Support scale to zero rabbitMQ

controllers/rabbitmqcluster_controller.go

@@ -201,9 +201,23 @@ func (r *RabbitmqClusterReconciler) Reconcile(ctx context.Context, req ctrl.Requ
 				if err := builder.Update(sts); err != nil {
 					return ctrl.Result{}, err
 				}
-				if r.scaleDown(ctx, rabbitmqCluster, current, sts) {
-					// return when cluster scale down detected; unsupported operation
-					return ctrl.Result{}, nil
+				if r.scaleToZero(current, sts) {
+					err := r.saveReplicasBeforeZero(ctx, rabbitmqCluster, current)
+					if err != nil {
+						return ctrl.Result{}, err
+					}
+				} else {
+					if r.scaleDown(ctx, rabbitmqCluster, current, sts) {
+						// return when cluster scale down detected; unsupported operation
+						return ctrl.Result{}, nil
+					}
+				}
+				if r.scaleFromZero(current, sts) {
+					if r.scaleFromZeroToBeforeReplicasConfigured(ctx, rabbitmqCluster, sts) {
+						// return when cluster scale down from zero detected; unsupported operation
+						return ctrl.Result{}, nil
+					}
+					r.removeReplicasBeforeZeroAnnotationIfExists(ctx, rabbitmqCluster)
 				}
 			}
 
@@ -213,7 +227,6 @@ func (r *RabbitmqClusterReconciler) Reconcile(ctx context.Context, req ctrl.Requ
 				return ctrl.Result{}, err
 			}
 		}
-
 		var operationResult controllerutil.OperationResult
 		err = clientretry.RetryOnConflict(clientretry.DefaultRetry, func() error {
 			var apiError error
@@ -249,9 +262,9 @@ func (r *RabbitmqClusterReconciler) Reconcile(ctx context.Context, req ctrl.Requ
 		}
 		return ctrl.Result{RequeueAfter: requeueAfter}, err
 	}
-
 	// Set ReconcileSuccess to true and update observedGeneration after all reconciliation steps have finished with no error
 	rabbitmqCluster.Status.ObservedGeneration = rabbitmqCluster.GetGeneration()
+
 	r.setReconcileSuccess(ctx, rabbitmqCluster, corev1.ConditionTrue, "Success", "Finish reconciling")
 
 	logger.Info("Finished reconciling")

