Verify PVCs are not used by any Pods before deleting them

CHANGELOG.md

@@ -11,6 +11,8 @@ Changelog for Cass Operator, new PRs should update the `main / unreleased` secti
 
 ## unreleased
 
+* [ENHANCEMENT] [#737](https://github.com/k8ssandra/cass-operator/issues/737) Before issuing PVC deletion when deleting a datacenter, verify the PVCs that match the labels are not actually used by any pods.
+
 ## v1.23.0
 
 * [CHANGE] [#720](https://github.com/k8ssandra/cass-operator/issues/720) Always use ObjectMeta.Name for the PodDisruptionBudget resource name, not the DatacenterName

cmd/main.go

@@ -26,11 +26,13 @@ import (
 	"go.uber.org/zap/zapcore"
 	_ "k8s.io/client-go/plugin/pkg/client/auth"
 
+	corev1 "k8s.io/api/core/v1"
 	"k8s.io/apimachinery/pkg/runtime"
 	utilruntime "k8s.io/apimachinery/pkg/util/runtime"
 	clientgoscheme "k8s.io/client-go/kubernetes/scheme"
 	ctrl "sigs.k8s.io/controller-runtime"
 	"sigs.k8s.io/controller-runtime/pkg/cache"
+	"sigs.k8s.io/controller-runtime/pkg/client"
 	"sigs.k8s.io/controller-runtime/pkg/healthz"
 	"sigs.k8s.io/controller-runtime/pkg/log/zap"
 
@@ -119,6 +121,8 @@ func main() {
 		os.Exit(1)
 	}
 
+	ctx := ctrl.SetupSignalHandler()
+
 	if err = (&controllers.CassandraDatacenterReconciler{
 		Client:   mgr.GetClient(),
 		Log:      ctrl.Log.WithName("controllers").WithName("CassandraDatacenter"),
@@ -143,6 +147,24 @@ func main() {
 		os.Exit(1)
 	}
 
+	if err := mgr.GetCache().IndexField(ctx, &corev1.Pod{}, "spec.volumes.persistentVolumeClaim.claimName", func(obj client.Object) []string {
+		pod, ok := obj.(*corev1.Pod)
+		if !ok {
+			return nil
+		}
+
+		var pvcNames []string
+		for _, volume := range pod.Spec.Volumes {
+			if volume.PersistentVolumeClaim != nil {
+				pvcNames = append(pvcNames, volume.PersistentVolumeClaim.ClaimName)
+			}
+		}
+		return pvcNames
+	}); err != nil {
+		setupLog.Error(err, "unable to set up field indexer")
+		os.Exit(1)
+	}
+
 	if err := mgr.AddHealthzCheck("healthz", healthz.Ping); err != nil {
 		setupLog.Error(err, "unable to set up health check")
 		os.Exit(1)
@@ -153,7 +175,7 @@ func main() {
 	}
 
 	setupLog.Info("starting manager")
-	if err := mgr.Start(ctrl.SetupSignalHandler()); err != nil {
+	if err := mgr.Start(ctx); err != nil {
 		setupLog.Error(err, "problem running manager")
 		os.Exit(1)
 	}

internal/controllers/cassandra/suite_test.go

@@ -28,6 +28,7 @@ import (
 	. "github.com/onsi/ginkgo/v2"
 	. "github.com/onsi/gomega"
 	"go.uber.org/zap/zapcore"
+	corev1 "k8s.io/api/core/v1"
 	"k8s.io/client-go/kubernetes/scheme"
 	ctrl "sigs.k8s.io/controller-runtime"
 	"sigs.k8s.io/controller-runtime/pkg/client"
@@ -97,7 +98,7 @@ var _ = BeforeSuite(func() {
 	Expect(err).ToNot(HaveOccurred())
 
 	err = (&CassandraDatacenterReconciler{
-		Client:   k8sClient,
+		Client:   k8sManager.GetClient(),
 		Log:      ctrl.Log.WithName("controllers").WithName("CassandraDatacenter"),
 		Scheme:   k8sManager.GetScheme(),
 		Recorder: k8sManager.GetEventRecorderFor("cass-operator"),
@@ -116,6 +117,21 @@ var _ = BeforeSuite(func() {
 	}).SetupWithManager(k8sManager)
 	Expect(err).ToNot(HaveOccurred())
 
