/*
Copyright 2015 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 glusterfs

import (
	"context"
	"crypto/tls"
	"fmt"
	"math"
	"math/rand"
	"net"
	"net/http"
	"os"
	"path/filepath"
	"runtime"
	"strconv"
	dstrings "strings"
	"sync"

	gcli "github.com/heketi/heketi/client/api/go-client"
	gapi "github.com/heketi/heketi/pkg/glusterfs/api"
	"k8s.io/klog/v2"
	"k8s.io/mount-utils"
	utilstrings "k8s.io/utils/strings"

	v1 "k8s.io/api/core/v1"
	"k8s.io/apimachinery/pkg/api/errors"
	"k8s.io/apimachinery/pkg/api/resource"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/apimachinery/pkg/labels"
	"k8s.io/apimachinery/pkg/types"
	"k8s.io/apimachinery/pkg/util/sets"
	"k8s.io/apimachinery/pkg/util/uuid"
	clientset "k8s.io/client-go/kubernetes"
	volumehelpers "k8s.io/cloud-provider/volume/helpers"
	storagehelpers "k8s.io/component-helpers/storage/volume"
	proxyutil "k8s.io/kubernetes/pkg/proxy/util"
	"k8s.io/kubernetes/pkg/volume"
	volutil "k8s.io/kubernetes/pkg/volume/util"
)

// ProbeVolumePlugins is the primary entrypoint for volume plugins.
func ProbeVolumePlugins() []volume.VolumePlugin {
	return []volume.VolumePlugin{&glusterfsPlugin{host: nil, gidTable: make(map[string]*MinMaxAllocator)}}
}

type glusterfsPlugin struct {
	host         volume.VolumeHost
	gidTable     map[string]*MinMaxAllocator
	gidTableLock sync.Mutex
}

var _ volume.VolumePlugin = &glusterfsPlugin{}
var _ volume.PersistentVolumePlugin = &glusterfsPlugin{}
var _ volume.DeletableVolumePlugin = &glusterfsPlugin{}
var _ volume.ProvisionableVolumePlugin = &glusterfsPlugin{}
var _ volume.ExpandableVolumePlugin = &glusterfsPlugin{}
var _ volume.Provisioner = &glusterfsVolumeProvisioner{}
var _ volume.Deleter = &glusterfsVolumeDeleter{}

const (
	glusterfsPluginName            = "kubernetes.io/glusterfs"
	volPrefix                      = "vol_"
	dynamicEpSvcPrefix             = "glusterfs-dynamic"
	replicaCount                   = 3
	secretKeyName                  = "key" // key name used in secret
	gciLinuxGlusterMountBinaryPath = "/sbin/mount.glusterfs"
	defaultGidMin                  = 2000
	defaultGidMax                  = math.MaxInt32

	// maxCustomEpNamePrefix is the maximum number of chars.
	// which can be used as ep/svc name prefix. This number is carved
	// out from below formula.
	// max length of name of an ep - length of pvc uuid
	// where max length of name of an ep is 63 and length of uuid is 37
	maxCustomEpNamePrefixLen = 26

	// absoluteGidMin/Max are currently the same as the
	// default values, but they play a different role and
	// could take a different value. Only thing we need is:
	// absGidMin <= defGidMin <= defGidMax <= absGidMax
	absoluteGidMin = 2000
	absoluteGidMax = math.MaxInt32
	heketiAnn      = "heketi-dynamic-provisioner"
	glusterTypeAnn = "gluster.org/type"
	glusterDescAnn = "Gluster-Internal: Dynamically provisioned PV"
	heketiVolIDAnn = "gluster.kubernetes.io/heketi-volume-id"

	// Error string returned by heketi
	errIDNotFound = "Id not found"
)

func (plugin *glusterfsPlugin) Init(host volume.VolumeHost) error {
	plugin.host = host
	return nil
}

func (plugin *glusterfsPlugin) GetPluginName() string {
	return glusterfsPluginName
}

func (plugin *glusterfsPlugin) GetVolumeName(spec *volume.Spec) (string, error) {
	return "", fmt.Errorf("GetVolumeName() is unimplemented for GlusterFS")
}

func (plugin *glusterfsPlugin) CanSupport(spec *volume.Spec) bool {
	return (spec.PersistentVolume != nil && spec.PersistentVolume.Spec.Glusterfs != nil) ||
		(spec.Volume != nil && spec.Volume.Glusterfs != nil)
}

func (plugin *glusterfsPlugin) RequiresRemount(spec *volume.Spec) bool {
	return false
}

func (plugin *glusterfsPlugin) SupportsMountOption() bool {
	return true
}

func (plugin *glusterfsPlugin) SupportsBulkVolumeVerification() bool {
	return false
}

func (plugin *glusterfsPlugin) RequiresFSResize() bool {
	return false
}

func (plugin *glusterfsPlugin) GetAccessModes() []v1.PersistentVolumeAccessMode {
	return []v1.PersistentVolumeAccessMode{
		v1.ReadWriteOnce,
		v1.ReadOnlyMany,
		v1.ReadWriteMany,
	}
}

func (plugin *glusterfsPlugin) NewMounter(spec *volume.Spec, pod *v1.Pod, _ volume.VolumeOptions) (volume.Mounter, error) {
	epName, epNamespace, err := plugin.getEndpointNameAndNamespace(spec, pod.Namespace)
	if err != nil {
		return nil, err
	}
	kubeClient := plugin.host.GetKubeClient()
	if kubeClient == nil {
		return nil, fmt.Errorf("failed to get kube client to initialize mounter")
	}
	ep, err := kubeClient.CoreV1().Endpoints(epNamespace).Get(context.TODO(), epName, metav1.GetOptions{})
	if err != nil {
		klog.Errorf("failed to get endpoint %s: %v", epName, err)
		return nil, err
	}
	klog.V(4).Infof("glusterfs pv endpoint %v", ep)
	return plugin.newMounterInternal(spec, ep, pod, plugin.host.GetMounter(plugin.GetPluginName()))
}

func (plugin *glusterfsPlugin) getEndpointNameAndNamespace(spec *volume.Spec, defaultNamespace string) (string, string, error) {
	if spec.Volume != nil && spec.Volume.Glusterfs != nil {
		endpoints := spec.Volume.Glusterfs.EndpointsName
		if endpoints == "" {
			return "", "", fmt.Errorf("no glusterFS endpoint specified")
		}
		return endpoints, defaultNamespace, nil
	} else if spec.PersistentVolume != nil &&
		spec.PersistentVolume.Spec.Glusterfs != nil {
		endpoints := spec.PersistentVolume.Spec.Glusterfs.EndpointsName
		endpointsNs := defaultNamespace
		overriddenNs := spec.PersistentVolume.Spec.Glusterfs.EndpointsNamespace
		if overriddenNs != nil {
			if len(*overriddenNs) > 0 {
				endpointsNs = *overriddenNs
			} else {
				return "", "", fmt.Errorf("endpointnamespace field set, but no endpointnamespace specified")
			}
		}
		return endpoints, endpointsNs, nil
	}
	return "", "", fmt.Errorf("spec does not reference a GlusterFS volume type")

