csi: Implement NodeServiceCapability_RPC_GET_VOLUME_STATS rpc call

and implement Metrics Provider for CSI driver

Signed-off-by: Humble Chirammal <hchiramm@redhat.com>

pkg/volume/csi/BUILD

@@ -7,6 +7,7 @@ go_library(
         "csi_block.go",
         "csi_client.go",
         "csi_drivers_store.go",
+        "csi_metrics.go",
         "csi_mounter.go",
         "csi_plugin.go",
         "csi_util.go",
@@ -50,6 +51,7 @@ go_test(
         "csi_block_test.go",
         "csi_client_test.go",
         "csi_drivers_store_test.go",
+        "csi_metrics_test.go",
         "csi_mounter_test.go",
         "csi_plugin_test.go",
         "expander_test.go",

pkg/volume/csi/csi_client.go

@@ -35,6 +35,7 @@ import (
 	utilfeature "k8s.io/apiserver/pkg/util/feature"
 	"k8s.io/klog"
 	"k8s.io/kubernetes/pkg/features"
+	"k8s.io/kubernetes/pkg/volume"
 	csipbv0 "k8s.io/kubernetes/pkg/volume/csi/csiv0"
 )
 
@@ -72,9 +73,16 @@ type csiClient interface {
 		secrets map[string]string,
 		volumeContext map[string]string,
 	) error
+
+	NodeGetVolumeStats(
+		ctx context.Context,
+		volID string,
+		targetPath string,
+	) (*volume.Metrics, error)
 	NodeUnstageVolume(ctx context.Context, volID, stagingTargetPath string) error
 	NodeSupportsStageUnstage(ctx context.Context) (bool, error)
 	NodeSupportsNodeExpand(ctx context.Context) (bool, error)
+	NodeSupportsVolumeStats(ctx context.Context) (bool, error)
 }
 
 // Strongly typed address
@@ -841,3 +849,101 @@ func (c *csiClientGetter) Get() (csiClient, error) {
 	c.csiClient = csi
 	return c.csiClient, nil
 }
+
+func (c *csiDriverClient) NodeSupportsVolumeStats(ctx context.Context) (bool, error) {
+	klog.V(5).Info(log("calling NodeGetCapabilities rpc to determine if NodeSupportsVolumeStats"))
+	if c.nodeV1ClientCreator != nil {
+		return c.nodeSupportsVolumeStatsV1(ctx)
+	}
+	return false, fmt.Errorf("failed to call NodeSupportsVolumeStats. nodeV1ClientCreator is nil")
+}
+
+func (c *csiDriverClient) nodeSupportsVolumeStatsV1(ctx context.Context) (bool, error) {
+	nodeClient, closer, err := c.nodeV1ClientCreator(c.addr)
+	if err != nil {
+		return false, err
+	}
+	defer closer.Close()
+	req := &csipbv1.NodeGetCapabilitiesRequest{}
+	resp, err := nodeClient.NodeGetCapabilities(ctx, req)
+	if err != nil {
+		return false, err
+	}
+	capabilities := resp.GetCapabilities()
+	if capabilities == nil {
+		return false, nil
+	}
+	for _, capability := range capabilities {
+		if capability.GetRpc().GetType() == csipbv1.NodeServiceCapability_RPC_GET_VOLUME_STATS {
+			return true, nil
+		}
+	}
+	return false, nil
+}
+
+func (c *csiDriverClient) NodeGetVolumeStats(ctx context.Context, volID string, targetPath string) (*volume.Metrics, error) {
+	klog.V(4).Info(log("calling NodeGetVolumeStats rpc: [volid=%s, target_path=%s", volID, targetPath))
+	if volID == "" {
+		return nil, errors.New("missing volume id")
+	}
+	if targetPath == "" {
+		return nil, errors.New("missing target path")
+	}
+
+	if c.nodeV1ClientCreator != nil {
+		return c.nodeGetVolumeStatsV1(ctx, volID, targetPath)
+	}
+
+	return nil, fmt.Errorf("failed to call NodeGetVolumeStats. nodeV1ClientCreator is nil")
+}
+
+func (c *csiDriverClient) nodeGetVolumeStatsV1(
+	ctx context.Context,
+	volID string,
+	targetPath string,
+) (*volume.Metrics, error) {
+	nodeClient, closer, err := c.nodeV1ClientCreator(c.addr)
+	if err != nil {
+		return nil, err
+	}
+	defer closer.Close()
+
+	req := &csipbv1.NodeGetVolumeStatsRequest{
+		VolumeId:   volID,
+		VolumePath: targetPath,
+	}
+
+	resp, err := nodeClient.NodeGetVolumeStats(ctx, req)
+	if err != nil {
+		return nil, err
+	}
+	usages := resp.GetUsage()
+	if usages == nil {
+		return nil, fmt.Errorf("failed to get usage from response. usage is nil")
+	}
+	metrics := &volume.Metrics{
+		Used:       resource.NewQuantity(int64(0), resource.BinarySI),
+		Capacity:   resource.NewQuantity(int64(0), resource.BinarySI),
+		Available:  resource.NewQuantity(int64(0), resource.BinarySI),
+		InodesUsed: resource.NewQuantity(int64(0), resource.BinarySI),
+		Inodes:     resource.NewQuantity(int64(0), resource.BinarySI),
+		InodesFree: resource.NewQuantity(int64(0), resource.BinarySI),
+	}
+	for _, usage := range usages {
+		unit := usage.GetUnit()
+		switch unit {
+		case csipbv1.VolumeUsage_BYTES:
+			metrics.Available = resource.NewQuantity(usage.GetAvailable(), resource.BinarySI)
+			metrics.Capacity = resource.NewQuantity(usage.GetTotal(), resource.BinarySI)
+			metrics.Used = resource.NewQuantity(usage.GetUsed(), resource.BinarySI)
+		case csipbv1.VolumeUsage_INODES:
+			metrics.InodesFree = resource.NewQuantity(usage.GetAvailable(), resource.BinarySI)
+			metrics.Inodes = resource.NewQuantity(usage.GetTotal(), resource.BinarySI)
+			metrics.InodesUsed = resource.NewQuantity(usage.GetUsed(), resource.BinarySI)
+		default:
+			klog.Errorf("unknown key %s in usage", unit.String())
+		}
+
+	}
+	return metrics, nil
+}

