Clarify error message when unsupported volume capabilities are provided

pkg/driver/controller.go

@@ -107,7 +107,10 @@ func (d *controllerService) CreateVolume(ctx context.Context, req *csi.CreateVol
 	}
 
 	if !isValidVolumeCapabilities(volCaps) {
-		return nil, status.Error(codes.InvalidArgument, "Volume capabilities not supported")
+		modes := util.GetAccessModes(volCaps)
+		stringModes := strings.Join(*modes, ", ")
+		errString := "Volume capabilities " + stringModes + " not supported. Only AccessModes[ReadWriteOnce] supported."
+		return nil, status.Error(codes.InvalidArgument, errString)
 	}
 
 	disk, err := d.cloud.GetDiskByName(ctx, volName, volSizeBytes)
@@ -256,7 +259,10 @@ func (d *controllerService) ControllerPublishVolume(ctx context.Context, req *cs
 
 	caps := []*csi.VolumeCapability{volCap}
 	if !isValidVolumeCapabilities(caps) {
-		return nil, status.Error(codes.InvalidArgument, "Volume capability not supported")
+		modes := util.GetAccessModes(caps)
+		stringModes := strings.Join(*modes, ", ")
+		errString := "Volume capabilities " + stringModes + " not supported. Only AccessModes[ReadWriteOnce] supported."
+		return nil, status.Error(codes.InvalidArgument, errString)
 	}
 
 	if !d.cloud.IsExistInstance(ctx, nodeID) {

pkg/util/util.go

@@ -23,6 +23,8 @@ import (
 	"path"
 	"path/filepath"
 	"strings"
+
+	csi "github.com/container-storage-interface/spec/lib/go/csi"
 )
 
 const (
@@ -78,3 +80,13 @@ func ParseEndpoint(endpoint string) (string, string, error) {
 func roundUpSize(volumeSizeBytes int64, allocationUnitBytes int64) int64 {
 	return (volumeSizeBytes + allocationUnitBytes - 1) / allocationUnitBytes
 }
+
+// GetAccessModes returns a slice containing all of the access modes defined
+// in the passed in VolumeCapabilities.
+func GetAccessModes(caps []*csi.VolumeCapability) *[]string {
+	modes := []string{}
+	for _, c := range caps {
+		modes = append(modes, c.AccessMode.GetMode().String())
+	}
+	return &modes
+}

pkg/util/util_test.go

@@ -18,7 +18,10 @@ package util
 
 import (
 	"fmt"
+	"reflect"
 	"testing"
+
+	csi "github.com/container-storage-interface/spec/lib/go/csi"
 )
 
 func TestRoundUpBytes(t *testing.T) {
@@ -125,3 +128,26 @@ func TestParseEndpoint(t *testing.T) {
 	}
 
 }
+
+func TestGetAccessModes(t *testing.T) {
+	testVolCap := []*csi.VolumeCapability{
+		{
+			AccessMode: &csi.VolumeCapability_AccessMode{
+				Mode: csi.VolumeCapability_AccessMode_SINGLE_NODE_WRITER,
+			},
+		},
+		{
+			AccessMode: &csi.VolumeCapability_AccessMode{
+				Mode: csi.VolumeCapability_AccessMode_SINGLE_NODE_READER_ONLY,
+			},
+		},
+	}
+	expectedModes := []string{
+		"SINGLE_NODE_WRITER",
+		"SINGLE_NODE_READER_ONLY",
+	}
+	actualModes := GetAccessModes(testVolCap)
+	if !reflect.DeepEqual(expectedModes, *actualModes) {
+		t.Fatalf("Wrong values returned for volume capabilities. Expected %v, got %v", expectedModes, actualModes)
+	}
+}