}
func (plugin *glusterfsPlugin) newMounterInternal(spec *volume.Spec, ep *v1.Endpoints, pod *v1.Pod, mounter mount.Interface) (volume.Mounter, error) {
	volPath, readOnly, err := getVolumeInfo(spec)
	if err != nil {
		klog.Errorf("failed to get volumesource: %v", err)
		return nil, err
	}
	return &glusterfsMounter{
		glusterfs: &glusterfs{
			volName:         spec.Name(),
			mounter:         mounter,
			pod:             pod,
			plugin:          plugin,
			MetricsProvider: volume.NewMetricsStatFS(plugin.host.GetPodVolumeDir(pod.UID, utilstrings.EscapeQualifiedName(glusterfsPluginName), spec.Name())),
		},
		hosts:        ep,
		path:         volPath,
		readOnly:     readOnly,
		mountOptions: volutil.MountOptionFromSpec(spec),
	}, nil
}

func (plugin *glusterfsPlugin) NewUnmounter(volName string, podUID types.UID) (volume.Unmounter, error) {
	return plugin.newUnmounterInternal(volName, podUID, plugin.host.GetMounter(plugin.GetPluginName()))
}

func (plugin *glusterfsPlugin) newUnmounterInternal(volName string, podUID types.UID, mounter mount.Interface) (volume.Unmounter, error) {
	return &glusterfsUnmounter{&glusterfs{
		volName:         volName,
		mounter:         mounter,
		pod:             &v1.Pod{ObjectMeta: metav1.ObjectMeta{UID: podUID}},
		plugin:          plugin,
		MetricsProvider: volume.NewMetricsStatFS(plugin.host.GetPodVolumeDir(podUID, utilstrings.EscapeQualifiedName(glusterfsPluginName), volName)),
	}}, nil
}

func (plugin *glusterfsPlugin) ConstructVolumeSpec(volumeName, mountPath string) (*volume.Spec, error) {

	// To reconstruct volume spec we need endpoint where fetching endpoint from mount
	// string looks to be impossible, so returning error.
	return nil, fmt.Errorf("impossible to reconstruct glusterfs volume spec from volume mountpath")
}

// Glusterfs volumes represent a bare host file or directory mount of an Glusterfs export.
type glusterfs struct {
	volName string
	pod     *v1.Pod
	mounter mount.Interface
	plugin  *glusterfsPlugin
	volume.MetricsProvider
}

type glusterfsMounter struct {
	*glusterfs
	hosts        *v1.Endpoints
	path         string
	readOnly     bool
	mountOptions []string
}

var _ volume.Mounter = &glusterfsMounter{}

func (b *glusterfsMounter) GetAttributes() volume.Attributes {
	return volume.Attributes{
		ReadOnly:        b.readOnly,
		Managed:         false,
		SupportsSELinux: false,
	}
}

// Checks prior to mount operations to verify that the required components (binaries, etc.)
// to mount the volume are available on the underlying node.
// If not, it returns an error
func (b *glusterfsMounter) CanMount() error {
	exe := b.plugin.host.GetExec(b.plugin.GetPluginName())
	switch runtime.GOOS {
	case "linux":
		if _, err := exe.Command("test", "-x", gciLinuxGlusterMountBinaryPath).CombinedOutput(); err != nil {
			return fmt.Errorf("required binary %s is missing", gciLinuxGlusterMountBinaryPath)
		}
	}
	return nil
}

// SetUp attaches the disk and bind mounts to the volume path.
func (b *glusterfsMounter) SetUp(mounterArgs volume.MounterArgs) error {
	return b.SetUpAt(b.GetPath(), mounterArgs)
}

func (b *glusterfsMounter) SetUpAt(dir string, mounterArgs volume.MounterArgs) error {
	notMnt, err := b.mounter.IsLikelyNotMountPoint(dir)
	klog.V(4).Infof("mount setup: %s %v %v", dir, !notMnt, err)
	if err != nil && !os.IsNotExist(err) {
		return err
	}
	if !notMnt {
		return nil
	}
	if err := os.MkdirAll(dir, 0750); err != nil {
		return err
	}
	err = b.setUpAtInternal(dir)
	if err == nil {
		return nil
	}

	// Cleanup upon failure.
	mount.CleanupMountPoint(dir, b.mounter, false)
	return err
}

func (glusterfsVolume *glusterfs) GetPath() string {
	name := glusterfsPluginName
	return glusterfsVolume.plugin.host.GetPodVolumeDir(glusterfsVolume.pod.UID, utilstrings.EscapeQualifiedName(name), glusterfsVolume.volName)
}

type glusterfsUnmounter struct {
	*glusterfs
}

var _ volume.Unmounter = &glusterfsUnmounter{}

func (c *glusterfsUnmounter) TearDown() error {
	return c.TearDownAt(c.GetPath())
}

func (c *glusterfsUnmounter) TearDownAt(dir string) error {
	return mount.CleanupMountPoint(dir, c.mounter, false)
}

func (b *glusterfsMounter) setUpAtInternal(dir string) error {
	var errs error
	options := []string{}
	hasLogFile := false
	hasLogLevel := false
	log := ""
	if b.readOnly {
		options = append(options, "ro")
	}

	// Check for log-file,log-level options existence in user supplied mount options, if provided, use those.
	for _, userOpt := range b.mountOptions {
		switch {
		case dstrings.HasPrefix(userOpt, "log-file"):
			klog.V(4).Infof("log-file mount option has provided")
			hasLogFile = true

		case dstrings.HasPrefix(userOpt, "log-level"):
			klog.V(4).Infof("log-level mount option has provided")
			hasLogLevel = true
		}
	}

	// If logfile has not been provided, create driver specific log file.
	if !hasLogFile {
		p := filepath.Join(b.glusterfs.plugin.host.GetPluginDir(glusterfsPluginName), b.glusterfs.volName)
		if err := os.MkdirAll(p, 0750); err != nil {
			return fmt.Errorf("failed to create directory %v: %v", p, err)
		}

		// adding log-level ERROR to remove noise
		// and more specific log path so each pod has
		// its own log based on PV + Pod
		log = filepath.Join(p, b.pod.Name+"-glusterfs.log")