pkg/volume/csi/csi_client_test.go

@@ -26,6 +26,7 @@ import (
 	csipbv1 "github.com/container-storage-interface/spec/lib/go/csi"
 	api "k8s.io/api/core/v1"
 	"k8s.io/apimachinery/pkg/api/resource"
+	"k8s.io/kubernetes/pkg/volume"
 	"k8s.io/kubernetes/pkg/volume/csi/fake"
 )
 
@@ -48,6 +49,13 @@ func newFakeCsiDriverClientWithExpansion(t *testing.T, stagingCapable bool, expa
 	}
 }
 
+func newFakeCsiDriverClientWithVolumeStats(t *testing.T, volumeStatsSet bool) *fakeCsiDriverClient {
+	return &fakeCsiDriverClient{
+		t:          t,
+		nodeClient: fake.NewNodeClientWithVolumeStats(volumeStatsSet),
+	}
+}
+
 func (c *fakeCsiDriverClient) NodeGetInfo(ctx context.Context) (
 	nodeID string,
 	maxVolumePerNode int64,
@@ -61,6 +69,54 @@ func (c *fakeCsiDriverClient) NodeGetInfo(ctx context.Context) (
 	return resp.GetNodeId(), resp.GetMaxVolumesPerNode(), accessibleTopology, err
 }
 
