Refactor all controllers to use shared watch helper functions

This change introduces a new shared helper pattern for all controllers to reduce
code duplication and improve maintainability. A new watch_helpers.go file provides
a generic CreateRequestsFromObjectUpdates function that encapsulates the common
pattern used across all seven designate controllers when handling watched resource
updates.

Each controller now implements a lightweight findXXXListObjects function specific
to its type and a requestsForObjectUpdates method that leverages the shared helper.
This approach returns only ObjectMeta instead of full objects, improving memory
efficiency. The old findObjectsForSrc methods have been completely removed across
all controllers, eliminating 222 lines of duplicated code.

All watch handlers now consistently use the new requestsForObjectUpdates method,
providing a uniform pattern that's easier to understand, maintain, and extend.
The refactoring covers DesignateAPI (with TLS field support), DesignateCentral,
DesignateProducer, DesignateMdns, DesignateBackendbind9, DesignateUnbound, and
DesignateWorker controllers.

This is purely a refactoring change with no functional differences. All controllers
pass fmt, vet, and linter checks. The net result is 38 fewer lines of code with
significantly improved consistency and maintainability that can serve as a template
for other operators in the openstack-k8s-operators ecosystem.

Co-authored-by: Cursor <[email protected]>

Author: beagles

controllers/designateapi_controller.go

@@ -59,6 +59,7 @@ import (
 	"github.com/openstack-k8s-operators/lib-common/modules/common/tls"
 	"github.com/openstack-k8s-operators/lib-common/modules/common/util"
 	mariadbv1 "github.com/openstack-k8s-operators/mariadb-operator/api/v1beta1"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 )
 
 // GetClient -
@@ -382,60 +383,52 @@ func (r *DesignateAPIReconciler) SetupWithManager(ctx context.Context, mgr ctrl.
 			handler.EnqueueRequestsFromMapFunc(svcSecretFn)).
 		Watches(
 			&corev1.Secret{},
-			handler.EnqueueRequestsFromMapFunc(r.findObjectsForSrc),
+			handler.EnqueueRequestsFromMapFunc(r.requestsForObjectUpdates),
 			builder.WithPredicates(predicate.ResourceVersionChangedPredicate{}),
 		).
 		Watches(&networkv1.NetworkAttachmentDefinition{},
 			handler.EnqueueRequestsFromMapFunc(nadFn)).
 		Watches(&topologyv1.Topology{},
-			handler.EnqueueRequestsFromMapFunc(r.findObjectsForSrc),
+			handler.EnqueueRequestsFromMapFunc(r.requestsForObjectUpdates),
 			builder.WithPredicates(predicate.GenerationChangedPredicate{})).
 		Watches(&keystonev1.KeystoneAPI{},
 			handler.EnqueueRequestsFromMapFunc(r.findObjectForSrc),
 			builder.WithPredicates(keystonev1.KeystoneAPIStatusChangedPredicate)).
 		Complete(r)
 }
 
-func (r *DesignateAPIReconciler) findObjectsForSrc(ctx context.Context, src client.Object) []reconcile.Request {
-	requests := []reconcile.Request{}
+// findAPIListObjects finds all DesignateAPI objects that reference the given source object
+// through a specific field. It returns only the ObjectMeta for matched objects to minimize memory usage.
+func findAPIListObjects(ctx context.Context, cl client.Client, field string, src client.Object, log *logr.Logger) ([]metav1.ObjectMeta, error) {
+	crList := &designatev1beta1.DesignateAPIList{}
+	err := cl.List(ctx, crList, &client.ListOptions{
+		FieldSelector: fields.OneTermEqualSelector(field, src.GetName()),
+		Namespace:     src.GetNamespace(),
+	})
+	if err != nil {
+		log.Error(err, fmt.Sprintf("listing %s for field: %s - %s", crList.GroupVersionKind().Kind, field, src.GetNamespace()))
+		return []metav1.ObjectMeta{}, err
+	}
+	items := make([]metav1.ObjectMeta, len(crList.Items))
+	for i, item := range crList.Items {
+		items[i] = item.ObjectMeta
+	}
+	return items, nil
+}
 