		// Use derived log file in gluster fuse mount
		options = append(options, "log-file="+log)
	}
	if !hasLogLevel {
		options = append(options, "log-level=ERROR")
	}
	var addrlist []string
	if b.hosts == nil {
		return fmt.Errorf("glusterfs endpoint is nil in mounter")
	}
	addr := sets.String{}
	if b.hosts.Subsets != nil {
		for _, s := range b.hosts.Subsets {
			for _, a := range s.Addresses {
				if !addr.Has(a.IP) {
					addr.Insert(a.IP)
					addrlist = append(addrlist, a.IP)
				}
			}
		}
	}

	if (len(addrlist) > 0) && (addrlist[0] != "") {
		ip := addrlist[rand.Intn(len(addrlist))]

		// Add backup-volfile-servers and auto_unmount options.
		// When ip is also in backup-volfile-servers, there will be a warning:
		// "gf_remember_backup_volfile_server] 0-glusterfs: failed to set volfile server: File exists".
		addr.Delete(ip)
		backups := addr.List()
		// Avoid an invalid empty backup-volfile-servers option.
		if len(backups) > 0 {
			options = append(options, "backup-volfile-servers="+dstrings.Join(addrlist[:], ":"))
		}
		options = append(options, "auto_unmount")

		mountOptions := volutil.JoinMountOptions(b.mountOptions, options)
		// with `backup-volfile-servers` mount option in place, it is not required to
		// iterate over all the servers in the addrlist. A mount attempt with this option
		// will fetch all the servers mentioned in the backup-volfile-servers list.
		// Refer to backup-volfile-servers @ http://docs.gluster.org/en/latest/Administrator%20Guide/Setting%20Up%20Clients/

		errs = b.mounter.Mount(ip+":"+b.path, dir, "glusterfs", mountOptions)
		if errs == nil {
			klog.Infof("successfully mounted directory %s", dir)
			return nil
		}
		if dstrings.Contains(errs.Error(), "Invalid option auto_unmount") ||
			dstrings.Contains(errs.Error(), "Invalid argument") {
			// Give a try without `auto_unmount` mount option, because
			// it could be that gluster fuse client is older version and
			// mount.glusterfs is unaware of `auto_unmount`.
			noAutoMountOptions := make([]string, 0, len(mountOptions))
			for _, opt := range mountOptions {
				if opt != "auto_unmount" {
					noAutoMountOptions = append(noAutoMountOptions, opt)
				}
			}
			errs = b.mounter.Mount(ip+":"+b.path, dir, "glusterfs", noAutoMountOptions)
			if errs == nil {
				klog.Infof("successfully mounted %s", dir)
				return nil
			}
		}
	} else {
		return fmt.Errorf("failed to execute mount command:[no valid ipaddress found in endpoint address list]")
	}

	// Failed mount scenario.
	// Since glusterfs does not return error text
	// it all goes in a log file, we will read the log file
	logErr := readGlusterLog(log, b.pod.Name)
	if logErr != nil {
		return fmt.Errorf("mount failed: %v, the following error information was pulled from the glusterfs log to help diagnose this issue: %v", errs, logErr)
	}
	return fmt.Errorf("mount failed: %v", errs)

}

//getVolumeInfo returns 'path' and 'readonly' field values from the provided glusterfs spec.
func getVolumeInfo(spec *volume.Spec) (string, bool, error) {
	if spec.Volume != nil && spec.Volume.Glusterfs != nil {
		return spec.Volume.Glusterfs.Path, spec.Volume.Glusterfs.ReadOnly, nil
	} else if spec.PersistentVolume != nil &&
		spec.PersistentVolume.Spec.Glusterfs != nil {
		return spec.PersistentVolume.Spec.Glusterfs.Path, spec.ReadOnly, nil
	}
	return "", false, fmt.Errorf("spec does not reference a Glusterfs volume type")
}

func (plugin *glusterfsPlugin) NewProvisioner(options volume.VolumeOptions) (volume.Provisioner, error) {
	return plugin.newProvisionerInternal(options)
}

func (plugin *glusterfsPlugin) newProvisionerInternal(options volume.VolumeOptions) (volume.Provisioner, error) {
	return &glusterfsVolumeProvisioner{
		glusterfsMounter: &glusterfsMounter{
			glusterfs: &glusterfs{
				plugin: plugin,
			},
		},
		options: options,
	}, nil
}

type provisionerConfig struct {
	url                string
	user               string
	userKey            string
	secretNamespace    string
	secretName         string
	secretValue        string `datapolicy:"token"`
	clusterID          string
	gidMin             int
	gidMax             int
	volumeType         gapi.VolumeDurabilityInfo
	volumeOptions      []string
	volumeNamePrefix   string
	thinPoolSnapFactor float32
	customEpNamePrefix string
}

type glusterfsVolumeProvisioner struct {
	*glusterfsMounter
	provisionerConfig
	options volume.VolumeOptions
}

func convertGid(gidString string) (int, error) {
	gid64, err := strconv.ParseInt(gidString, 10, 32)
	if err != nil {
		return 0, fmt.Errorf("failed to parse gid %v: %v", gidString, err)
	}
	if gid64 < 0 {
		return 0, fmt.Errorf("negative GIDs %v are not allowed", gidString)
	}

	// ParseInt returns a int64, but since we parsed only
	// for 32 bit, we can cast to int without loss:
	gid := int(gid64)
	return gid, nil
}

func convertVolumeParam(volumeString string) (int, error) {
	count, err := strconv.Atoi(volumeString)
	if err != nil {
		return 0, fmt.Errorf("failed to parse volumestring %q: %v", volumeString, err)
	}

	if count < 0 {
		return 0, fmt.Errorf("negative values are not allowed")
	}
	return count, nil
}

func (plugin *glusterfsPlugin) NewDeleter(spec *volume.Spec) (volume.Deleter, error) {
	return plugin.newDeleterInternal(spec)
}

func (plugin *glusterfsPlugin) newDeleterInternal(spec *volume.Spec) (volume.Deleter, error) {
	if spec.PersistentVolume != nil && spec.PersistentVolume.Spec.Glusterfs == nil {
		return nil, fmt.Errorf("spec.PersistentVolume.Spec.Glusterfs is nil")
	}
	return &glusterfsVolumeDeleter{
		glusterfsMounter: &glusterfsMounter{
			glusterfs: &glusterfs{
				volName: spec.Name(),
				plugin:  plugin,
			},
			path: spec.PersistentVolume.Spec.Glusterfs.Path,
		},
		spec: spec.PersistentVolume,
	}, nil
}

type glusterfsVolumeDeleter struct {
	*glusterfsMounter
	provisionerConfig
	spec *v1.PersistentVolume
}

func (d *glusterfsVolumeDeleter) GetPath() string {
	name := glusterfsPluginName
	return d.plugin.host.GetPodVolumeDir(d.glusterfsMounter.glusterfs.pod.UID, utilstrings.EscapeQualifiedName(name), d.glusterfsMounter.glusterfs.volName)
}

