use watch instead of polling

README.md

@@ -10,9 +10,9 @@ and was created for lack of an alternative.
 
 ## How it works
 
-The controller simply gets all Pod Disruption Budgets for each namespace and
-compares them to Deployments and StatefulSets. For any resource with more than
-1 replica and no matching Pod Disruption Budget, a default PDB will be created:
+The controller uses Kubernetes informers and watch functionality to detect changes in Deployments, StatefulSets and PodDisruptionBudgets.
+It automatically gets all Pod Disruption Budgets for each namespace and compares them to Deployments and StatefulSets. 
+For any resource with more than 1 replica and no matching Pod Disruption Budget, a default PDB will be created:
 
 ```yaml
 apiVersion: policy/v1beta1

controller.go

@@ -7,13 +7,18 @@ import (
 	"time"
 
 	log "github.com/sirupsen/logrus"
+	appsv1 "k8s.io/api/apps/v1"
 	v1 "k8s.io/api/core/v1"
 	pv1 "k8s.io/api/policy/v1"
 	"k8s.io/apimachinery/pkg/api/equality"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/apimachinery/pkg/runtime"
 	"k8s.io/apimachinery/pkg/util/intstr"
+	"k8s.io/apimachinery/pkg/watch"
 	"k8s.io/client-go/kubernetes"
+	"k8s.io/client-go/tools/cache"
 	"k8s.io/client-go/util/retry"
+	"k8s.io/client-go/util/workqueue"
 )
 
 const (
@@ -32,81 +37,230 @@ var (
 // if missing.
 type PDBController struct {
 	kubernetes.Interface
-	interval           time.Duration
-	pdbNameSuffix      string
-	nonReadyTTL        time.Duration
-	parentResourceHash bool
-	maxUnavailable     intstr.IntOrString
+	interval            time.Duration // kept for backward compatibility
+	pdbNameSuffix       string
+	nonReadyTTL         time.Duration
+	parentResourceHash  bool
+	maxUnavailable      intstr.IntOrString
+	queue               workqueue.TypedRateLimitingInterface[string]
+	deploymentInformer  cache.SharedIndexInformer
+	statefulSetInformer cache.SharedIndexInformer
+	pdbInformer         cache.SharedIndexInformer
 }
 
 // NewPDBController initializes a new PDBController.
 func NewPDBController(interval time.Duration, client kubernetes.Interface, pdbNameSuffix string, nonReadyTTL time.Duration, parentResourceHash bool, maxUnavailable intstr.IntOrString) *PDBController {
-	return &PDBController{
+	log.Info("Initializing PDB controller with TypedRateLimitingInterface - v20250304")
+	controller := &PDBController{
 		Interface:          client,
 		interval:           interval,
 		pdbNameSuffix:      pdbNameSuffix,
 		nonReadyTTL:        nonReadyTTL,
 		parentResourceHash: parentResourceHash,
 		maxUnavailable:     maxUnavailable,
+		queue:              workqueue.NewTypedRateLimitingQueue(workqueue.DefaultTypedControllerRateLimiter[string]()),
 	}
-}
 
-// Run runs the controller loop until it receives a stop signal over the stop
-// channel.
-func (n *PDBController) Run(ctx context.Context) {
-	for {
-		log.Debug("Running main control loop.")
