kubernetes/pkg/scheduler/framework/plugins/nodevolumelimits/csi.go

/*
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 nodevolumelimits

import (
	"context"
	"fmt"

	v1 "k8s.io/api/core/v1"
	storagev1 "k8s.io/api/storage/v1"
	apierrors "k8s.io/apimachinery/pkg/api/errors"
	"k8s.io/apimachinery/pkg/labels"
	"k8s.io/apimachinery/pkg/runtime"
	"k8s.io/apimachinery/pkg/util/rand"
	corelisters "k8s.io/client-go/listers/core/v1"
	storagelisters "k8s.io/client-go/listers/storage/v1"
	ephemeral "k8s.io/component-helpers/storage/ephemeral"
	storagehelpers "k8s.io/component-helpers/storage/volume"
	csitrans "k8s.io/csi-translation-lib"
	"k8s.io/klog/v2"
	fwk "k8s.io/kube-scheduler/framework"
	"k8s.io/kubernetes/pkg/scheduler/framework/plugins/feature"
	"k8s.io/kubernetes/pkg/scheduler/framework/plugins/names"
	"k8s.io/kubernetes/pkg/scheduler/util"
)

const (
	// ErrReasonMaxVolumeCountExceeded is used for MaxVolumeCount predicate error.
	ErrReasonMaxVolumeCountExceeded = "node(s) exceed max volume count"
)

// InTreeToCSITranslator contains methods required to check migratable status
// and perform translations from InTree PV's to CSI
type InTreeToCSITranslator interface {
	IsPVMigratable(pv *v1.PersistentVolume) bool
	IsInlineMigratable(vol *v1.Volume) bool
	IsMigratableIntreePluginByName(inTreePluginName string) bool
	GetInTreePluginNameFromSpec(pv *v1.PersistentVolume, vol *v1.Volume) (string, error)
	GetCSINameFromInTreeName(pluginName string) (string, error)
	TranslateInTreePVToCSI(logger klog.Logger, pv *v1.PersistentVolume) (*v1.PersistentVolume, error)
	TranslateInTreeInlineVolumeToCSI(logger klog.Logger, volume *v1.Volume, podNamespace string) (*v1.PersistentVolume, error)
}

// CSILimits is a plugin that checks node volume limits.
type CSILimits struct {
	csiManager      fwk.CSIManager
	pvLister        corelisters.PersistentVolumeLister
	pvcLister       corelisters.PersistentVolumeClaimLister
	scLister        storagelisters.StorageClassLister
	vaLister        storagelisters.VolumeAttachmentLister
	csiDriverLister storagelisters.CSIDriverLister

	enableCSIMigrationPortworx bool
	randomVolumeIDPrefix       string
	enableVolumeLimitScaling   bool
	translator                 InTreeToCSITranslator
}

var _ fwk.PreFilterPlugin = &CSILimits{}
var _ fwk.FilterPlugin = &CSILimits{}
var _ fwk.EnqueueExtensions = &CSILimits{}
var _ fwk.SignPlugin = &CSILimits{}

// CSIName is the name of the plugin used in the plugin registry and configurations.
const CSIName = names.NodeVolumeLimits

// Name returns name of the plugin. It is used in logs, etc.
func (pl *CSILimits) Name() string {
	return CSIName
}

// EventsToRegister returns the possible events that may make a Pod.
// failed by this plugin schedulable.
func (pl *CSILimits) EventsToRegister(_ context.Context) ([]fwk.ClusterEventWithHint, error) {
	return []fwk.ClusterEventWithHint{
		// We don't register any `QueueingHintFn` intentionally
		// because any new CSINode could make pods that were rejected by CSI volumes schedulable.
		{Event: fwk.ClusterEvent{Resource: fwk.CSINode, ActionType: fwk.Add}},
		{Event: fwk.ClusterEvent{Resource: fwk.CSINode, ActionType: fwk.Update}, QueueingHintFn: pl.isSchedulableAfterCSINodeUpdated},
		{Event: fwk.ClusterEvent{Resource: fwk.Pod, ActionType: fwk.Delete}, QueueingHintFn: pl.isSchedulableAfterPodDeleted},
		{Event: fwk.ClusterEvent{Resource: fwk.PersistentVolumeClaim, ActionType: fwk.Add}, QueueingHintFn: pl.isSchedulableAfterPVCAdded},
		{Event: fwk.ClusterEvent{Resource: fwk.VolumeAttachment, ActionType: fwk.Delete}, QueueingHintFn: pl.isSchedulableAfterVolumeAttachmentDeleted},
	}, nil
}