// Traverse the PVs, fetching all the GIDs from those
// in a given storage class, and mark them in the table.
func (plugin *glusterfsPlugin) collectGids(className string, gidTable *MinMaxAllocator) error {
	kubeClient := plugin.host.GetKubeClient()
	if kubeClient == nil {
		return fmt.Errorf("failed to get kube client when collecting gids")
	}
	pvList, err := kubeClient.CoreV1().PersistentVolumes().List(context.TODO(), metav1.ListOptions{LabelSelector: labels.Everything().String()})
	if err != nil {
		return fmt.Errorf("failed to get existing persistent volumes")
	}
	for _, pv := range pvList.Items {
		if storagehelpers.GetPersistentVolumeClass(&pv) != className {
			continue
		}
		pvName := pv.ObjectMeta.Name
		gidStr, ok := pv.Annotations[volutil.VolumeGidAnnotationKey]
		if !ok {
			klog.Warningf("no GID found in pv %v", pvName)
			continue
		}
		gid, err := convertGid(gidStr)
		if err != nil {
			klog.Errorf("failed to parse gid %s: %v", gidStr, err)
			continue
		}
		_, err = gidTable.Allocate(gid)
		if err == ErrConflict {
			klog.Warningf("GID %v found in pv %v was already allocated", gid, pvName)
		} else if err != nil {
			return fmt.Errorf("failed to store gid %v found in pv %v: %v", gid, pvName, err)
		}
	}
	return nil
}

// Return the gid table for a storage class.
// - If this is the first time, fill it with all the gids
//   used in PVs of this storage class by traversing the PVs.
// - Adapt the range of the table to the current range of the SC.
func (plugin *glusterfsPlugin) getGidTable(className string, min int, max int) (*MinMaxAllocator, error) {
	plugin.gidTableLock.Lock()
	gidTable, ok := plugin.gidTable[className]
	plugin.gidTableLock.Unlock()

	if ok {
		err := gidTable.SetRange(min, max)
		if err != nil {
			return nil, err
		}
		return gidTable, nil
	}

	// create a new table and fill it
	newGidTable, err := NewMinMaxAllocator(0, absoluteGidMax)
	if err != nil {
		return nil, err
	}

	// collect gids with the full range
	err = plugin.collectGids(className, newGidTable)
	if err != nil {
		return nil, err
	}

	// and only reduce the range afterwards
	err = newGidTable.SetRange(min, max)
	if err != nil {
		return nil, err
	}

	// if in the meantime a table appeared, use it
	plugin.gidTableLock.Lock()
	defer plugin.gidTableLock.Unlock()
	gidTable, ok = plugin.gidTable[className]
	if ok {
		err = gidTable.SetRange(min, max)
		if err != nil {
			return nil, err
		}
		return gidTable, nil
	}

	plugin.gidTable[className] = newGidTable
	return newGidTable, nil
}

func (d *glusterfsVolumeDeleter) getGid() (int, bool, error) {
	gidStr, ok := d.spec.Annotations[volutil.VolumeGidAnnotationKey]
	if !ok {
		return 0, false, nil
	}
	gid, err := convertGid(gidStr)
	return gid, true, err
}

func (d *glusterfsVolumeDeleter) Delete() error {
	klog.V(2).Infof("delete volume %s", d.glusterfsMounter.path)
	volumeName := d.glusterfsMounter.path
	volumeID, err := getVolumeID(d.spec, volumeName)
	if err != nil {
		return fmt.Errorf("failed to get volumeID: %v", err)
	}
	class, err := volutil.GetClassForVolume(d.plugin.host.GetKubeClient(), d.spec)
	if err != nil {
		return err
	}
	cfg, err := parseClassParameters(class.Parameters, d.plugin.host.GetKubeClient())
	if err != nil {
		return err
	}
	d.provisionerConfig = *cfg
	klog.V(4).Infof("deleting volume %q", volumeID)
	gid, exists, err := d.getGid()
	if err != nil {
		klog.Error(err)
	} else if exists {
		gidTable, err := d.plugin.getGidTable(class.Name, cfg.gidMin, cfg.gidMax)
		if err != nil {
			return fmt.Errorf("failed to get gidTable: %v", err)
		}
		err = gidTable.Release(gid)
		if err != nil {
			return fmt.Errorf("failed to release gid %v: %v", gid, err)
		}
	}
	cli := filterClient(gcli.NewClient(d.url, d.user, d.secretValue), d.plugin.host.GetFilteredDialOptions())
	if cli == nil {
		klog.Errorf("failed to create glusterfs REST client")
		return fmt.Errorf("failed to create glusterfs REST client, REST server authentication failed")
	}
	err = cli.VolumeDelete(volumeID)
	if err != nil {
		if dstrings.TrimSpace(err.Error()) != errIDNotFound {
			// don't log error details from client calls in events
			klog.V(4).Infof("failed to delete volume %s: %v", volumeName, err)
			return fmt.Errorf("failed to delete volume: see kube-controller-manager.log for details")
		}
		klog.V(2).Infof("volume %s not present in heketi, ignoring", volumeName)
	}
	klog.V(2).Infof("volume %s deleted successfully", volumeName)

	//Deleter takes endpoint and namespace from pv spec.
	pvSpec := d.spec.Spec
	var dynamicEndpoint, dynamicNamespace string
	if pvSpec.ClaimRef == nil {
		klog.Errorf("ClaimRef is nil")
		return fmt.Errorf("ClaimRef is nil")
	}
	if pvSpec.ClaimRef.Namespace == "" {
		klog.Errorf("namespace is nil")
		return fmt.Errorf("namespace is nil")
	}
	dynamicNamespace = pvSpec.ClaimRef.Namespace
	if pvSpec.Glusterfs.EndpointsName != "" {
		dynamicEndpoint = pvSpec.Glusterfs.EndpointsName
	}
	klog.V(3).Infof("dynamic namespace and endpoint %v/%v", dynamicNamespace, dynamicEndpoint)
	err = d.deleteEndpointService(dynamicNamespace, dynamicEndpoint)
	if err != nil {
		klog.Errorf("failed to delete endpoint/service %v/%v: %v", dynamicNamespace, dynamicEndpoint, err)
	} else {
		klog.V(1).Infof("endpoint %v/%v is deleted successfully ", dynamicNamespace, dynamicEndpoint)
	}
	return nil
}