-		err := n.runOnce(ctx)
-		if err != nil {
-			log.Error(err)
-		}
+	// Setup Deployment informer
+	controller.deploymentInformer = cache.NewSharedIndexInformer(
+		&cache.ListWatch{
+			ListFunc: func(options metav1.ListOptions) (runtime.Object, error) {
+				return client.AppsV1().Deployments(v1.NamespaceAll).List(context.Background(), options)
+			},
+			WatchFunc: func(options metav1.ListOptions) (watch.Interface, error) {
+				return client.AppsV1().Deployments(v1.NamespaceAll).Watch(context.Background(), options)
+			},
+		},
+		&appsv1.Deployment{},
+		0, // resync disabled
+		cache.Indexers{cache.NamespaceIndex: cache.MetaNamespaceIndexFunc},
+	)
+
+	// Setup StatefulSet informer
+	controller.statefulSetInformer = cache.NewSharedIndexInformer(
+		&cache.ListWatch{
+			ListFunc: func(options metav1.ListOptions) (runtime.Object, error) {
+				return client.AppsV1().StatefulSets(v1.NamespaceAll).List(context.Background(), options)
+			},
+			WatchFunc: func(options metav1.ListOptions) (watch.Interface, error) {
+				return client.AppsV1().StatefulSets(v1.NamespaceAll).Watch(context.Background(), options)
+			},
+		},
+		&appsv1.StatefulSet{},
+		0, // resync disabled
+		cache.Indexers{cache.NamespaceIndex: cache.MetaNamespaceIndexFunc},
+	)
+
+	// Setup PodDisruptionBudget informer
+	controller.pdbInformer = cache.NewSharedIndexInformer(
+		&cache.ListWatch{
+			ListFunc: func(options metav1.ListOptions) (runtime.Object, error) {
+				return client.PolicyV1().PodDisruptionBudgets(v1.NamespaceAll).List(context.Background(), options)
+			},
+			WatchFunc: func(options metav1.ListOptions) (watch.Interface, error) {
+				return client.PolicyV1().PodDisruptionBudgets(v1.NamespaceAll).Watch(context.Background(), options)
+			},
+		},
+		&pv1.PodDisruptionBudget{},
+		0, // resync disabled
+		cache.Indexers{cache.NamespaceIndex: cache.MetaNamespaceIndexFunc},
+	)
+
+	// Setup event handlers
+	controller.deploymentInformer.AddEventHandler(cache.ResourceEventHandlerFuncs{
+		AddFunc: controller.enqueueResource,
+		UpdateFunc: func(old, new interface{}) {
+			controller.enqueueResource(new)
+		},
+		DeleteFunc: controller.enqueueResource,
+	})
 
-		select {
-		case <-time.After(n.interval):
-		case <-ctx.Done():
-			log.Info("Terminating main controller loop.")
-			return
-		}
-	}
+	controller.statefulSetInformer.AddEventHandler(cache.ResourceEventHandlerFuncs{
+		AddFunc: controller.enqueueResource,
+		UpdateFunc: func(old, new interface{}) {
+			controller.enqueueResource(new)
+		},
+		DeleteFunc: controller.enqueueResource,
+	})
+
+	controller.pdbInformer.AddEventHandler(cache.ResourceEventHandlerFuncs{
+		DeleteFunc: controller.enqueuePDB,
+	})
+
+	return controller
 }
 
-// runOnce runs the main reconcilation loop of the controller.
-func (n *PDBController) runOnce(ctx context.Context) error {
-	allPDBs, err := n.PolicyV1().PodDisruptionBudgets(v1.NamespaceAll).List(ctx, metav1.ListOptions{})
+func (n *PDBController) enqueueResource(obj interface{}) {
+	key, err := cache.MetaNamespaceKeyFunc(obj)
 	if err != nil {
-		return err
+		log.Errorf("Couldn't get key for object %+v: %v", obj, err)
+		return
+	}
+	n.queue.Add(key)
+}
+
+func (n *PDBController) enqueuePDB(obj interface{}) {
+	pdb, ok := obj.(*pv1.PodDisruptionBudget)
+	if !ok {
+		log.Errorf("Expected PodDisruptionBudget but got %+v", obj)
+		return
 	}
 
-	managedPDBs, unmanagedPDBs := filterPDBs(allPDBs.Items)
+	// Only enqueue for our managed PDBs
+	if !containLabels(pdb.Labels, ownerLabels) {
+		return
+	}
 
-	deployments, err := n.AppsV1().Deployments(v1.NamespaceAll).List(ctx, metav1.ListOptions{})
+	key, err := cache.MetaNamespaceKeyFunc(obj)
 	if err != nil {
-		return err
+		log.Errorf("Couldn't get key for object %+v: %v", obj, err)
+		return
+	}
+	n.queue.Add(key)
+}
+
+// Run runs the controller with the specified number of workers.