+// requestsForObjectUpdates creates reconcile requests for DesignateAPI objects that depend on
+// the given source object (e.g., a Secret or Topology). This method is used as a handler function
+// in the controller's watch setup.
+func (r *DesignateAPIReconciler) requestsForObjectUpdates(ctx context.Context, src client.Object) []reconcile.Request {
 	Log := r.GetLogger(ctx)
-
 	allWatchFields := []string{
 		passwordSecretField,
 		caBundleSecretNameField,
 		tlsAPIInternalField,
 		tlsAPIPublicField,
 		topologyField,
 	}
-
-	for _, field := range allWatchFields {
-		crList := &designatev1beta1.DesignateAPIList{}
-		listOps := &client.ListOptions{
-			FieldSelector: fields.OneTermEqualSelector(field, src.GetName()),
-			Namespace:     src.GetNamespace(),
-		}
-		err := r.List(context.TODO(), crList, listOps)
-		if err != nil {
-			Log.Error(err, fmt.Sprintf("listing %s for field: %s - %s", crList.GroupVersionKind().Kind, field, src.GetNamespace()))
-			return requests
-		}
-
-		for _, item := range crList.Items {
-			Log.Info(fmt.Sprintf("input source %s changed, reconcile: %s - %s", src.GetName(), item.GetName(), item.GetNamespace()))
-
-			requests = append(requests,
-				reconcile.Request{
-					NamespacedName: types.NamespacedName{
-						Name:      item.GetName(),
-						Namespace: item.GetNamespace(),
-					},
-				},
-			)
-		}
-	}
-
-	return requests
+	return CreateRequestsFromObjectUpdates(ctx, r.Client, src, allWatchFields, findAPIListObjects, &Log)
 }
 
 func (r *DesignateAPIReconciler) findObjectForSrc(ctx context.Context, src client.Object) []reconcile.Request {

controllers/designatebackendbind9_controller.go

@@ -52,6 +52,7 @@ import (
 	"github.com/openstack-k8s-operators/lib-common/modules/common/secret"
 	"github.com/openstack-k8s-operators/lib-common/modules/common/statefulset"
 	"github.com/openstack-k8s-operators/lib-common/modules/common/util"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 )
 
 // GetClient -
@@ -293,46 +294,39 @@ func (r *DesignateBackendbind9Reconciler) SetupWithManager(ctx context.Context,
 		Watches(&corev1.ConfigMap{},
 			handler.EnqueueRequestsFromMapFunc(configMapFn)).
 		Watches(&topologyv1.Topology{},
-			handler.EnqueueRequestsFromMapFunc(r.findObjectsForSrc),
+			handler.EnqueueRequestsFromMapFunc(r.requestsForObjectUpdates),
 			builder.WithPredicates(predicate.GenerationChangedPredicate{})).
 		Complete(r)
 }
 
-func (r *DesignateBackendbind9Reconciler) findObjectsForSrc(ctx context.Context, src client.Object) []reconcile.Request {
-	requests := []reconcile.Request{}
+// findBackendbind9ListObjects finds all DesignateBackendbind9 objects that reference the given source object
+// through a specific field. It returns only the ObjectMeta for matched objects to minimize memory usage.
+func findBackendbind9ListObjects(ctx context.Context, cl client.Client, field string, src client.Object, log *logr.Logger) ([]metav1.ObjectMeta, error) {
+	crList := &designatev1beta1.DesignateBackendbind9List{}
+	err := cl.List(ctx, crList, &client.ListOptions{
+		FieldSelector: fields.OneTermEqualSelector(field, src.GetName()),
+		Namespace:     src.GetNamespace(),
+	})
+	if err != nil {
+		log.Error(err, fmt.Sprintf("listing %s for field: %s - %s", crList.GroupVersionKind().Kind, field, src.GetNamespace()))
+		return []metav1.ObjectMeta{}, err
+	}
+	items := make([]metav1.ObjectMeta, len(crList.Items))
+	for i, item := range crList.Items {
+		items[i] = item.ObjectMeta
+	}
+	return items, nil
+}
 
+// requestsForObjectUpdates creates reconcile requests for DesignateBackendbind9 objects that depend on
+// the given source object (e.g., a Topology). This method is used as a handler function
+// in the controller's watch setup.
+func (r *DesignateBackendbind9Reconciler) requestsForObjectUpdates(ctx context.Context, src client.Object) []reconcile.Request {
 	Log := r.GetLogger(ctx)
-
 	allWatchFields := []string{
 		topologyField,
 	}
-
-	for _, field := range allWatchFields {
-		crList := &designatev1beta1.DesignateBackendbind9List{}
-		listOps := &client.ListOptions{
-			FieldSelector: fields.OneTermEqualSelector(field, src.GetName()),
-			Namespace:     src.GetNamespace(),
-		}
-		err := r.List(context.TODO(), crList, listOps)
-		if err != nil {
-			Log.Error(err, fmt.Sprintf("listing %s for field: %s - %s", crList.GroupVersionKind().Kind, field, src.GetNamespace()))
-			return requests
-		}
-
-		for _, item := range crList.Items {
-			Log.Info(fmt.Sprintf("input source %s changed, reconcile: %s - %s", src.GetName(), item.GetName(), item.GetNamespace()))
-
-			requests = append(requests,
-				reconcile.Request{
-					NamespacedName: types.NamespacedName{
-						Name:      item.GetName(),
-						Namespace: item.GetNamespace(),
-					},
-				},
-			)
-		}
-	}
-	return requests
+	return CreateRequestsFromObjectUpdates(ctx, r.Client, src, allWatchFields, findBackendbind9ListObjects, &Log)
 }
 