+func (c *fakeCsiDriverClient) NodeGetVolumeStats(ctx context.Context, volID string, targetPath string) (
+	usageCountMap *volume.Metrics, err error) {
+	c.t.Log("calling fake.NodeGetVolumeStats...")
+	req := &csipbv1.NodeGetVolumeStatsRequest{
+		VolumeId:   volID,
+		VolumePath: targetPath,
+	}
+	resp, err := c.nodeClient.NodeGetVolumeStats(ctx, req)
+	usages := resp.GetUsage()
+	metrics := &volume.Metrics{}
+	if usages == nil {
+		return nil, nil
+	}
+	for _, usage := range usages {
+		unit := usage.GetUnit()
+		switch unit {
+		case csipbv1.VolumeUsage_BYTES:
+			metrics.Available = resource.NewQuantity(usage.GetAvailable(), resource.BinarySI)
+			metrics.Capacity = resource.NewQuantity(usage.GetTotal(), resource.BinarySI)
+			metrics.Used = resource.NewQuantity(usage.GetUsed(), resource.BinarySI)
+		case csipbv1.VolumeUsage_INODES:
+			metrics.InodesFree = resource.NewQuantity(usage.GetAvailable(), resource.BinarySI)
+			metrics.Inodes = resource.NewQuantity(usage.GetTotal(), resource.BinarySI)
+			metrics.InodesUsed = resource.NewQuantity(usage.GetUsed(), resource.BinarySI)
+		}
+	}
+	return metrics, nil
+}
+
+func (c *fakeCsiDriverClient) NodeSupportsVolumeStats(ctx context.Context) (bool, error) {
+	c.t.Log("calling fake.NodeSupportsVolumeStats...")
+	req := &csipbv1.NodeGetCapabilitiesRequest{}
+	resp, err := c.nodeClient.NodeGetCapabilities(ctx, req)
+	if err != nil {
+		return false, err
+	}
+	capabilities := resp.GetCapabilities()
+	if capabilities == nil {
+		return false, nil
+	}
+	for _, capability := range capabilities {
+		if capability.GetRpc().GetType() == csipbv1.NodeServiceCapability_RPC_GET_VOLUME_STATS {
+			return true, nil
+		}
+	}
+	return false, nil
+}
+
 func (c *fakeCsiDriverClient) NodePublishVolume(
 	ctx context.Context,
 	volID string,
@@ -220,6 +276,10 @@ func setupClientWithExpansion(t *testing.T, stageUnstageSet bool, expansionSet b
 	return newFakeCsiDriverClientWithExpansion(t, stageUnstageSet, expansionSet)
 }
 
+func setupClientWithVolumeStats(t *testing.T, volumeStatsSet bool) csiClient {
+	return newFakeCsiDriverClientWithVolumeStats(t, volumeStatsSet)
+}
+
 func checkErr(t *testing.T, expectedAnError bool, actualError error) {
 	t.Helper()
 
@@ -521,3 +581,90 @@ func TestNodeExpandVolume(t *testing.T) {
 		}
 	}
 }
+
+type VolumeStatsOptions struct {
+	VolumeSpec *volume.Spec
+
+	// this just could be volumeID
+	VolumeID string
+
+	// DeviceMountPath location where device is mounted on the node. If volume type
+	// is attachable - this would be global mount path otherwise
+	// it would be location where volume was mounted for the pod
+	DeviceMountPath string
+}
+
+func TestVolumeStats(t *testing.T) {
+	spec := volume.NewSpecFromPersistentVolume(makeTestPV("test-pv", 10, "metrics", "test-vol"), false)
+	tests := []struct {
+		name           string
+		volumeStatsSet bool
+		volumeData     VolumeStatsOptions
+		success        bool
+	}{
+		{
+			name:           "when nodeVolumeStats=on, VolumeID=on, DeviceMountPath=on",
+			volumeStatsSet: true,
+			volumeData: VolumeStatsOptions{
+				VolumeSpec:      spec,
+				VolumeID:        "volume1",
+				DeviceMountPath: "/foo/bar",
+			},
+			success: true,
+		},
+
+		{
+			name:           "when nodeVolumeStats=off, VolumeID=on, DeviceMountPath=on",
+			volumeStatsSet: false,
+			volumeData: VolumeStatsOptions{
+				VolumeSpec:      spec,
+				VolumeID:        "volume1",
+				DeviceMountPath: "/foo/bar",
+			},
+			success: false,
+		},
+
+		{
+			name:           "when nodeVolumeStats=on, VolumeID=off, DeviceMountPath=on",
+			volumeStatsSet: true,
+			volumeData: VolumeStatsOptions{
+				VolumeSpec:      spec,
+				VolumeID:        "",
+				DeviceMountPath: "/foo/bar",
+			},
+			success: false,
+		},
+
+		{
+			name:           "when nodeVolumeStats=on, VolumeID=on, DeviceMountPath=off",
+			volumeStatsSet: true,
+			volumeData: VolumeStatsOptions{
+				VolumeSpec:      spec,
+				VolumeID:        "volume1",
+				DeviceMountPath: "",
+			},
+			success: false,
+		},
+		{
+			name:           "when nodeVolumeStats=on, VolumeID=on, DeviceMountPath=off",
+			volumeStatsSet: true,
+			volumeData: VolumeStatsOptions{
+				VolumeSpec:      spec,
+				VolumeID:        "",
+				DeviceMountPath: "",
+			},
+			success: false,
+		},
+	}
+	for _, tc := range tests {
+		ctx, cancel := context.WithTimeout(context.Background(), csiTimeout)
+		defer cancel()
+		csiSource, _ := getCSISourceFromSpec(tc.volumeData.VolumeSpec)
+		csClient := setupClientWithVolumeStats(t, tc.volumeStatsSet)
+		_, err := csClient.NodeGetVolumeStats(ctx, csiSource.VolumeHandle, tc.volumeData.DeviceMountPath)
+		if err != nil && tc.success {
+			t.Errorf("For %s : expected %v got %v", tc.name, tc.success, err)
+		}
+	}
+
+}