controllers/reconcile_scale_zero.go

@@ -0,0 +1,95 @@
+package controllers
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"strconv"
+
+	ctrl "sigs.k8s.io/controller-runtime"
+
+	"github.com/rabbitmq/cluster-operator/v2/api/v1beta1"
+	"github.com/rabbitmq/cluster-operator/v2/internal/status"
+	appsv1 "k8s.io/api/apps/v1"
+	corev1 "k8s.io/api/core/v1"
+)
+
+const beforeZeroReplicasConfigured = "rabbitmq.com/before-zero-replicas-configured"
+
+// scaleToZero checks if the desired replicas is zero and the current replicas is not zero.
+func (r *RabbitmqClusterReconciler) scaleToZero(current, sts *appsv1.StatefulSet) bool {
+	currentReplicas := *current.Spec.Replicas
+	desiredReplicas := *sts.Spec.Replicas
+	return desiredReplicas == 0 && currentReplicas > 0
+}
+
+// scaleFromZero checks if the current replicas is zero and the desired replicas is greater than zero.
+func (r *RabbitmqClusterReconciler) scaleFromZero(current, sts *appsv1.StatefulSet) bool {
+	currentReplicas := *current.Spec.Replicas
+	desiredReplicas := *sts.Spec.Replicas
+	return currentReplicas == 0 && desiredReplicas > 0
+}
+
+// scaleDownFromZero checks if the current replicas is desired replicas would be greatter than replicas configured before zero state.
+func (r *RabbitmqClusterReconciler) scaleFromZeroToBeforeReplicasConfigured(ctx context.Context, cluster *v1beta1.RabbitmqCluster, sts *appsv1.StatefulSet) bool {
+	var err error
+	var beforeZeroReplicas int64
+	desiredReplicas := *sts.Spec.Replicas
+	annotationValue, ok := cluster.Annotations[beforeZeroReplicasConfigured]
+	if !ok {
+		return false
+	}
+
+	beforeZeroReplicas, err = strconv.ParseInt(annotationValue, 10, 32)
+	if err != nil {
+		msg := "Failed to convert string to integer for before-zero-replicas-configuration annotation"
+		reason := "TransformErrorOperation"
+		err = r.recordEventsAndSetCondition(ctx, cluster, status.ReconcileSuccess, corev1.ConditionFalse, corev1.EventTypeWarning, reason, msg)
+		if err != nil {
+			return true
+		}
+		return true
+	}
+	if desiredReplicas != int32(beforeZeroReplicas) {
+		msg := fmt.Sprintf("Unsupported operation; when scaling from zero, you can only restore the previous number of replicas (%d)", int32(beforeZeroReplicas))
+		reason := "UnsupportedOperation"
+		err = r.recordEventsAndSetCondition(ctx, cluster, status.ReconcileSuccess, corev1.ConditionFalse, corev1.EventTypeWarning, reason, msg)
+		if err != nil {
+			return true
+		}
+		return true
+	}
+	return false
+
+}
+
+// saveReplicasBeforeZero saves the current replicas count in an annotation before scaling down to zero.
+// This is used to prevent scaling down when the cluster change from zero replicas to a number less than the saved replicas count.
+func (r *RabbitmqClusterReconciler) saveReplicasBeforeZero(ctx context.Context, cluster *v1beta1.RabbitmqCluster, current *appsv1.StatefulSet) error {
+	var err error
+	currentReplicas := *current.Spec.Replicas
+	logger := ctrl.LoggerFrom(ctx)
+	msg := "Cluster Scale down to 0 replicas."
+	reason := "ScaleDownToZero"
+	logger.Info(msg)
+	err = r.updateAnnotation(ctx, cluster, cluster.Namespace, cluster.Name, beforeZeroReplicasConfigured, fmt.Sprint(currentReplicas))
+	r.Recorder.Event(cluster, corev1.EventTypeNormal, reason, msg)
+	return err
+}
+
+// If the annotation rabbitmq.com/before-zero-replicas-configured exists it will be deleted.
+func (r *RabbitmqClusterReconciler) removeReplicasBeforeZeroAnnotationIfExists(ctx context.Context, cluster *v1beta1.RabbitmqCluster) {
+	if _, ok := cluster.Annotations[beforeZeroReplicasConfigured]; ok {
+		r.deleteAnnotation(ctx, cluster, beforeZeroReplicasConfigured)
+	}
+}
+
+func (r *RabbitmqClusterReconciler) recordEventsAndSetCondition(ctx context.Context, cluster *v1beta1.RabbitmqCluster, condType status.RabbitmqClusterConditionType, condStatus corev1.ConditionStatus, eventType, reason, msg string) error {
+	logger := ctrl.LoggerFrom(ctx)
+	var statusErr error
+	logger.Error(errors.New(reason), msg)
+	r.Recorder.Event(cluster, eventType, reason, msg)
+	cluster.Status.SetCondition(condType, condStatus, reason, msg)
+	statusErr = r.Status().Update(ctx, cluster)
+	return statusErr
+}