func (pl *CSILimits) isSchedulableAfterPodDeleted(logger klog.Logger, pod *v1.Pod, oldObj, newObj interface{}) (fwk.QueueingHint, error) {
	deletedPod, _, err := util.As[*v1.Pod](oldObj, newObj)
	if err != nil {
		return fwk.Queue, fmt.Errorf("unexpected objects in isSchedulableAfterPodDeleted: %w", err)
	}

	if len(deletedPod.Spec.Volumes) == 0 {
		return fwk.QueueSkip, nil
	}

	if deletedPod.Spec.NodeName == "" && deletedPod.Status.NominatedNodeName == "" {
		return fwk.QueueSkip, nil
	}

	for _, vol := range deletedPod.Spec.Volumes {
		if vol.PersistentVolumeClaim != nil || vol.Ephemeral != nil || pl.translator.IsInlineMigratable(&vol) {
			return fwk.Queue, nil
		}
	}

	logger.V(5).Info("The deleted pod does not impact the scheduling of the unscheduled pod", "pod", klog.KObj(pod), "deletedPod", klog.KObj(deletedPod))
	return fwk.QueueSkip, nil
}

func (pl *CSILimits) isSchedulableAfterPVCAdded(logger klog.Logger, pod *v1.Pod, oldObj, newObj interface{}) (fwk.QueueingHint, error) {
	_, addedPvc, err := util.As[*v1.PersistentVolumeClaim](oldObj, newObj)
	if err != nil {
		return fwk.Queue, fmt.Errorf("unexpected objects in isSchedulableAfterPVCAdded: %w", err)
	}

	if addedPvc.Namespace != pod.Namespace {
		return fwk.QueueSkip, nil
	}

	for _, volumes := range pod.Spec.Volumes {
		var pvcName string
		switch {
		case volumes.PersistentVolumeClaim != nil:
			pvcName = volumes.PersistentVolumeClaim.ClaimName
		case volumes.Ephemeral != nil:
			pvcName = ephemeral.VolumeClaimName(pod, &volumes)
		default:
			// Volume is not using a PVC, ignore
			continue
		}

		if pvcName == addedPvc.Name {
			logger.V(5).Info("PVC that is referred from the pod was created, which might make this pod schedulable", "pod", klog.KObj(pod), "PVC", klog.KObj(addedPvc))
			return fwk.Queue, nil
		}
	}

	logger.V(5).Info("PVC irrelevant to the Pod was created, which doesn't make this pod schedulable", "pod", klog.KObj(pod), "PVC", klog.KObj(addedPvc))
	return fwk.QueueSkip, nil
}

func (pl *CSILimits) isSchedulableAfterVolumeAttachmentDeleted(logger klog.Logger, pod *v1.Pod, oldObj, newObj interface{}) (fwk.QueueingHint, error) {
	deletedVolumeAttachment, _, err := util.As[*storagev1.VolumeAttachment](oldObj, newObj)
	if err != nil {
		return fwk.Queue, fmt.Errorf("unexpected objects in isSchedulableAfterVolumeAttachmentDeleted: %w", err)
	}

	for _, vol := range pod.Spec.Volumes {
		// Check if the pod volume uses a PVC
		// If it does, return Queue
		if vol.PersistentVolumeClaim != nil {
			logger.V(5).Info("Pod volume uses PersistentVolumeClaim, which might make this pod schedulable due to VolumeAttachment deletion", "pod", klog.KObj(pod), "volumeAttachment", klog.KObj(deletedVolumeAttachment), "volume", vol.Name)
			return fwk.Queue, nil
		}

		if !pl.translator.IsInlineMigratable(&vol) {
			continue
		}

		translatedPV, err := pl.translator.TranslateInTreeInlineVolumeToCSI(logger, &vol, pod.Namespace)
		if err != nil || translatedPV == nil {
			return fwk.Queue, fmt.Errorf("converting volume(%s) from inline to csi: %w", vol.Name, err)
		}

		if translatedPV.Spec.CSI != nil && deletedVolumeAttachment.Spec.Attacher == translatedPV.Spec.CSI.Driver {
			// deleted VolumeAttachment Attacher matches the translated PV CSI driver
			logger.V(5).Info("Pod volume is an Inline Migratable volume that matches the CSI driver, which might make this pod schedulable due to VolumeAttachment deletion",
				"pod", klog.KObj(pod), "volumeAttachment", klog.KObj(deletedVolumeAttachment),
				"volume", vol.Name, "csiDriver", translatedPV.Spec.CSI.Driver,
			)
			return fwk.Queue, nil
		}
	}