pkg/volume/csi/csi_metrics.go

@@ -0,0 +1,79 @@
+/*
+Copyright 2019 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package csi
+
+import (
+	"context"
+	"fmt"
+
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/kubernetes/pkg/volume"
+)
+
+var _ volume.MetricsProvider = &metricsCsi{}
+
+// metricsCsi represents a MetricsProvider that calculates the used,free and
+// capacity information for volume using volume path.
+
+type metricsCsi struct {
+	// the directory path the volume is mounted to.
+	targetPath string
+
+	// Volume handle or id
+	volumeID string
+
+	//csiClient with cache
+	csiClientGetter
+}
+
+// NewMetricsCsi creates a new metricsCsi with the Volume ID and path.
+func NewMetricsCsi(volumeID string, targetPath string, driverName csiDriverName) volume.MetricsProvider {
+	mc := &metricsCsi{volumeID: volumeID, targetPath: targetPath}
+	mc.csiClientGetter.driverName = driverName
+	return mc
+}
+
+func (mc *metricsCsi) GetMetrics() (*volume.Metrics, error) {
+	currentTime := metav1.Now()
+	ctx, cancel := context.WithTimeout(context.Background(), csiTimeout)
+	defer cancel()
+	// Get CSI client
+	csiClient, err := mc.csiClientGetter.Get()
+	if err != nil {
+		return nil, err
+	}
+	// Check whether "GET_VOLUME_STATS" is set
+	volumeStatsSet, err := csiClient.NodeSupportsVolumeStats(ctx)
+	if err != nil {
+		return nil, err
+	}
+	// if plugin doesnot support volume status, return.
+	if !volumeStatsSet {
+		return nil, nil
+	}
+	// Get Volumestatus
+	metrics, err := csiClient.NodeGetVolumeStats(ctx, mc.volumeID, mc.targetPath)
+	if err != nil {
+		return nil, err
+	}
+	if metrics == nil {
+		return nil, fmt.Errorf("csi.NodeGetVolumeStats returned nil metrics for volume %s", mc.volumeID)
+	}
+	//set recorded time
+	metrics.Time = currentTime
+	return metrics, nil
+}