 func (r *DesignateBackendbind9Reconciler) reconcileDelete(ctx context.Context, instance *designatev1beta1.DesignateBackendbind9, helper *helper.Helper) (ctrl.Result, error) {

controllers/designatecentral_controller.go

@@ -52,6 +52,7 @@ import (
 	"github.com/openstack-k8s-operators/lib-common/modules/common/tls"
 	"github.com/openstack-k8s-operators/lib-common/modules/common/util"
 	mariadbv1 "github.com/openstack-k8s-operators/mariadb-operator/api/v1beta1"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 )
 
 // GetClient -
@@ -332,54 +333,46 @@ func (r *DesignateCentralReconciler) SetupWithManager(ctx context.Context, mgr c
 			handler.EnqueueRequestsFromMapFunc(svcSecretFn)).
 		Watches(
 			&corev1.Secret{},
-			handler.EnqueueRequestsFromMapFunc(r.findObjectsForSrc),
+			handler.EnqueueRequestsFromMapFunc(r.requestsForObjectUpdates),
 			builder.WithPredicates(predicate.ResourceVersionChangedPredicate{}),
 		).
 		// watch the config CMs we don't own
 		Watches(&topologyv1.Topology{},
-			handler.EnqueueRequestsFromMapFunc(r.findObjectsForSrc),
+			handler.EnqueueRequestsFromMapFunc(r.requestsForObjectUpdates),
 			builder.WithPredicates(predicate.GenerationChangedPredicate{})).
 		Complete(r)
 }
 
-func (r *DesignateCentralReconciler) findObjectsForSrc(ctx context.Context, src client.Object) []reconcile.Request {
-	requests := []reconcile.Request{}
+// findCentralListObjects finds all DesignateCentral objects that reference the given source object
+// through a specific field. It returns only the ObjectMeta for matched objects to minimize memory usage.
+func findCentralListObjects(ctx context.Context, cl client.Client, field string, src client.Object, log *logr.Logger) ([]metav1.ObjectMeta, error) {
+	crList := &designatev1beta1.DesignateCentralList{}
+	err := cl.List(ctx, crList, &client.ListOptions{
+		FieldSelector: fields.OneTermEqualSelector(field, src.GetName()),
+		Namespace:     src.GetNamespace(),
+	})
+	if err != nil {
+		log.Error(err, fmt.Sprintf("listing %s for field: %s - %s", crList.GroupVersionKind().Kind, field, src.GetNamespace()))
+		return []metav1.ObjectMeta{}, err
+	}
+	items := make([]metav1.ObjectMeta, len(crList.Items))
+	for i, item := range crList.Items {
+		items[i] = item.ObjectMeta
+	}
+	return items, nil
+}
 
+// requestsForObjectUpdates creates reconcile requests for DesignateCentral objects that depend on
+// the given source object (e.g., a Secret or Topology). This method is used as a handler function
+// in the controller's watch setup.
+func (r *DesignateCentralReconciler) requestsForObjectUpdates(ctx context.Context, src client.Object) []reconcile.Request {
 	Log := r.GetLogger(ctx)
-
 	allWatchFields := []string{
 		passwordSecretField,
 		caBundleSecretNameField,
 		topologyField,
 	}
-
-	for _, field := range allWatchFields {
-		crList := &designatev1beta1.DesignateCentralList{}
-		listOps := &client.ListOptions{
-			FieldSelector: fields.OneTermEqualSelector(field, src.GetName()),
-			Namespace:     src.GetNamespace(),
-		}
-		err := r.List(context.TODO(), crList, listOps)
-		if err != nil {
-			Log.Error(err, fmt.Sprintf("listing %s for field: %s - %s", crList.GroupVersionKind().Kind, field, src.GetNamespace()))
-			return requests
-		}
-
-		for _, item := range crList.Items {
-			Log.Info(fmt.Sprintf("input source %s changed, reconcile: %s - %s", src.GetName(), item.GetName(), item.GetNamespace()))
-
-			requests = append(requests,
-				reconcile.Request{
-					NamespacedName: types.NamespacedName{
-						Name:      item.GetName(),
-						Namespace: item.GetNamespace(),
-					},
-				},
-			)
-		}
-	}
-
-	return requests
+	return CreateRequestsFromObjectUpdates(ctx, r.Client, src, allWatchFields, findCentralListObjects, &Log)
 }
 
 func (r *DesignateCentralReconciler) reconcileDelete(ctx context.Context, instance *designatev1beta1.DesignateCentral, helper *helper.Helper) (ctrl.Result, error) {

controllers/designatemdns_controller.go

@@ -54,6 +54,7 @@ import (
 	"github.com/openstack-k8s-operators/lib-common/modules/common/tls"
 	"github.com/openstack-k8s-operators/lib-common/modules/common/util"
 	mariadbv1 "github.com/openstack-k8s-operators/mariadb-operator/api/v1beta1"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 )
 
