Implement CSI migration logic for volume resize

* Using PVC annotation for sychronication between in-tree resizer and extternal resizer
* Modify enqueue condition for resizer migration
* Add unit tests

pkg/controller/controller.go

@@ -123,11 +123,27 @@ func (ctrl *resizeController) updatePVC(oldObj, newObj interface{}) {
 	newSize := newPVC.Spec.Resources.Requests[v1.ResourceStorage]
 	oldSize := oldPVC.Spec.Resources.Requests[v1.ResourceStorage]
 
+	newResizerName := newPVC.Annotations[util.VolumeResizerKey]
+	oldResizerName := oldPVC.Annotations[util.VolumeResizerKey]
+
 	// We perform additional checks to avoid double processing of PVCs, as we will also receive Update event when:
 	// 1. Administrator or users may introduce other changes(such as add labels, modify annotations, etc.)
 	//    unrelated to volume resize.
 	// 2. Informer will resync and send Update event periodically without any changes.
-	if newSize.Cmp(oldSize) > 0 {
+	//
+	// We add the PVC into work queue when the new size is larger then the old size
+	// or when the resizer name changes. This is needed for CSI migration for the follow two cases:
+	//
+	// 1. First time a migrated PVC is expanded:
+	// It does not yet have the annotation because annotation is only added by in-tree resizer when it receives a volume
+	// expansion request. So first update event that will be received by external-resizer will be ignored because it won't
+	// know how to support resizing of a "un-annotated" in-tree PVC. When in-tree resizer does add the annotation, a second
+	// update even will be received and we add the pvc to workqueue. If annotation matches the registered driver name in
+	// csi_resizer object, we proceeds with expansion internally or we discard the PVC.
+	// 2. An already expanded in-tree PVC:
+	// An in-tree PVC is resized with in-tree resizer. And later, CSI migration is turned on and resizer name is updated from
+	// in-tree resizer name to CSI driver name.
+	if newSize.Cmp(oldSize) > 0 || newResizerName != oldResizerName {
 		ctrl.addPVC(newObj)
 	}
 }
@@ -249,7 +265,7 @@ func (ctrl *resizeController) pvcNeedResize(pvc *v1.PersistentVolumeClaim) bool
 
 // pvNeedResize returns true if a pv supports and also requests resize.
 func (ctrl *resizeController) pvNeedResize(pvc *v1.PersistentVolumeClaim, pv *v1.PersistentVolume) bool {
-	if !ctrl.resizer.CanSupport(pv) {
+	if !ctrl.resizer.CanSupport(pv, pvc) {
 		klog.V(4).Infof("Resizer %q doesn't support PV %q", ctrl.name, pv.Name)
 		return false
 	}

pkg/controller/controller_test.go

@@ -65,7 +65,7 @@ func TestController(t *testing.T) {
 			NodeResize:    true,
 		},
 	} {
-		client := csi.NewMockClient(test.NodeResize, true, true)
+		client := csi.NewMockClient("mock", test.NodeResize, true, true)
 		driverName, _ := client.GetDriverName(context.TODO())
 
 		initialObjects := []runtime.Object{}

pkg/csi/mock_client.go

@@ -3,11 +3,12 @@ package csi
 import "context"
 
 func NewMockClient(
+	name string,
 	supportsNodeResize bool,
 	supportsControllerResize bool,
 	supportsPluginControllerService bool) *MockClient {
 	return &MockClient{
-		name:                            "mock",
+		name:                            name,
 		supportsNodeResize:              supportsNodeResize,
 		supportsControllerResize:        supportsControllerResize,
 		supportsPluginControllerService: supportsPluginControllerService,

pkg/resizer/csi_resizer.go

@@ -23,12 +23,15 @@ import (
 	"time"
 
 	"github.com/kubernetes-csi/external-resizer/pkg/csi"
+	"github.com/kubernetes-csi/external-resizer/pkg/util"
 
 	"k8s.io/api/core/v1"
 	"k8s.io/apimachinery/pkg/api/resource"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/client-go/informers"
 	"k8s.io/client-go/kubernetes"
+
+	csitranslationlib "k8s.io/csi-translation-lib"
 	"k8s.io/klog"
 )
 
@@ -107,7 +110,18 @@ func (r *csiResizer) Name() string {
 	return r.name
 }
 
-func (r *csiResizer) CanSupport(pv *v1.PersistentVolume) bool {
+// CanSupport returns whether the PV is supported by resizer
+// Resizer will resize the volume if it is CSI volume or is migration enabled in-tree volume
+func (r *csiResizer) CanSupport(pv *v1.PersistentVolume, pvc *v1.PersistentVolumeClaim) bool {
+	resizerName := pvc.Annotations[util.VolumeResizerKey]
+	// resizerName will be CSI driver name when CSI migration is enabled
+	// otherwise, it will be in-tree plugin name
+	// r.name is the CSI driver name, return true only when they match
+	// and the CSI driver is migrated
+	if csitranslationlib.IsMigratedCSIDriverByName(r.name) && resizerName == r.name {
+		return true
+	}
+
 	source := pv.Spec.CSI
 	if source == nil {
 		klog.V(4).Infof("PV %s is not a CSI volume, skip it", pv.Name)
@@ -120,14 +134,32 @@ func (r *csiResizer) CanSupport(pv *v1.PersistentVolume) bool {
 	return true
 }
 
+// Resize resizes the persistence volume given request size
+// It supports both CSI volume and migrated in-tree volume
 func (r *csiResizer) Resize(pv *v1.PersistentVolume, requestSize resource.Quantity) (resource.Quantity, bool, error) {
 	oldSize := pv.Spec.Capacity[v1.ResourceStorage]
 
-	source := pv.Spec.CSI
-	if source == nil {
-		return oldSize, false, errors.New("not a CSI volume")
+	var volumeID string
+	var source *v1.CSIPersistentVolumeSource
+	if pv.Spec.CSI != nil {
+		// handle CSI volume
+		source = pv.Spec.CSI
+		volumeID = source.VolumeHandle
+	} else {
+		if csitranslationlib.IsMigratedCSIDriverByName(r.name) {
+			// handle migrated in-tree volume
+			csiPV, err := csitranslationlib.TranslateInTreePVToCSI(pv)
+			if err != nil {
+				return oldSize, false, fmt.Errorf("failed to translate persistent volume: %v", err)
+			}
+			source = csiPV.Spec.CSI
+			volumeID = source.VolumeHandle
+		} else {
+			// non-migrated in-tree volume
+			return oldSize, false, fmt.Errorf("volume %v is not migrated to CSI", pv.Name)
+		}
 	}
-	volumeID := source.VolumeHandle
+
 	if len(volumeID) == 0 {
 		return oldSize, false, errors.New("empty volume handle")
 	}
@@ -148,6 +180,7 @@ func (r *csiResizer) Resize(pv *v1.PersistentVolume, requestSize resource.Quanti
 	if err != nil {
 		return oldSize, nodeResizeRequired, err
 	}
+
 	return *resource.NewQuantity(newSizeBytes, resource.BinarySI), nodeResizeRequired, err
 }