+	Expect(k8sManager.GetCache().IndexField(ctx, &corev1.Pod{}, "spec.volumes.persistentVolumeClaim.claimName", func(obj client.Object) []string {
+		pod, ok := obj.(*corev1.Pod)
+		if !ok {
+			return nil
+		}
+
+		var pvcNames []string
+		for _, volume := range pod.Spec.Volumes {
+			if volume.PersistentVolumeClaim != nil {
+				pvcNames = append(pvcNames, volume.PersistentVolumeClaim.ClaimName)
+			}
+		}
+		return pvcNames
+	})).ToNot(HaveOccurred())
+
 	// Reduce the polling times and sleeps to speed up the tests
 	cooldownPeriod = 1 * time.Millisecond
 	minimumRequeueTime = 10 * time.Millisecond

internal/envtest/statefulset_controller.go

@@ -80,7 +80,7 @@ func (r *StatefulSetReconciler) Reconcile(ctx context.Context, req ctrl.Request)
 	// TODO Get existing pods and modify them .
 
 	podList := &corev1.PodList{}
-	if err := r.Client.List(ctx, podList, client.MatchingLabels(sts.Spec.Template.Labels), client.InNamespace(req.Namespace)); err != nil {
+	if err := r.Client.List(ctx, podList, client.MatchingLabels(sts.Labels), client.InNamespace(req.Namespace)); err != nil {
 		logger.Error(err, "Failed to list the pods belonging to this StatefulSet")
 		return ctrl.Result{}, err
 	}
@@ -94,7 +94,7 @@ func (r *StatefulSetReconciler) Reconcile(ctx context.Context, req ctrl.Request)
 
 	if len(stsPods) > intendedReplicas {
 		// We need to delete the pods..
-		for i := len(stsPods) - 1; i > intendedReplicas; i-- {
+		for i := len(stsPods) - 1; i >= intendedReplicas; i-- {
 			pod := stsPods[i]
 			if err := r.Client.Delete(ctx, pod); err != nil {
 				logger.Error(err, "Failed to delete extra pod from this StS")

pkg/reconciliation/handler_test.go

@@ -5,16 +5,19 @@ package reconciliation
 
 import (
 	"fmt"
+	"strings"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/mock"
 
-	v1 "k8s.io/api/core/v1"
+	appsv1 "k8s.io/api/apps/v1"
+	corev1 "k8s.io/api/core/v1"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
 	"k8s.io/utils/ptr"
 
+	"sigs.k8s.io/controller-runtime/pkg/client"
 	"sigs.k8s.io/controller-runtime/pkg/controller/controllerutil"
 	"sigs.k8s.io/controller-runtime/pkg/reconcile"
 
@@ -91,16 +94,33 @@ func TestProcessDeletion_FailedDelete(t *testing.T) {
 
 	mockClient := mocks.NewClient(t)
 	rc.Client = mockClient
+	rc.Datacenter.Spec.Size = 0
 
 	k8sMockClientList(mockClient, nil).
 		Run(func(args mock.Arguments) {
-			arg := args.Get(1).(*v1.PersistentVolumeClaimList)
-			arg.Items = []v1.PersistentVolumeClaim{{
+			_, ok := args.Get(1).(*corev1.PodList)
+			if ok {
+				if strings.HasPrefix(args.Get(2).(*client.ListOptions).FieldSelector.String(), "spec.volumes.persistentVolumeClaim.claimName") {
+					arg := args.Get(1).(*corev1.PodList)
+					arg.Items = []corev1.Pod{}
+				} else {
+					t.Fail()
+				}
+				return
+			}
+			arg := args.Get(1).(*corev1.PersistentVolumeClaimList)
+			arg.Items = []corev1.PersistentVolumeClaim{{
 				ObjectMeta: metav1.ObjectMeta{
 					Name: "pvc-1",
 				},
 			}}
-		})
+		}).Twice()
+
+	k8sMockClientGet(mockClient, nil).
+		Run(func(args mock.Arguments) {
+			arg := args.Get(2).(*appsv1.StatefulSet)
+			arg.Spec.Replicas = ptr.To[int32](0)
+		}).Once()
 
 	k8sMockClientDelete(mockClient, fmt.Errorf(""))
 
