Only allow 1 replica of Reaper's STS

apis/reaper/v1alpha1/reaper_types.go

@@ -29,6 +29,8 @@ import (
 // EDIT THIS FILE!  THIS IS SCAFFOLDING FOR YOU TO OWN!
 // NOTE: json tags are required.  Any new fields you add must have json tags for the fields to be serialized.
 
+var SingleReplica = int32(1)
+
 const (
 	ReaperLabel          = "k8ssandra.io/reaper"
 	DefaultKeyspace      = "reaper_db"

controllers/reaper/reaper_controller.go

@@ -33,6 +33,7 @@ import (
 	"k8s.io/apimachinery/pkg/runtime"
 	"k8s.io/apimachinery/pkg/types"
 	"k8s.io/utils/ptr"
+	"math"
 	ctrl "sigs.k8s.io/controller-runtime"
 	"sigs.k8s.io/controller-runtime/pkg/builder"
 	"sigs.k8s.io/controller-runtime/pkg/client"
@@ -244,6 +245,20 @@ func (r *ReaperReconciler) reconcileDeployment(
 		return ctrl.Result{}, nil
 	}
 
+	// if using memory storage, we need to ensure only one Reaper exists ~ the STS has at most 1 replica
+	if actualReaper.Spec.StorageType == reaperapi.StorageTypeMemory {
+		desiredReplicas := getDeploymentReplicas(desiredDeployment, logger)
+		if desiredReplicas > 1 {
+			logger.Info(fmt.Sprintf("reaper with memory storage can only have one replica, not allowing the %d that are desired", desiredReplicas))
+			setDeploymentReplicas(&desiredDeployment, &reaperapi.SingleReplica, logger)
+		}
+		actualReplicas := getDeploymentReplicas(actualDeployment, logger)
+		if actualReplicas > 1 {
+			logger.Info(fmt.Sprintf("reaper with memory storage currently has %d replicas, scaling down to 1", actualReplicas))
+			setDeploymentReplicas(&desiredDeployment, &reaperapi.SingleReplica, logger)
+		}
+	}
+
 	// Check if the deployment needs to be updated
 	if !annotations.CompareHashAnnotations(actualDeployment, desiredDeployment) {
 		logger.Info("Updating Reaper Deployment")
@@ -276,6 +291,29 @@ func (r *ReaperReconciler) reconcileDeployment(
 	return ctrl.Result{}, nil
 }
 
+func getDeploymentReplicas(actualDeployment client.Object, logger logr.Logger) int32 {
+	switch actual := actualDeployment.(type) {
+	case *appsv1.Deployment:
+		return *actual.Spec.Replicas
+	case *appsv1.StatefulSet:
+		return *actual.Spec.Replicas
+	default:
+		logger.Error(fmt.Errorf("unexpected type %T", actualDeployment), "Failed to get deployment replicas")
+		return math.MaxInt32
+	}
+}
+
+func setDeploymentReplicas(desiredDeployment *client.Object, singleReplica *int32, logger logr.Logger) {
+	switch desired := (*desiredDeployment).(type) {
+	case *appsv1.Deployment:
+		desired.Spec.Replicas = singleReplica
+	case *appsv1.StatefulSet:
+		desired.Spec.Replicas = singleReplica
+	default:
+		logger.Error(fmt.Errorf("unexpected type %T", desiredDeployment), "Failed to set deployment replicas")
+	}
+}
+
 func (r *ReaperReconciler) reconcileService(
 	ctx context.Context,
 	actualReaper *reaperapi.Reaper,

pkg/reaper/deployment.go

@@ -326,7 +326,7 @@ func computeVolumeClaims(reaper *api.Reaper) []corev1.PersistentVolumeClaim {
 
 	var volumeClaimsPec *corev1.PersistentVolumeClaimSpec
 	storageClass := api.DefaultStorageClass
-	accessModes := []corev1.PersistentVolumeAccessMode{corev1.ReadWriteOnce}
+	accessModes := []corev1.PersistentVolumeAccessMode{api.DefaultAccessMode}
 	if reaper.Spec.StorageConfig != nil {
 		volumeClaimsPec = reaper.Spec.StorageConfig.DeepCopy()
 		if volumeClaimsPec.Resources.Requests.Storage() == nil {
@@ -373,6 +373,7 @@ func NewStatefulSet(reaper *api.Reaper, dc *cassdcapi.CassandraDatacenter, logge
 				Spec:       computePodSpec(reaper, dc, nil, nil, nil),
 			},
 			VolumeClaimTemplates: computeVolumeClaims(reaper),
+			Replicas:             &api.SingleReplica,
 		},
 	}
 	addAuthEnvVars(&statefulSet.Spec.Template, authVars)