pkg/volume/csi/csi_metrics_test.go

@@ -0,0 +1,113 @@
+/*
+Copyright 2019 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package csi
+
+import (
+	"io"
+	"testing"
+
+	csipbv1 "github.com/container-storage-interface/spec/lib/go/csi"
+	"k8s.io/apimachinery/pkg/api/resource"
+	"k8s.io/kubernetes/pkg/volume/csi/fake"
+)
+
+func TestGetMetrics(t *testing.T) {
+	tests := []struct {
+		name          string
+		volumeID      string
+		targetPath    string
+		expectSuccess bool
+	}{
+		{
+			name:          "with valid name and volume id",
+			expectSuccess: true,
+			volumeID:      "foobar",
+			targetPath:    "/mnt/foo",
+		},
+	}
+
+	for _, tc := range tests {
+		metricsGetter := &metricsCsi{volumeID: tc.volumeID, targetPath: tc.targetPath}
+		metricsGetter.csiClient = &csiDriverClient{
+			driverName: "com.google.gcepd",
+			nodeV1ClientCreator: func(addr csiAddr) (csipbv1.NodeClient, io.Closer, error) {
+				nodeClient := fake.NewNodeClientWithVolumeStats(true /* VolumeStatsCapable */)
+				fakeCloser := fake.NewCloser(t)
+				nodeClient.SetNodeVolumeStatsResp(getRawVolumeInfo())
+				return nodeClient, fakeCloser, nil
+			},
+		}
+		metrics, err := metricsGetter.GetMetrics()
+		if err != nil {
+			t.Fatalf("for %s: unexpected error : %v", tc.name, err)
+		}
+		if metrics == nil {
+			t.Fatalf("unexpected nil metrics")
+		}
+		expectedMetrics := getRawVolumeInfo()
+		for _, usage := range expectedMetrics.Usage {
+			if usage.Unit == csipbv1.VolumeUsage_BYTES {
+				availableBytes := resource.NewQuantity(usage.Available, resource.BinarySI)
+				totalBytes := resource.NewQuantity(usage.Total, resource.BinarySI)
+				usedBytes := resource.NewQuantity(usage.Used, resource.BinarySI)
+				if metrics.Available.Cmp(*availableBytes) != 0 {
+					t.Fatalf("for %s: error: expected :%v , got: %v", tc.name, *availableBytes, *(metrics.Available))
+				}
+				if metrics.Capacity.Cmp(*totalBytes) != 0 {
+					t.Fatalf("for %s: error: expected :%v , got: %v", tc.name, *totalBytes, *(metrics.Capacity))
+				}
+				if metrics.Used.Cmp(*usedBytes) != 0 {
+					t.Fatalf("for %s: error: expected :%v , got: %v", tc.name, *usedBytes, *(metrics.Used))
+				}
+			}
+
+			if usage.Unit == csipbv1.VolumeUsage_INODES {
+				freeInodes := resource.NewQuantity(usage.Available, resource.BinarySI)
+				inodes := resource.NewQuantity(usage.Total, resource.BinarySI)
+				usedInodes := resource.NewQuantity(usage.Used, resource.BinarySI)
+				if metrics.InodesFree.Cmp(*freeInodes) != 0 {
+					t.Fatalf("for %s: error: expected :%v , got: %v", tc.name, *freeInodes, *(metrics.InodesFree))
+				}
+				if metrics.Inodes.Cmp(*inodes) != 0 {
+					t.Fatalf("for %s: error: expected :%v , got: %v", tc.name, *inodes, *(metrics.Inodes))
+				}
+				if metrics.InodesUsed.Cmp(*usedInodes) != 0 {
+					t.Fatalf("for %s: error: expected :%v , got: %v", tc.name, *usedInodes, *(metrics.InodesUsed))
+				}
+			}
+		}
+	}
+}
+
+func getRawVolumeInfo() *csipbv1.NodeGetVolumeStatsResponse {
+	return &csipbv1.NodeGetVolumeStatsResponse{
+		Usage: []*csipbv1.VolumeUsage{
+			{
+				Available: int64(10),
+				Total:     int64(10),
+				Used:      int64(2),
+				Unit:      csipbv1.VolumeUsage_BYTES,
+			},
+			{
+				Available: int64(100),
+				Total:     int64(100),
+				Used:      int64(20),
+				Unit:      csipbv1.VolumeUsage_INODES,
+			},
+		},
+	}
+}

pkg/volume/csi/csi_mounter.go

@@ -69,7 +69,7 @@ type csiMountMgr struct {
 	podUID         types.UID
 	options        volume.VolumeOptions
 	publishContext map[string]string
-	volume.MetricsNil
+	volume.MetricsProvider
 }
 