+func (n *PDBController) Run(ctx context.Context) {
+	defer n.queue.ShutDown()
+
+	log.Info("Starting PDB controller")
+
+	// Start the informers
+	go n.deploymentInformer.Run(ctx.Done())
+	go n.statefulSetInformer.Run(ctx.Done())
+	go n.pdbInformer.Run(ctx.Done())
+
+	// Wait for the caches to be synced
+	log.Info("Waiting for informer caches to sync")
+	if !cache.WaitForCacheSync(ctx.Done(),
+		n.deploymentInformer.HasSynced,
+		n.statefulSetInformer.HasSynced,
+		n.pdbInformer.HasSynced) {
+		log.Fatal("Failed to wait for caches to sync")
+		return
 	}
+	log.Info("Informer caches synced")
 
-	statefulSets, err := n.AppsV1().StatefulSets(v1.NamespaceAll).List(ctx, metav1.ListOptions{})
+	// Run the reconcile loop
+	go n.worker(ctx)
+
+	<-ctx.Done()
+	log.Info("Shutting down PDB controller")
+}
+
+func (n *PDBController) worker(ctx context.Context) {
+	for n.processNextItem(ctx) {
+	}
+}
+
+func (n *PDBController) processNextItem(ctx context.Context) bool {
+	key, quit := n.queue.Get()
+	if quit {
+		return false
+	}
+	defer n.queue.Done(key)
+
+	err := n.reconcile(ctx, key)
 	if err != nil {
-		return err
+		log.Errorf("Error processing item %s: %v", key, err)
+		n.queue.AddRateLimited(key)
+		return true
+	}
+
+	n.queue.Forget(key)
+	return true
+}
+
+func (n *PDBController) reconcile(ctx context.Context, key string) error {
+	log.Debugf("Processing key: %s", key)
+
+	// Process all resources and PDBs
+	return n.runOnce(ctx)
+}
+
+// runOnce runs the main reconcilation loop of the controller.
+func (n *PDBController) runOnce(ctx context.Context) error {
+	// Get all PDBs from the informer
+	var allPDBs []pv1.PodDisruptionBudget
+	for _, obj := range n.pdbInformer.GetStore().List() {
+		pdb, ok := obj.(*pv1.PodDisruptionBudget)
+		if !ok {
+			continue
+		}
+		allPDBs = append(allPDBs, *pdb)
 	}
 
-	resources := make([]kubeResource, 0, len(deployments.Items)+len(statefulSets.Items))
+	managedPDBs, unmanagedPDBs := filterPDBs(allPDBs)
 
-	for _, d := range deployments.Items {
+	// Get all resources from the informers
+	resources := make([]kubeResource, 0)
+
+	// Process Deployments
+	for _, obj := range n.deploymentInformer.GetStore().List() {
+		d, ok := obj.(*appsv1.Deployment)
+		if !ok {
+			continue
+		}
 		// manually set Kind and APIVersion because of a bug in
 		// client-go
 		// https://github.com/kubernetes/client-go/issues/308
 		d.Kind = "Deployment"
 		d.APIVersion = "apps/v1"
-		resources = append(resources, deployment{d})
+		resources = append(resources, deployment{*d})
 	}
 
-	for _, s := range statefulSets.Items {
+	// Process StatefulSets
+	for _, obj := range n.statefulSetInformer.GetStore().List() {
+		s, ok := obj.(*appsv1.StatefulSet)
+		if !ok {
+			continue
+		}
 		// manually set Kind and APIVersion because of a bug in
 		// client-go
 		// https://github.com/kubernetes/client-go/issues/308
 		s.Kind = "StatefulSet"
 		s.APIVersion = "apps/v1"
-		resources = append(resources, statefulSet{s})
+		resources = append(resources, statefulSet{*s})
 	}
 
 	desiredPDBs := n.generateDesiredPDBs(resources, managedPDBs, unmanagedPDBs)