func filterClient(client *gcli.Client, opts *proxyutil.FilteredDialOptions) *gcli.Client {
	if opts == nil {
		return client
	}
	dialer := proxyutil.NewFilteredDialContext(nil, nil, opts)
	client.SetClientFunc(func(tlsConfig *tls.Config, checkRedirect gcli.CheckRedirectFunc) (gcli.HttpPerformer, error) {
		transport := http.DefaultTransport.(*http.Transport).Clone()
		transport.DialContext = dialer
		transport.TLSClientConfig = tlsConfig
		return &http.Client{Transport: transport, CheckRedirect: checkRedirect}, nil
	})
	return client
}

func (p *glusterfsVolumeProvisioner) Provision(selectedNode *v1.Node, allowedTopologies []v1.TopologySelectorTerm) (*v1.PersistentVolume, error) {
	if !volutil.ContainsAllAccessModes(p.plugin.GetAccessModes(), p.options.PVC.Spec.AccessModes) {
		return nil, fmt.Errorf("invalid AccessModes %v: only AccessModes %v are supported", p.options.PVC.Spec.AccessModes, p.plugin.GetAccessModes())
	}
	if p.options.PVC.Spec.Selector != nil {
		klog.V(4).Infof("not able to parse your claim Selector")
		return nil, fmt.Errorf("not able to parse your claim Selector")
	}
	if volutil.CheckPersistentVolumeClaimModeBlock(p.options.PVC) {
		return nil, fmt.Errorf("%s does not support block volume provisioning", p.plugin.GetPluginName())
	}
	klog.V(4).Infof("provision volume with options %v", p.options)
	scName := storagehelpers.GetPersistentVolumeClaimClass(p.options.PVC)
	cfg, err := parseClassParameters(p.options.Parameters, p.plugin.host.GetKubeClient())
	if err != nil {
		return nil, err
	}
	p.provisionerConfig = *cfg

	gidTable, err := p.plugin.getGidTable(scName, cfg.gidMin, cfg.gidMax)
	if err != nil {
		return nil, fmt.Errorf("failed to get gidTable: %v", err)
	}
	gid, _, err := gidTable.AllocateNext()
	if err != nil {
		klog.Errorf("failed to reserve GID from table: %v", err)
		return nil, fmt.Errorf("failed to reserve GID from table: %v", err)
	}
	klog.V(2).Infof("allocated GID %d for PVC %s", gid, p.options.PVC.Name)
	glusterfs, sizeGiB, volID, err := p.CreateVolume(gid)
	if err != nil {
		if releaseErr := gidTable.Release(gid); releaseErr != nil {
			klog.Errorf("error when releasing GID in storageclass %s: %v", scName, releaseErr)
		}
		return nil, fmt.Errorf("failed to create volume: %v", err)
	}
	mode := v1.PersistentVolumeFilesystem
	pv := new(v1.PersistentVolume)
	pv.Spec.PersistentVolumeSource.Glusterfs = glusterfs
	pv.Spec.PersistentVolumeReclaimPolicy = p.options.PersistentVolumeReclaimPolicy
	pv.Spec.AccessModes = p.options.PVC.Spec.AccessModes
	pv.Spec.VolumeMode = &mode
	if len(pv.Spec.AccessModes) == 0 {
		pv.Spec.AccessModes = p.plugin.GetAccessModes()
	}
	pv.Spec.MountOptions = p.options.MountOptions
	gidStr := strconv.FormatInt(int64(gid), 10)
	pv.Annotations = map[string]string{
		volutil.VolumeGidAnnotationKey:        gidStr,
		volutil.VolumeDynamicallyCreatedByKey: heketiAnn,
		glusterTypeAnn:                        "file",
		"Description":                         glusterDescAnn,
		heketiVolIDAnn:                        volID,
	}
	pv.Spec.Capacity = v1.ResourceList{
		v1.ResourceName(v1.ResourceStorage): resource.MustParse(fmt.Sprintf("%dGi", sizeGiB)),
	}
	return pv, nil
}

func (p *glusterfsVolumeProvisioner) CreateVolume(gid int) (r *v1.GlusterfsPersistentVolumeSource, size int, volID string, err error) {
	var clusterIDs []string
	customVolumeName := ""
	epServiceName := ""
	kubeClient := p.plugin.host.GetKubeClient()
	if kubeClient == nil {
		return nil, 0, "", fmt.Errorf("failed to get kube client to update endpoint")
	}
	if len(p.provisionerConfig.customEpNamePrefix) == 0 {
		epServiceName = string(p.options.PVC.UID)
	} else {
		epServiceName = p.provisionerConfig.customEpNamePrefix + "-" + string(p.options.PVC.UID)
	}
	epNamespace := p.options.PVC.Namespace
	endpoint, service, err := p.createOrGetEndpointService(epNamespace, epServiceName, p.options.PVC)
	if err != nil {
		klog.Errorf("failed to create endpoint/service %v/%v: %v", epNamespace, epServiceName, err)
		return nil, 0, "", fmt.Errorf("failed to create endpoint/service %v/%v: %v", epNamespace, epServiceName, err)
	}
	klog.V(3).Infof("dynamic endpoint %v and service %v ", endpoint, service)
	capacity := p.options.PVC.Spec.Resources.Requests[v1.ResourceName(v1.ResourceStorage)]

	// GlusterFS/heketi creates volumes in units of GiB.
	sz, err := volumehelpers.RoundUpToGiBInt(capacity)
	if err != nil {
		return nil, 0, "", err
	}
	klog.V(2).Infof("create volume of size %dGiB", sz)
	if p.url == "" {
		return nil, 0, "", fmt.Errorf("failed to create glusterfs REST client, REST URL is empty")
	}
	cli := filterClient(gcli.NewClient(p.url, p.user, p.secretValue), p.plugin.host.GetFilteredDialOptions())
	if cli == nil {
		return nil, 0, "", fmt.Errorf("failed to create glusterfs REST client, REST server authentication failed")
	}
	if p.provisionerConfig.clusterID != "" {
		clusterIDs = dstrings.Split(p.clusterID, ",")
		klog.V(4).Infof("provided clusterIDs %v", clusterIDs)
	}