	logger.V(5).Info("the VolumeAttachment deletion wouldn't make this pod schedulable because the pod has no volume related to a deleted VolumeAttachment",
		"pod", klog.KObj(pod), "volumeAttachment", klog.KObj(deletedVolumeAttachment))
	return fwk.QueueSkip, nil
}

func (pl *CSILimits) isSchedulableAfterCSINodeUpdated(logger klog.Logger, pod *v1.Pod, oldObj, newObj interface{}) (fwk.QueueingHint, error) {
	oldCSINode, newCSINode, err := util.As[*storagev1.CSINode](oldObj, newObj)
	if err != nil {
		return fwk.Queue, fmt.Errorf("unexpected objects in isSchedulableAfterCSINodeUpdated: %w", err)
	}

	oldLimits := make(map[string]int32)
	for _, d := range oldCSINode.Spec.Drivers {
		var count int32
		if d.Allocatable != nil && d.Allocatable.Count != nil {
			count = *d.Allocatable.Count
		}
		oldLimits[d.Name] = count
	}

	// Compare new driver limits vs. old. If limit increased, queue pod.
	for _, d := range newCSINode.Spec.Drivers {
		var oldLimit int32
		if val, exists := oldLimits[d.Name]; exists {
			oldLimit = val
		}
		newLimit := int32(0)
		if d.Allocatable != nil && d.Allocatable.Count != nil {
			newLimit = *d.Allocatable.Count
		}

		if newLimit > oldLimit {
			logger.V(5).Info("CSINode driver limit increased, might make this pod schedulable",
				"pod", klog.KObj(pod),
				"driver", d.Name,
				"oldLimit", oldLimit,
				"newLimit", newLimit,
			)
			return fwk.Queue, nil
		}
	}

	// If no driver limit was increased, skip queueing.
	return fwk.QueueSkip, nil
}

// PreFilter invoked at the prefilter extension point
//
// If the pod haven't those types of volumes, we'll skip the Filter phase
func (pl *CSILimits) PreFilter(ctx context.Context, _ fwk.CycleState, pod *v1.Pod, _ []fwk.NodeInfo) (*fwk.PreFilterResult, *fwk.Status) {
	volumes := pod.Spec.Volumes
	for i := range volumes {
		vol := &volumes[i]
		if vol.PersistentVolumeClaim != nil || vol.Ephemeral != nil || pl.translator.IsInlineMigratable(vol) {
			return nil, nil
		}
	}

	return nil, fwk.NewStatus(fwk.Skip)
}

// PreFilterExtensions returns prefilter extensions, pod add and remove.
func (pl *CSILimits) PreFilterExtensions() fwk.PreFilterExtensions {
	return nil
}

// Filter invoked at the filter extension point.
func (pl *CSILimits) Filter(ctx context.Context, _ fwk.CycleState, pod *v1.Pod, nodeInfo fwk.NodeInfo) *fwk.Status {
	// If the new pod doesn't have any volume attached to it, the predicate will always be true
	if len(pod.Spec.Volumes) == 0 {
		return nil
	}

	node := nodeInfo.Node()

	logger := klog.FromContext(ctx)

	csiNode, err := pl.csiManager.CSINodes().Get(node.Name)
	if err != nil {
		// TODO: return the error once CSINode is created by default (2 releases)
		logger.V(5).Info("Could not get a CSINode object for the node", "node", klog.KObj(node), "err", err)
	}

	// Count CSI volumes from the new pod
	newVolumes := make(map[string]string)
	if err := pl.filterAttachableVolumes(logger, pod, csiNode, true /* new pod */, newVolumes); err != nil {
		if apierrors.IsNotFound(err) {
			// PVC is not found. This Pod will never be schedulable until PVC is created.
			return fwk.NewStatus(fwk.UnschedulableAndUnresolvable, err.Error())
		}
		return fwk.AsStatus(err)
	}

	// If the pod doesn't have any new CSI volumes, the predicate will always be true
	if len(newVolumes) == 0 {
		return nil
	}

	if pl.enableVolumeLimitScaling {
		for _, driverName := range newVolumes {
			driverInstalled, err := pl.checkCSIDriverOnNode(driverName, csiNode)
			if err != nil {
				return fwk.AsStatus(err)
			}
			if !driverInstalled {
				driverNotInstalledMsg := fmt.Sprintf("%s CSI driver is not installed on the node", driverName)
				return fwk.NewStatus(fwk.Unschedulable, driverNotInstalledMsg)
			}
		}
	}