@@ -131,16 +151,31 @@ func TestProcessDeletion(t *testing.T) {
 
 	k8sMockClientList(mockClient, nil).
 		Run(func(args mock.Arguments) {
-			arg := args.Get(1).(*v1.PersistentVolumeClaimList)
-			arg.Items = []v1.PersistentVolumeClaim{{
+			_, ok := args.Get(1).(*corev1.PodList)
+			if ok {
+				if strings.HasPrefix(args.Get(2).(*client.ListOptions).FieldSelector.String(), "spec.volumes.persistentVolumeClaim.claimName") {
+					arg := args.Get(1).(*corev1.PodList)
+					arg.Items = []corev1.Pod{}
+				} else {
+					t.Fail()
+				}
+				return
+			}
+			arg := args.Get(1).(*corev1.PersistentVolumeClaimList)
+			arg.Items = []corev1.PersistentVolumeClaim{{
 				ObjectMeta: metav1.ObjectMeta{
 					Name: "pvc-1",
 				},
 			}}
-		}) // ListPods
+		}).Twice() // ListPods
 
 	k8sMockClientDelete(mockClient, nil) // Delete PVC
 	k8sMockClientUpdate(mockClient, nil) // Remove dc finalizer
+	k8sMockClientGet(mockClient, nil).
+		Run(func(args mock.Arguments) {
+			arg := args.Get(2).(*appsv1.StatefulSet)
+			arg.Spec.Replicas = ptr.To[int32](0)
+		}).Once()
 
 	emptySecretWatcher(t, rc)
 

pkg/reconciliation/reconcile_datacenter.go

@@ -13,6 +13,7 @@ import (
 	storagev1 "k8s.io/api/storage/v1"
 	"k8s.io/apimachinery/pkg/api/errors"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/apimachinery/pkg/fields"
 	"k8s.io/apimachinery/pkg/labels"
 	"k8s.io/apimachinery/pkg/types"
 	"sigs.k8s.io/controller-runtime/pkg/client"
@@ -76,6 +77,30 @@ func (rc *ReconciliationContext) ProcessDeletion() result.ReconcileResult {
 			// How could we have pods if we've decommissioned everything?
 			return result.RequeueSoon(5)
 		}
+	} else {
+		// This is small mini reconcile to make everything 0 sized before we finish deletion, but do not run decommission in Cassandra
+		rc.ReqLogger.Info("Proceeding with deletion, setting all StatefulSets to 0 replicas")
+		if err := rc.CalculateRackInformation(); err != nil {
+			return result.Error(err)
+		}
+
+		if res := rc.CheckRackCreation(); res.Completed() {
+			return res
+		}
+
+		waitingForRackScale := false
+		for _, sts := range rc.statefulSets {
+			currentReplicas := int(*sts.Spec.Replicas)
+			if currentReplicas > 0 {
+				waitingForRackScale = true
+				if err := rc.UpdateRackNodeCount(sts, 0); err != nil {
+					return result.Error(err)
+				}
+			}
+		}
+		if waitingForRackScale {
+			return result.RequeueSoon(5)
+		}
 	}
 
 	// Clean up annotation litter on the user Secrets
@@ -125,6 +150,14 @@ func (rc *ReconciliationContext) deletePVCs() error {
 		"numPVCs", len(persistentVolumeClaimList))
 
 	for _, pvc := range persistentVolumeClaimList {
+
+		if isBeingUsed, err := rc.isBeingUsed(pvc); err != nil {
+			logger.Error(err, "Failed to check if PVC is being used")
+			return err
+		} else if isBeingUsed {
+			return fmt.Errorf("PersistentVolumeClaim %s is still being used by a pod", pvc.Name)
+		}
+
 		if err := rc.Client.Delete(rc.Ctx, &pvc); err != nil {
 			logger.Error(err, "Failed to delete PVCs for cassandraDatacenter")
 			return err
@@ -138,6 +171,19 @@ func (rc *ReconciliationContext) deletePVCs() error {
 	return nil
 }
 
+func (rc *ReconciliationContext) isBeingUsed(pvc corev1.PersistentVolumeClaim) (bool, error) {
+	rc.ReqLogger.Info("reconciler::isBeingUsed")
+
+	pods := &corev1.PodList{}
+
+	if err := rc.Client.List(rc.Ctx, pods, &client.ListOptions{Namespace: pvc.Namespace, FieldSelector: fields.SelectorFromSet(fields.Set{"spec.volumes.persistentVolumeClaim.claimName": pvc.Name})}); err != nil {
+		rc.ReqLogger.Error(err, "error getting pods for pvc", "pvc", pvc.Name)
+		return false, err
+	}
+
+	return len(pods.Items) > 0, nil
+}
+
 func (rc *ReconciliationContext) listPVCs(selector map[string]string) ([]corev1.PersistentVolumeClaim, error) {
 	rc.ReqLogger.Info("reconciler::listPVCs")