 // GetClient -
@@ -337,56 +338,48 @@ func (r *DesignateMdnsReconciler) SetupWithManager(ctx context.Context, mgr ctrl
 			handler.EnqueueRequestsFromMapFunc(svcSecretFn)).
 		Watches(
 			&corev1.Secret{},
-			handler.EnqueueRequestsFromMapFunc(r.findObjectsForSrc),
+			handler.EnqueueRequestsFromMapFunc(r.requestsForObjectUpdates),
 			builder.WithPredicates(predicate.ResourceVersionChangedPredicate{}),
 		).
 		// watch the config CMs we don't own
 		Watches(&corev1.ConfigMap{},
 			handler.EnqueueRequestsFromMapFunc(configMapFn)).
 		Watches(&topologyv1.Topology{},
-			handler.EnqueueRequestsFromMapFunc(r.findObjectsForSrc),
+			handler.EnqueueRequestsFromMapFunc(r.requestsForObjectUpdates),
 			builder.WithPredicates(predicate.GenerationChangedPredicate{})).
 		Complete(r)
 }
 
-func (r *DesignateMdnsReconciler) findObjectsForSrc(ctx context.Context, src client.Object) []reconcile.Request {
-	requests := []reconcile.Request{}
+// findMdnsListObjects finds all DesignateMdns objects that reference the given source object
+// through a specific field. It returns only the ObjectMeta for matched objects to minimize memory usage.
+func findMdnsListObjects(ctx context.Context, cl client.Client, field string, src client.Object, log *logr.Logger) ([]metav1.ObjectMeta, error) {
+	crList := &designatev1beta1.DesignateMdnsList{}
+	err := cl.List(ctx, crList, &client.ListOptions{
+		FieldSelector: fields.OneTermEqualSelector(field, src.GetName()),
+		Namespace:     src.GetNamespace(),
+	})
+	if err != nil {
+		log.Error(err, fmt.Sprintf("listing %s for field: %s - %s", crList.GroupVersionKind().Kind, field, src.GetNamespace()))
+		return []metav1.ObjectMeta{}, err
+	}
+	items := make([]metav1.ObjectMeta, len(crList.Items))
+	for i, item := range crList.Items {
+		items[i] = item.ObjectMeta
+	}
+	return items, nil
+}
 
+// requestsForObjectUpdates creates reconcile requests for DesignateMdns objects that depend on
+// the given source object (e.g., a Secret or Topology). This method is used as a handler function
+// in the controller's watch setup.
+func (r *DesignateMdnsReconciler) requestsForObjectUpdates(ctx context.Context, src client.Object) []reconcile.Request {
 	Log := r.GetLogger(ctx)
-
 	allWatchFields := []string{
 		passwordSecretField,
 		caBundleSecretNameField,
 		topologyField,
 	}
-
-	for _, field := range allWatchFields {
-		crList := &designatev1beta1.DesignateMdnsList{}
-		listOps := &client.ListOptions{
-			FieldSelector: fields.OneTermEqualSelector(field, src.GetName()),
-			Namespace:     src.GetNamespace(),
-		}
-		err := r.List(context.TODO(), crList, listOps)
-		if err != nil {
-			Log.Error(err, fmt.Sprintf("listing %s for field: %s - %s", crList.GroupVersionKind().Kind, field, src.GetNamespace()))
-			return requests
-		}
-
-		for _, item := range crList.Items {
-			Log.Info(fmt.Sprintf("input source %s changed, reconcile: %s - %s", src.GetName(), item.GetName(), item.GetNamespace()))
-
-			requests = append(requests,
-				reconcile.Request{
-					NamespacedName: types.NamespacedName{
-						Name:      item.GetName(),
-						Namespace: item.GetNamespace(),
-					},
-				},
-			)
-		}
-	}
-
-	return requests
+	return CreateRequestsFromObjectUpdates(ctx, r.Client, src, allWatchFields, findMdnsListObjects, &Log)
 }
 
 func (r *DesignateMdnsReconciler) reconcileDelete(ctx context.Context, instance *designatev1beta1.DesignateMdns, helper *helper.Helper) (ctrl.Result, error) {