## 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.

### Controllers overview

Below provides a high level overview of controllers in Istiod. For more information about each controller, consulting the controllers Go docs is recommended.

```mermaid
graph BT
    crd("CRD Watcher")
    subgraph Service Discovery
        ksd("Kubernetes Controller")
        sesd("Service Entry Controller")

		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()

  //
  // 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

// 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.

// 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.

	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",

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 {

- Migrated `pkg/controller/nodeipam/ipam/cloud_cidr_allocator.go, pkg/controller/nodeipam/ipam/multi_cidr_range_allocator.go pkg/controller/nodeipam/ipam/range_allocator.go pkg/controller/nodelifecycle/node_lifecycle_controller.go` to structured logging ([#112670](https://github.com/kubernetes/kubernetes/pull/112670), [@yangjunmyfm192085](https://github.com/yangjunmyfm192085))...

	"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"