	if p.provisionerConfig.volumeNamePrefix != "" {
		customVolumeName = fmt.Sprintf("%s_%s_%s_%s", p.provisionerConfig.volumeNamePrefix, p.options.PVC.Namespace, p.options.PVC.Name, uuid.NewUUID())
	}
	gid64 := int64(gid)
	snaps := struct {
		Enable bool    `json:"enable"`
		Factor float32 `json:"factor"`
	}{
		true,
		p.provisionerConfig.thinPoolSnapFactor,
	}
	volumeReq := &gapi.VolumeCreateRequest{Size: sz, Name: customVolumeName, Clusters: clusterIDs, Gid: gid64, Durability: p.volumeType, GlusterVolumeOptions: p.volumeOptions, Snapshot: snaps}
	volume, err := cli.VolumeCreate(volumeReq)
	if err != nil {
		// don't log error details from client calls in events
		klog.V(4).Infof("failed to create volume: %v", err)
		return nil, 0, "", fmt.Errorf("failed to create volume: see kube-controller-manager.log for details")
	}
	klog.V(1).Infof("volume with size %d and name %s created", volume.Size, volume.Name)
	volID = volume.Id
	dynamicHostIps, err := getClusterNodes(cli, volume.Cluster)
	if err != nil {
		return nil, 0, "", fmt.Errorf("failed to get cluster nodes for volume %s: %v", volume, err)
	}
	addrlist := make([]v1.EndpointAddress, len(dynamicHostIps))
	for i, v := range dynamicHostIps {
		addrlist[i].IP = v
	}
	subset := make([]v1.EndpointSubset, 1)
	ports := []v1.EndpointPort{{Port: 1, Protocol: "TCP"}}
	endpoint.Subsets = subset
	endpoint.Subsets[0].Addresses = addrlist
	endpoint.Subsets[0].Ports = ports
	_, err = kubeClient.CoreV1().Endpoints(epNamespace).Update(context.TODO(), endpoint, metav1.UpdateOptions{})
	if err != nil {
		deleteErr := cli.VolumeDelete(volume.Id)
		if deleteErr != nil {
			// don't log error details from client calls in events
			klog.V(4).Infof("failed to delete volume: %v, manual deletion of the volume required", deleteErr)
		}
		klog.V(3).Infof("failed to update endpoint, deleting %s", endpoint)
		err = kubeClient.CoreV1().Services(epNamespace).Delete(context.TODO(), epServiceName, metav1.DeleteOptions{})
		if err != nil && errors.IsNotFound(err) {
			klog.V(1).Infof("service %s does not exist in namespace %s", epServiceName, epNamespace)
			err = nil
		}
		if err != nil {
			klog.Errorf("failed to delete service %s/%s: %v", epNamespace, epServiceName, err)
		}
		klog.V(1).Infof("service/endpoint: %s/%s deleted successfully", epNamespace, epServiceName)
		return nil, 0, "", fmt.Errorf("failed to update endpoint %s: %v", endpoint, err)
	}
	klog.V(3).Infof("endpoint %s updated successfully", endpoint)
	return &v1.GlusterfsPersistentVolumeSource{
		EndpointsName:      endpoint.Name,
		EndpointsNamespace: &epNamespace,
		Path:               volume.Name,
		ReadOnly:           false,
	}, sz, volID, nil
}

// createOrGetEndpointService() makes sure an endpoint and service
// exist for the given namespace, PVC name, endpoint name
// I.e. the endpoint or service is only created
// if it does not exist yet.
func (p *glusterfsVolumeProvisioner) createOrGetEndpointService(namespace string, epServiceName string, pvc *v1.PersistentVolumeClaim) (endpoint *v1.Endpoints, service *v1.Service, err error) {
	pvcNameOrID := ""
	if len(pvc.Name) >= 63 {
		pvcNameOrID = string(pvc.UID)
	} else {
		pvcNameOrID = pvc.Name
	}
	endpoint = &v1.Endpoints{
		ObjectMeta: metav1.ObjectMeta{
			Namespace: namespace,
			Name:      epServiceName,
			Labels: map[string]string{
				"gluster.kubernetes.io/provisioned-for-pvc": pvcNameOrID,
			},
		},
	}
	kubeClient := p.plugin.host.GetKubeClient()
	if kubeClient == nil {
		return nil, nil, fmt.Errorf("failed to get kube client when creating endpoint service")
	}
	_, err = kubeClient.CoreV1().Endpoints(namespace).Create(context.TODO(), endpoint, metav1.CreateOptions{})
	if err != nil && errors.IsAlreadyExists(err) {
		klog.V(1).Infof("endpoint %s already exist in namespace %s", endpoint, namespace)
		err = nil
	}
	if err != nil {
		klog.Errorf("failed to create endpoint: %v", err)
		return nil, nil, fmt.Errorf("failed to create endpoint: %v", err)
	}
	service = &v1.Service{
		ObjectMeta: metav1.ObjectMeta{
			Name:      epServiceName,
			Namespace: namespace,
			Labels: map[string]string{
				"gluster.kubernetes.io/provisioned-for-pvc": pvcNameOrID,
			},
		},
		Spec: v1.ServiceSpec{
			Ports: []v1.ServicePort{
				{Protocol: "TCP", Port: 1}}}}
	_, err = kubeClient.CoreV1().Services(namespace).Create(context.TODO(), service, metav1.CreateOptions{})
	if err != nil && errors.IsAlreadyExists(err) {
		klog.V(1).Infof("service %s already exist in namespace %s", service, namespace)
		err = nil
	}
	if err != nil {
		klog.Errorf("failed to create service: %v", err)
		return nil, nil, fmt.Errorf("error creating service: %v", err)
	}
	return endpoint, service, nil
}

func (d *glusterfsVolumeDeleter) deleteEndpointService(namespace string, epServiceName string) (err error) {
	kubeClient := d.plugin.host.GetKubeClient()
	if kubeClient == nil {
		return fmt.Errorf("failed to get kube client when deleting endpoint service")
	}
	err = kubeClient.CoreV1().Services(namespace).Delete(context.TODO(), epServiceName, metav1.DeleteOptions{})
	if err != nil {
		return fmt.Errorf("failed to delete service %s/%s: %v", namespace, epServiceName, err)
	}
	klog.V(1).Infof("service/endpoint: %s/%s deleted successfully", namespace, epServiceName)
	return nil
}

// parseSecret finds a given Secret instance and reads user password from it.
func parseSecret(namespace, secretName string, kubeClient clientset.Interface) (string, error) {
	secretMap, err := volutil.GetSecretForPV(namespace, secretName, glusterfsPluginName, kubeClient)
	if err != nil {
		klog.Errorf("failed to get secret: %s/%s: %v", namespace, secretName, err)
		return "", fmt.Errorf("failed to get secret %s/%s: %v", namespace, secretName, err)
	}
	if len(secretMap) == 0 {
		return "", fmt.Errorf("empty secret map")
	}
	secret := ""
	for k, v := range secretMap {
		if k == secretKeyName {
			return v, nil
		}
		secret = v
	}

	// If not found, the last secret in the map wins as done before
	return secret, nil
}