 // volume.Volume methods

pkg/volume/csi/csi_plugin.go

@@ -408,6 +408,8 @@ func (p *csiPlugin) NewMounter(
 	}
 	klog.V(4).Info(log("created path successfully [%s]", dataDir))
 
+	mounter.MetricsProvider = NewMetricsCsi(volumeHandle, dir, csiDriverName(driverName))
+
 	// persist volume info data for teardown
 	node := string(p.host.GetNodeName())
 	volData := map[string]string{

pkg/volume/csi/fake/fake_client.go

@@ -71,7 +71,9 @@ type NodeClient struct {
 	nodeStagedVolumes    map[string]CSIVolume
 	stageUnstageSet      bool
 	expansionSet         bool
+	volumeStatsSet       bool
 	nodeGetInfoResp      *csipb.NodeGetInfoResponse
+	nodeVolumeStatsResp  *csipb.NodeGetVolumeStatsResponse
 	nextErr              error
 }
 
@@ -81,6 +83,7 @@ func NewNodeClient(stageUnstageSet bool) *NodeClient {
 		nodePublishedVolumes: make(map[string]CSIVolume),
 		nodeStagedVolumes:    make(map[string]CSIVolume),
 		stageUnstageSet:      stageUnstageSet,
+		volumeStatsSet:       true,
 	}
 }
 
@@ -93,6 +96,12 @@ func NewNodeClientWithExpansion(stageUnstageSet bool, expansionSet bool) *NodeCl
 	}
 }
 
+func NewNodeClientWithVolumeStats(volumeStatsSet bool) *NodeClient {
+	return &NodeClient{
+		volumeStatsSet: volumeStatsSet,
+	}
+}
+
 // SetNextError injects next expected error
 func (f *NodeClient) SetNextError(err error) {
 	f.nextErr = err
@@ -102,6 +111,10 @@ func (f *NodeClient) SetNodeGetInfoResp(resp *csipb.NodeGetInfoResponse) {
 	f.nodeGetInfoResp = resp
 }
 
+func (f *NodeClient) SetNodeVolumeStatsResp(resp *csipb.NodeGetVolumeStatsResponse) {
+	f.nodeVolumeStatsResp = resp
+}
+
 // GetNodePublishedVolumes returns node published volumes
 func (f *NodeClient) GetNodePublishedVolumes() map[string]CSIVolume {
 	return f.nodePublishedVolumes
@@ -264,13 +277,42 @@ func (f *NodeClient) NodeGetCapabilities(ctx context.Context, in *csipb.NodeGetC
 			},
 		})
 	}
+
+	if f.volumeStatsSet {
+		resp.Capabilities = append(resp.Capabilities, &csipb.NodeServiceCapability{
+			Type: &csipb.NodeServiceCapability_Rpc{
+				Rpc: &csipb.NodeServiceCapability_RPC{
+					Type: csipb.NodeServiceCapability_RPC_GET_VOLUME_STATS,
+				},
+			},
+		})
+	}
 	return resp, nil
 }
 
+/*
 // NodeGetVolumeStats implements csi method
 func (f *NodeClient) NodeGetVolumeStats(ctx context.Context, in *csipb.NodeGetVolumeStatsRequest, opts ...grpc.CallOption) (*csipb.NodeGetVolumeStatsResponse, error) {
 	return nil, nil
 }
+*/
+
+// NodeGetVolumeStats implements csi method
+func (f *NodeClient) NodeGetVolumeStats(ctx context.Context, req *csipb.NodeGetVolumeStatsRequest, opts ...grpc.CallOption) (*csipb.NodeGetVolumeStatsResponse, error) {
+	if f.nextErr != nil {
+		return nil, f.nextErr
+	}
+	if req.GetVolumeId() == "" {
+		return nil, errors.New("missing volume id")
+	}
+	if req.GetVolumePath() == "" {
+		return nil, errors.New("missing Volume path")
+	}
+	if f.nodeVolumeStatsResp != nil {
+		return f.nodeVolumeStatsResp, nil
+	}
+	return &csipb.NodeGetVolumeStatsResponse{}, nil
+}
 
 // ControllerClient represents a CSI Controller client
 type ControllerClient struct {