controllers/reconcile_scale_zero_test.go

@@ -0,0 +1,231 @@
+package controllers_test
+
+import (
+	"context"
+	"fmt"
+
+	. "github.com/onsi/ginkgo/v2"
+	. "github.com/onsi/gomega"
+	rabbitmqv1beta1 "github.com/rabbitmq/cluster-operator/v2/api/v1beta1"
+	"github.com/rabbitmq/cluster-operator/v2/internal/status"
+	apierrors "k8s.io/apimachinery/pkg/api/errors"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/apimachinery/pkg/types"
+	"k8s.io/utils/ptr"
+	runtimeClient "sigs.k8s.io/controller-runtime/pkg/client"
+)
+
+var _ = Describe("Cluster scale to zero", func() {
+	var (
+		cluster          *rabbitmqv1beta1.RabbitmqCluster
+		defaultNamespace = "default"
+		ctx              = context.Background()
+	)
+
+	AfterEach(func() {
+		Expect(client.Delete(ctx, cluster)).To(Succeed())
+		waitForClusterDeletion(ctx, cluster, client)
+		Eventually(func() bool {
+			rmq := &rabbitmqv1beta1.RabbitmqCluster{}
+			err := client.Get(ctx, types.NamespacedName{Name: cluster.Name, Namespace: cluster.Namespace}, rmq)
+			return apierrors.IsNotFound(err)
+		}).Should(BeTrue())
+	})
+
+	It("scale to zero", func() {
+		By("update statefulSet replicas to zero", func() {
+			cluster = &rabbitmqv1beta1.RabbitmqCluster{
+				ObjectMeta: metav1.ObjectMeta{
+					Name:      "rabbitmq-to-zero",
+					Namespace: defaultNamespace,
+				},
+				Spec: rabbitmqv1beta1.RabbitmqClusterSpec{
+					Replicas: ptr.To(int32(2)),
+				},
+			}
+			Expect(client.Create(ctx, cluster)).To(Succeed())
+			waitForClusterCreation(ctx, cluster, client)
+
+			Expect(updateWithRetry(cluster, func(r *rabbitmqv1beta1.RabbitmqCluster) {
+				r.Spec.Replicas = ptr.To(int32(0))
+			})).To(Succeed())
+
+			Eventually(func() int32 {
+				sts, err := clientSet.AppsV1().StatefulSets(defaultNamespace).Get(ctx, cluster.ChildResourceName("server"), metav1.GetOptions{})
+				Expect(err).NotTo(HaveOccurred())
+				return *sts.Spec.Replicas
+			}, 10, 1).Should(Equal(int32(0)))
+
+		})
+
+		By("setting ReconcileSuccess to 'true'", func() {
+			Eventually(func() string {
+				rabbit := &rabbitmqv1beta1.RabbitmqCluster{}
+				Expect(client.Get(ctx, runtimeClient.ObjectKey{
+					Name:      cluster.Name,
+					Namespace: defaultNamespace,
+				}, rabbit)).To(Succeed())
+
+				for i := range rabbit.Status.Conditions {
+					if rabbit.Status.Conditions[i].Type == status.ReconcileSuccess {
+						return fmt.Sprintf(
+							"ReconcileSuccess status: %s, with reason: %s and message: %s",
+							rabbit.Status.Conditions[i].Status,
+							rabbit.Status.Conditions[i].Reason,
+							rabbit.Status.Conditions[i].Message)
+					}
+				}
+				return "ReconcileSuccess status: condition not present"
+			}, 0).Should(Equal("ReconcileSuccess status: True, " +
+				"with reason: Success " +
+				"and message: Finish reconciling"))
+		})
+	})
+})
+
+var _ = Describe("Cluster scale from zero", func() {
+	var (
+		cluster          *rabbitmqv1beta1.RabbitmqCluster
+		defaultNamespace = "default"
+		ctx              = context.Background()
+	)
+
+	AfterEach(func() {
+		Expect(client.Delete(ctx, cluster)).To(Succeed())
+		waitForClusterDeletion(ctx, cluster, client)
+		Eventually(func() bool {
+			rmq := &rabbitmqv1beta1.RabbitmqCluster{}
+			err := client.Get(ctx, types.NamespacedName{Name: cluster.Name, Namespace: cluster.Namespace}, rmq)
+			return apierrors.IsNotFound(err)
+		}).Should(BeTrue())
+	})
+
+	It("scale from zero", func() {
+		By("update statefulSet replicas from zero", func() {
+			cluster = &rabbitmqv1beta1.RabbitmqCluster{
+				ObjectMeta: metav1.ObjectMeta{
+					Name:      "rabbitmq-from-zero",
+					Namespace: defaultNamespace,
+					Annotations: map[string]string{
+						"rabbitmq.com/before-zero-replicas-configured": "2",
+					},
+				},
+				Spec: rabbitmqv1beta1.RabbitmqClusterSpec{
+					Replicas: ptr.To(int32(0)),
+				},
+			}
+			Expect(client.Create(ctx, cluster)).To(Succeed())
+			waitForClusterCreation(ctx, cluster, client)
+
+			Expect(updateWithRetry(cluster, func(r *rabbitmqv1beta1.RabbitmqCluster) {
+				r.Spec.Replicas = ptr.To(int32(2))
+			})).To(Succeed())
+
+			Eventually(func() int32 {
+				sts, err := clientSet.AppsV1().StatefulSets(defaultNamespace).Get(ctx, cluster.ChildResourceName("server"), metav1.GetOptions{})