// getClusterNodes() returns the cluster nodes of a given cluster
func getClusterNodes(cli *gcli.Client, cluster string) (dynamicHostIps []string, err error) {
	clusterinfo, err := cli.ClusterInfo(cluster)
	if err != nil {
		// don't log error details from client calls in events
		klog.V(4).Infof("failed to get cluster details: %v", err)
		return nil, fmt.Errorf("failed to get cluster details: see kube-controller-manager.log for details")
	}

	// For the dynamically provisioned volume, we gather the list of node IPs
	// of the cluster on which provisioned volume belongs to, as there can be multiple
	// clusters.
	for _, node := range clusterinfo.Nodes {
		nodeInfo, err := cli.NodeInfo(string(node))
		if err != nil {
			// don't log error details from client calls in events
			klog.V(4).Infof("failed to get host ipaddress: %v", err)
			return nil, fmt.Errorf("failed to get host ipaddress: see kube-controller-manager.log for details")
		}
		ipaddr := dstrings.Join(nodeInfo.NodeAddRequest.Hostnames.Storage, "")
		// IP validates if a string is a valid IP address.
		ip := net.ParseIP(ipaddr)
		if ip == nil {
			return nil, fmt.Errorf("glusterfs server node ip address %s must be a valid IP address, (e.g. 10.9.8.7)", ipaddr)
		}
		dynamicHostIps = append(dynamicHostIps, ipaddr)
	}
	klog.V(3).Infof("host list :%v", dynamicHostIps)
	if len(dynamicHostIps) == 0 {
		return nil, fmt.Errorf("no hosts found: %v", err)
	}
	return dynamicHostIps, nil
}

// parseClassParameters parses StorageClass parameters.
func parseClassParameters(params map[string]string, kubeClient clientset.Interface) (*provisionerConfig, error) {
	var cfg provisionerConfig
	var err error
	cfg.gidMin = defaultGidMin
	cfg.gidMax = defaultGidMax
	cfg.customEpNamePrefix = dynamicEpSvcPrefix

	authEnabled := true
	parseVolumeType := ""
	parseVolumeOptions := ""
	parseVolumeNamePrefix := ""
	parseThinPoolSnapFactor := ""

	//thin pool snap factor default to 1.0
	cfg.thinPoolSnapFactor = float32(1.0)

	for k, v := range params {
		switch dstrings.ToLower(k) {
		case "resturl":
			cfg.url = v
		case "restuser":
			cfg.user = v
		case "restuserkey":
			cfg.userKey = v
		case "secretname":
			cfg.secretName = v
		case "secretnamespace":
			cfg.secretNamespace = v
		case "clusterid":
			if len(v) != 0 {
				cfg.clusterID = v
			}
		case "restauthenabled":
			authEnabled = dstrings.ToLower(v) == "true"
		case "gidmin":
			parseGidMin, err := convertGid(v)
			if err != nil {
				return nil, fmt.Errorf("invalid gidMin value %q for volume plugin %s", k, glusterfsPluginName)
			}
			if parseGidMin < absoluteGidMin {
				return nil, fmt.Errorf("gidMin must be >= %v", absoluteGidMin)
			}
			if parseGidMin > absoluteGidMax {
				return nil, fmt.Errorf("gidMin must be <= %v", absoluteGidMax)
			}
			cfg.gidMin = parseGidMin
		case "gidmax":
			parseGidMax, err := convertGid(v)
			if err != nil {
				return nil, fmt.Errorf("invalid gidMax value %q for volume plugin %s", k, glusterfsPluginName)
			}
			if parseGidMax < absoluteGidMin {
				return nil, fmt.Errorf("gidMax must be >= %v", absoluteGidMin)
			}
			if parseGidMax > absoluteGidMax {
				return nil, fmt.Errorf("gidMax must be <= %v", absoluteGidMax)
			}
			cfg.gidMax = parseGidMax
		case "volumetype":
			parseVolumeType = v

		case "volumeoptions":
			if len(v) != 0 {
				parseVolumeOptions = v
			}
		case "volumenameprefix":
			if len(v) != 0 {
				parseVolumeNamePrefix = v
			}
		case "snapfactor":
			if len(v) != 0 {
				parseThinPoolSnapFactor = v
			}
		case "customepnameprefix":
			// If the string has > 'maxCustomEpNamePrefixLen' chars, the final endpoint name will
			// exceed the limitation of 63 chars, so fail if prefix is > 'maxCustomEpNamePrefixLen'
			// characters. This is only applicable for 'customepnameprefix' string and default ep name
			// string will always pass.
			if len(v) <= maxCustomEpNamePrefixLen {
				cfg.customEpNamePrefix = v
			} else {
				return nil, fmt.Errorf("'customepnameprefix' value should be < %d characters", maxCustomEpNamePrefixLen)
			}
		default:
			return nil, fmt.Errorf("invalid option %q for volume plugin %s", k, glusterfsPluginName)
		}
	}
	if len(cfg.url) == 0 {
		return nil, fmt.Errorf("StorageClass for provisioner %s must contain 'resturl' parameter", glusterfsPluginName)
	}
	if len(parseVolumeType) == 0 {
		cfg.volumeType = gapi.VolumeDurabilityInfo{Type: gapi.DurabilityReplicate, Replicate: gapi.ReplicaDurability{Replica: replicaCount}}
	} else {
		parseVolumeTypeInfo := dstrings.Split(parseVolumeType, ":")
		switch parseVolumeTypeInfo[0] {
		case "replicate":
			if len(parseVolumeTypeInfo) >= 2 {
				newReplicaCount, err := convertVolumeParam(parseVolumeTypeInfo[1])
				if err != nil {
					return nil, fmt.Errorf("error parsing volumeType %q: %s", parseVolumeTypeInfo[1], err)
				}
				cfg.volumeType = gapi.VolumeDurabilityInfo{Type: gapi.DurabilityReplicate, Replicate: gapi.ReplicaDurability{Replica: newReplicaCount}}
			} else {
				cfg.volumeType = gapi.VolumeDurabilityInfo{Type: gapi.DurabilityReplicate, Replicate: gapi.ReplicaDurability{Replica: replicaCount}}
			}
		case "disperse":
			if len(parseVolumeTypeInfo) >= 3 {
				newDisperseData, err := convertVolumeParam(parseVolumeTypeInfo[1])
				if err != nil {
					return nil, fmt.Errorf("error parsing volumeType %q: %s", parseVolumeTypeInfo[1], err)
				}
				newDisperseRedundancy, err := convertVolumeParam(parseVolumeTypeInfo[2])
				if err != nil {
					return nil, fmt.Errorf("error parsing volumeType %q: %s", parseVolumeTypeInfo[2], err)
				}
				cfg.volumeType = gapi.VolumeDurabilityInfo{Type: gapi.DurabilityEC, Disperse: gapi.DisperseDurability{Data: newDisperseData, Redundancy: newDisperseRedundancy}}
			} else {
				return nil, fmt.Errorf("StorageClass for provisioner %q must have data:redundancy count set for disperse volumes in storage class option '%s'", glusterfsPluginName, "volumetype")
			}
		case "none":
			cfg.volumeType = gapi.VolumeDurabilityInfo{Type: gapi.DurabilityDistributeOnly}
		default:
			return nil, fmt.Errorf("error parsing value for option 'volumetype' for volume plugin %s", glusterfsPluginName)
		}
	}
	if !authEnabled {
		cfg.user = ""
		cfg.secretName = ""
		cfg.secretNamespace = ""
		cfg.userKey = ""
		cfg.secretValue = ""
	}