	// If the node doesn't have volume limits, the predicate will always be true
	nodeVolumeLimits := getVolumeLimits(csiNode)
	if len(nodeVolumeLimits) == 0 {
		return nil
	}

	// Count CSI volumes from existing pods
	attachedVolumes := make(map[string]string)
	for _, existingPod := range nodeInfo.GetPods() {
		if err := pl.filterAttachableVolumes(logger, existingPod.GetPod(), csiNode, false /* existing pod */, attachedVolumes); err != nil {
			return fwk.AsStatus(err)
		}
	}

	attachedVolumeCount := map[string]int{}
	for volumeUniqueName, driverName := range attachedVolumes {
		// Don't count single volume used in multiple pods more than once
		delete(newVolumes, volumeUniqueName)
		attachedVolumeCount[driverName]++
	}

	// Count CSI volumes from VolumeAttachments
	volumeAttachments, err := pl.getNodeVolumeAttachmentInfo(logger, node.Name)
	if err != nil {
		return fwk.AsStatus(err)
	}

	for volumeUniqueName, driverName := range volumeAttachments {
		// Avoid double-counting volumes already used by existing pods
		if _, exists := attachedVolumes[volumeUniqueName]; !exists {
			attachedVolumeCount[driverName]++
		}
	}

	// Count the new volumes count per driver
	newVolumeCount := map[string]int{}
	for _, driverName := range newVolumes {
		newVolumeCount[driverName]++
	}

	for driverName, count := range newVolumeCount {
		maxVolumeLimit, ok := nodeVolumeLimits[driverName]
		if ok {
			currentVolumeCount := attachedVolumeCount[driverName]
			logger.V(5).Info("Found plugin volume limits", "node", node.Name, "driverName", driverName,
				"maxLimits", maxVolumeLimit, "currentVolumeCount", currentVolumeCount, "newVolumeCount", count,
				"pod", klog.KObj(pod))
			if currentVolumeCount+count > int(maxVolumeLimit) {
				return fwk.NewStatus(fwk.Unschedulable, ErrReasonMaxVolumeCountExceeded)
			}
		}
	}

	return nil
}

func (pl *CSILimits) checkCSIDriverOnNode(pluginName string, csiNode *storagev1.CSINode) (bool, error) {
	// the registered driver must be a CSI driver to enforce this limit, if we can't find the driver,
	// we assume the driver may not be a CSI driver and allow the pod to be scheduled.
	_, err := pl.csiDriverLister.Get(pluginName)
	if err != nil {
		if apierrors.IsNotFound(err) {
			return true, nil
		}
		return false, fmt.Errorf("error getting CSIDriver for provider %s: %w", pluginName, err)
	}

	if csiNode == nil {
		return false, nil
	}

	for _, driver := range csiNode.Spec.Drivers {
		if driver.Name == pluginName {
			return true, nil
		}
	}
	return false, nil
}

// filterAttachableVolumes filters the attachable volumes from the pod and adds them to the result map.
// The result map is a map of volumeUniqueName to driver name. The volumeUniqueName is a unique name for
// the volume in the format of "driverName/volumeHandle". And driver name is the CSI driver name.
func (pl *CSILimits) filterAttachableVolumes(
	logger klog.Logger, pod *v1.Pod, csiNode *storagev1.CSINode, newPod bool, result map[string]string) error {
	for _, vol := range pod.Spec.Volumes {
		pvcName := ""
		isEphemeral := false
		switch {
		case vol.PersistentVolumeClaim != nil:
			// Normal CSI volume can only be used through PVC
			pvcName = vol.PersistentVolumeClaim.ClaimName
		case vol.Ephemeral != nil:
			// Generic ephemeral inline volumes also use a PVC,
			// just with a computed name and certain ownership.
			// That is checked below once the pvc object is
			// retrieved.
			pvcName = ephemeral.VolumeClaimName(pod, &vol)
			isEphemeral = true
		default:
			// Inline Volume does not have PVC.
			// Need to check if CSI migration is enabled for this inline volume.
			// - If the volume is migratable and CSI migration is enabled, need to count it
			// as well.
			// - If the volume is not migratable, it will be count in non_csi filter.
			if err := pl.checkAttachableInlineVolume(logger, &vol, csiNode, pod, result); err != nil {
				return err
			}

