Use storage class requested by statefulset instead of the old PVC

Until now we reused the storage class of the to be resized PVC. However
that can be an issue if the requested or default storage class changed
and the old storage class is not available anymore.

With this change we create new PVCs using the storage class (or the lack
of it, i.e. default) of the statefulset.

Author: glrf

controllers/controller_test.go

@@ -1,4 +1,5 @@
-//+build integration
+//go:build integration
+// +build integration
 
 package controllers
 
@@ -20,6 +21,7 @@ import (
 	rbacv1 "k8s.io/api/rbac/v1"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/runtime"
+	"k8s.io/utils/pointer"
 	ctrl "sigs.k8s.io/controller-runtime"
 	"sigs.k8s.io/controller-runtime/pkg/client"
 )
@@ -94,6 +96,7 @@ func TestController(t *testing.T) {
 			pvc := newSource(ns, "data-test-0", "1G",
 				func(pvc *corev1.PersistentVolumeClaim) *corev1.PersistentVolumeClaim {
 					pvc.Labels = sts.Spec.Selector.MatchLabels
+					pvc.Spec.StorageClassName = pointer.String("default-foobar") // Default storage class. Make sure it is not copied
 					return pvc
 				})
 			require.NoError(c.Create(ctx, pvc))

controllers/controller_util_test.go

@@ -1,4 +1,5 @@
-//+build integration
+//go:build integration
+// +build integration
 
 package controllers
 

controllers/pvc.go

@@ -40,7 +40,7 @@ func filterResizablePVCs(ctx context.Context, sts appsv1.StatefulSet, pvcs []cor
 		}
 		for _, tpl := range sts.Spec.VolumeClaimTemplates {
 			if isPVCTooSmall(ctx, p, tpl, sts.Name) {
-				res = append(res, pvc.NewEntity(p, tpl.Spec.Resources.Requests[corev1.ResourceStorage]))
+				res = append(res, pvc.NewEntity(p, tpl.Spec.Resources.Requests[corev1.ResourceStorage], tpl.Spec.StorageClassName))
 				break
 			}
 		}

go.mod

@@ -7,6 +7,7 @@ require (
 	k8s.io/api v0.21.3
 	k8s.io/apimachinery v0.21.3
 	k8s.io/client-go v0.21.3
+	k8s.io/utils v0.0.0-20210722164352-7f3ee0f31471
 	sigs.k8s.io/controller-runtime v0.9.5
 	sigs.k8s.io/controller-runtime/tools/setup-envtest v0.0.0-20210713022429-8b55f85c90c3
 	sigs.k8s.io/controller-tools v0.6.2

pvc/pvc.go

@@ -14,13 +14,15 @@ import (
 const ManagedLabel = "sts-resize.vshn.net/managed"
 
 // NewEntity returns a new pvc Info
-func NewEntity(pvc corev1.PersistentVolumeClaim, growTo resource.Quantity) Entity {
+func NewEntity(pvc corev1.PersistentVolumeClaim, growTo resource.Quantity, storageClassName *string) Entity {
+	pvc.Spec.StorageClassName = storageClassName
 	return Entity{
-		SourceName: pvc.Name,
-		Namespace:  pvc.Namespace,
-		Labels:     pvc.Labels,
-		TargetSize: growTo,
-		Spec:       pvc.Spec,
+		SourceName:         pvc.Name,
+		Namespace:          pvc.Namespace,
+		Labels:             pvc.Labels,
+		TargetSize:         growTo,
+		TargetStorageClass: storageClassName,
+		Spec:               pvc.Spec,
 	}
 }
 
@@ -29,9 +31,10 @@ type Entity struct {
 	Namespace  string
 	SourceName string
 
-	Labels     map[string]string
-	Spec       corev1.PersistentVolumeClaimSpec
-	TargetSize resource.Quantity
+	Labels             map[string]string
+	Spec               corev1.PersistentVolumeClaimSpec
+	TargetSize         resource.Quantity
+	TargetStorageClass *string
 
 	BackedUp bool
 	Restored bool
@@ -60,7 +63,7 @@ func (pi Entity) GetBackup() *corev1.PersistentVolumeClaim {
 		Spec: corev1.PersistentVolumeClaimSpec{
 			AccessModes:      pi.Spec.AccessModes,
 			Resources:        pi.Spec.Resources,
-			StorageClassName: pi.Spec.StorageClassName,
+			StorageClassName: pi.TargetStorageClass, // use target storage class. Old one might not be usable anymore
 			VolumeMode:       pi.Spec.VolumeMode,
 		},
 	}
@@ -81,7 +84,7 @@ func (pi Entity) GetResizedSource() *corev1.PersistentVolumeClaim {
 					corev1.ResourceStorage: pi.TargetSize,
 				},
 			},
-			StorageClassName: pi.Spec.StorageClassName,
+			StorageClassName: pi.TargetStorageClass,
 			VolumeMode:       pi.Spec.VolumeMode,
 		},
 	}

tools.go

@@ -1,3 +1,4 @@
+//go:build tools
 // +build tools
 
 package main