	if len(cfg.secretName) != 0 || len(cfg.secretNamespace) != 0 {
		// secretName + Namespace has precedence over userKey
		if len(cfg.secretName) != 0 && len(cfg.secretNamespace) != 0 {
			cfg.secretValue, err = parseSecret(cfg.secretNamespace, cfg.secretName, kubeClient)
			if err != nil {
				return nil, err
			}
		} else {
			return nil, fmt.Errorf("StorageClass for provisioner %q must have secretNamespace and secretName either both set or both empty", glusterfsPluginName)
		}
	} else {
		cfg.secretValue = cfg.userKey
	}
	if cfg.gidMin > cfg.gidMax {
		return nil, fmt.Errorf("storageClass for provisioner %q must have gidMax value >= gidMin", glusterfsPluginName)
	}
	if len(parseVolumeOptions) != 0 {
		volOptions := dstrings.Split(parseVolumeOptions, ",")
		if len(volOptions) == 0 {
			return nil, fmt.Errorf("storageClass for provisioner %q must have valid (for e.g., 'client.ssl on') volume option", glusterfsPluginName)
		}
		cfg.volumeOptions = volOptions
	}
	if len(parseVolumeNamePrefix) != 0 {
		if dstrings.Contains(parseVolumeNamePrefix, "_") {
			return nil, fmt.Errorf("storageclass parameter 'volumenameprefix' should not contain '_' in its value")
		}
		cfg.volumeNamePrefix = parseVolumeNamePrefix
	}
	if len(parseThinPoolSnapFactor) != 0 {
		thinPoolSnapFactor, err := strconv.ParseFloat(parseThinPoolSnapFactor, 32)
		if err != nil {
			return nil, fmt.Errorf("failed to convert snapfactor %v to float: %v", parseThinPoolSnapFactor, err)
		}
		if thinPoolSnapFactor < 1.0 || thinPoolSnapFactor > 100.0 {
			return nil, fmt.Errorf("invalid snapshot factor %v, the value must be between 1 to 100", thinPoolSnapFactor)
		}
		cfg.thinPoolSnapFactor = float32(thinPoolSnapFactor)
	}
	return &cfg, nil
}

// getVolumeID returns volumeID from the PV or volumename.
func getVolumeID(pv *v1.PersistentVolume, volumeName string) (string, error) {
	volumeID := ""

	// Get volID from pvspec if available, else fill it from volumename.
	if pv != nil {
		if pv.Annotations[heketiVolIDAnn] != "" {
			volumeID = pv.Annotations[heketiVolIDAnn]
		} else {
			volumeID = dstrings.TrimPrefix(volumeName, volPrefix)
		}
	} else {
		return volumeID, fmt.Errorf("provided PV spec is nil")
	}
	if volumeID == "" {
		return volumeID, fmt.Errorf("volume ID is empty")
	}
	return volumeID, nil
}

func (plugin *glusterfsPlugin) ExpandVolumeDevice(spec *volume.Spec, newSize resource.Quantity, oldSize resource.Quantity) (resource.Quantity, error) {
	pvSpec := spec.PersistentVolume.Spec
	volumeName := pvSpec.Glusterfs.Path
	klog.V(2).Infof("received request to expand volume %s", volumeName)
	volumeID, err := getVolumeID(spec.PersistentVolume, volumeName)
	if err != nil {
		return oldSize, fmt.Errorf("failed to get volumeID for volume %s: %v", volumeName, err)
	}
	//Get details of StorageClass.
	class, err := volutil.GetClassForVolume(plugin.host.GetKubeClient(), spec.PersistentVolume)
	if err != nil {
		return oldSize, err
	}
	cfg, err := parseClassParameters(class.Parameters, plugin.host.GetKubeClient())
	if err != nil {
		return oldSize, err
	}
	klog.V(4).Infof("expanding volume: %q", volumeID)

	//Create REST server connection
	cli := filterClient(gcli.NewClient(cfg.url, cfg.user, cfg.secretValue), plugin.host.GetFilteredDialOptions())
	if cli == nil {
		klog.Errorf("failed to create glusterfs REST client")
		return oldSize, fmt.Errorf("failed to create glusterfs REST client, REST server authentication failed")
	}

	// Find out delta size
	expansionSize := newSize
	expansionSize.Sub(oldSize)
	expansionSizeGiB, err := volumehelpers.RoundUpToGiBInt(expansionSize)
	if err != nil {
		return oldSize, err
	}

	// Find out requested Size
	requestGiB, err := volumehelpers.RoundUpToGiB(newSize)
	if err != nil {
		return oldSize, err
	}

	//Check the existing volume size
	currentVolumeInfo, err := cli.VolumeInfo(volumeID)
	if err != nil {
		// don't log error details from client calls in events
		klog.V(4).Infof("error when fetching details of volume %s: %v", volumeName, err)
		return oldSize, fmt.Errorf("failed to get volume info %s: see kube-controller-manager.log for details", volumeName)
	}
	if int64(currentVolumeInfo.Size) >= requestGiB {
		return newSize, nil
	}

	// Make volume expansion request
	volumeExpandReq := &gapi.VolumeExpandRequest{Size: expansionSizeGiB}

	// Expand the volume
	volumeInfoRes, err := cli.VolumeExpand(volumeID, volumeExpandReq)
	if err != nil {
		// don't log error details from client calls in events
		klog.V(4).Infof("failed to expand volume %s: %v", volumeName, err)
		return oldSize, fmt.Errorf("failed to expand volume: see kube-controller-manager.log for details")
	}
	klog.V(2).Infof("volume %s expanded to new size %d successfully", volumeName, volumeInfoRes.Size)
	newVolumeSize := resource.MustParse(fmt.Sprintf("%dGi", volumeInfoRes.Size))
	return newVolumeSize, nil
}