+				Expect(err).NotTo(HaveOccurred())
+				return *sts.Spec.Replicas
+			}, 10, 1).Should(Equal(int32(2)))
+
+		})
+
+		By("setting ReconcileSuccess to 'true'", func() {
+			Eventually(func() string {
+				rabbit := &rabbitmqv1beta1.RabbitmqCluster{}
+				Expect(client.Get(ctx, runtimeClient.ObjectKey{
+					Name:      cluster.Name,
+					Namespace: defaultNamespace,
+				}, rabbit)).To(Succeed())
+
+				for i := range rabbit.Status.Conditions {
+					if rabbit.Status.Conditions[i].Type == status.ReconcileSuccess {
+						return fmt.Sprintf(
+							"ReconcileSuccess status: %s, with reason: %s and message: %s",
+							rabbit.Status.Conditions[i].Status,
+							rabbit.Status.Conditions[i].Reason,
+							rabbit.Status.Conditions[i].Message)
+					}
+				}
+				return "ReconcileSuccess status: condition not present"
+			}, 0).Should(Equal("ReconcileSuccess status: True, " +
+				"with reason: Success " +
+				"and message: Finish reconciling"))
+		})
+	})
+})
+
+var _ = Describe("Cluster scale from zero to less replicas configured", Ordered, func() {
+	var (
+		cluster          *rabbitmqv1beta1.RabbitmqCluster
+		defaultNamespace = "default"
+		ctx              = context.Background()
+	)
+
+	AfterEach(func() {
+		Expect(client.Delete(ctx, cluster)).To(Succeed())
+		waitForClusterDeletion(ctx, cluster, client)
+		Eventually(func() bool {
+			rmq := &rabbitmqv1beta1.RabbitmqCluster{}
+			err := client.Get(ctx, types.NamespacedName{Name: cluster.Name, Namespace: cluster.Namespace}, rmq)
+			return apierrors.IsNotFound(err)
+		}).Should(BeTrue())
+	})
+
+	It("scale from zero to less replicas", func() {
+		By("update statefulSet replicas from zero", func() {
+			cluster = &rabbitmqv1beta1.RabbitmqCluster{
+				ObjectMeta: metav1.ObjectMeta{
+					Name:      "rabbitmq-from-zero-to-less",
+					Namespace: defaultNamespace,
+					Annotations: map[string]string{
+						"rabbitmq.com/before-zero-replicas-configured": "2",
+					},
+				},
+				Spec: rabbitmqv1beta1.RabbitmqClusterSpec{
+					Replicas: ptr.To(int32(0)),
+				},
+			}
+			Expect(client.Create(ctx, cluster)).To(Succeed())
+			waitForClusterCreation(ctx, cluster, client)
+
+			Expect(updateWithRetry(cluster, func(r *rabbitmqv1beta1.RabbitmqCluster) {
+				r.Spec.Replicas = ptr.To(int32(1))
+			})).To(Succeed())
+
+			Consistently(func() int32 {
+				sts, err := clientSet.AppsV1().StatefulSets(defaultNamespace).Get(ctx, cluster.ChildResourceName("server"), metav1.GetOptions{})
+				Expect(err).NotTo(HaveOccurred())
+				return *sts.Spec.Replicas
+			}, 10, 1).Should(Equal(int32(0)))
+
+		})
+
+		By("setting 'Warning' events", func() {
+			Expect(aggregateEventMsgs(ctx, cluster, "UnsupportedOperation")).To(
+				ContainSubstring("Unsupported operation"))
+		})
+
+		By("setting ReconcileSuccess to 'false'", func() {
+			Eventually(func() string {
+				rabbit := &rabbitmqv1beta1.RabbitmqCluster{}
+				Expect(client.Get(ctx, runtimeClient.ObjectKey{
+					Name:      cluster.Name,
+					Namespace: defaultNamespace,
+				}, rabbit)).To(Succeed())
+
+				for i := range rabbit.Status.Conditions {
+					if rabbit.Status.Conditions[i].Type == status.ReconcileSuccess {
+						return fmt.Sprintf(
+							"ReconcileSuccess status: %s, with reason: %s and message: %s",
+							rabbit.Status.Conditions[i].Status,
+							rabbit.Status.Conditions[i].Reason,
+							rabbit.Status.Conditions[i].Message)
+					}
+				}
+				return "ReconcileSuccess status: condition not present"
+			}, 0).Should(Equal("ReconcileSuccess status: False, " +
+				"with reason: UnsupportedOperation " +
+				"and message: Unsupported operation; when scaling from zero, you can only restore the previous number of replicas (2)"))
+		})
+	})
+})

internal/status/all_replicas_ready.go

@@ -41,6 +41,13 @@ func AllReplicasReadyCondition(resources []runtime.Object,
 			if resource.Spec.Replicas != nil {
 				desiredReplicas = *resource.Spec.Replicas
 			}
+
+			if desiredReplicas == 0 {
+				condition.Status = corev1.ConditionFalse
+				condition.Reason = "ScaledToZero"
+				goto assignLastTransitionTime
+			}
+
 			if desiredReplicas == resource.Status.ReadyReplicas {
 				condition.Status = corev1.ConditionTrue
 				condition.Reason = "AllPodsAreReady"