is ready.
    failurePolicy: Ignore
    {{- end }}