			continue
		}

		if pvcName == "" {
			return fmt.Errorf("PersistentVolumeClaim had no name")
		}

		pvc, err := pl.pvcLister.PersistentVolumeClaims(pod.Namespace).Get(pvcName)

		if err != nil {
			if newPod {
				// The PVC is required to proceed with
				// scheduling of a new pod because it cannot
				// run without it. Bail out immediately.
				return fmt.Errorf("looking up PVC %s/%s: %w", pod.Namespace, pvcName, err)
			}
			// If the PVC is invalid, we don't count the volume because
			// there's no guarantee that it belongs to the running predicate.
			logger.V(5).Info("Unable to look up PVC info", "pod", klog.KObj(pod), "PVC", klog.KRef(pod.Namespace, pvcName))
			continue
		}

		// The PVC for an ephemeral volume must be owned by the pod.
		if isEphemeral {
			if err := ephemeral.VolumeIsForPod(pod, pvc); err != nil {
				return err
			}
		}

		driverName, volumeHandle := pl.getCSIDriverInfo(logger, csiNode, pvc)
		if driverName == "" || volumeHandle == "" {
			logger.V(5).Info("Could not find a CSI driver name or volume handle, not counting volume")
			continue
		}

		volumeUniqueName := getVolumeUniqueName(driverName, volumeHandle)
		result[volumeUniqueName] = driverName
	}
	return nil
}

// checkAttachableInlineVolume takes an inline volume and add to the result map if the
// volume is migratable and CSI migration for this plugin has been enabled.
func (pl *CSILimits) checkAttachableInlineVolume(logger klog.Logger, vol *v1.Volume, csiNode *storagev1.CSINode,
	pod *v1.Pod, result map[string]string) error {
	if !pl.translator.IsInlineMigratable(vol) {
		return nil
	}
	// Check if the intree provisioner CSI migration has been enabled.
	inTreeProvisionerName, err := pl.translator.GetInTreePluginNameFromSpec(nil, vol)
	if err != nil {
		return fmt.Errorf("looking up provisioner name for volume %s: %w", vol.Name, err)
	}
	if !isCSIMigrationOn(csiNode, inTreeProvisionerName, pl.enableCSIMigrationPortworx) {
		csiNodeName := ""
		if csiNode != nil {
			csiNodeName = csiNode.Name
		}
		logger.V(5).Info("CSI Migration is not enabled for provisioner", "provisioner", inTreeProvisionerName,
			"pod", klog.KObj(pod), "csiNode", csiNodeName)
		return nil
	}
	// Do translation for the in-tree volume.
	translatedPV, err := pl.translator.TranslateInTreeInlineVolumeToCSI(logger, vol, pod.Namespace)
	if err != nil || translatedPV == nil {
		return fmt.Errorf("converting volume(%s) from inline to csi: %w", vol.Name, err)
	}
	driverName, err := pl.translator.GetCSINameFromInTreeName(inTreeProvisionerName)
	if err != nil {
		return fmt.Errorf("looking up CSI driver name for provisioner %s: %w", inTreeProvisionerName, err)
	}
	// TranslateInTreeInlineVolumeToCSI should translate inline volume to CSI. If it is not set,
	// the volume does not support inline. Skip the count.
	if translatedPV.Spec.PersistentVolumeSource.CSI == nil {
		return nil
	}
	volumeUniqueName := getVolumeUniqueName(driverName, translatedPV.Spec.PersistentVolumeSource.CSI.VolumeHandle)
	result[volumeUniqueName] = driverName
	return nil
}

// getCSIDriverInfo returns the CSI driver name and volume ID of a given PVC.
// If the PVC is from a migrated in-tree plugin, this function will return
// the information of the CSI driver that the plugin has been migrated to.
func (pl *CSILimits) getCSIDriverInfo(logger klog.Logger, csiNode *storagev1.CSINode, pvc *v1.PersistentVolumeClaim) (string, string) {
	pvName := pvc.Spec.VolumeName

	if pvName == "" {
		logger.V(5).Info("Persistent volume had no name for claim", "PVC", klog.KObj(pvc))
		return pl.getCSIDriverInfoFromSC(logger, csiNode, pvc)
	}

	pv, err := pl.pvLister.Get(pvName)
	if err != nil {
		logger.V(5).Info("Unable to look up PV info for PVC and PV", "PVC", klog.KObj(pvc), "PV", klog.KRef("", pvName))
		// If we can't fetch PV associated with PVC, may be it got deleted
		// or PVC was prebound to a PVC that hasn't been created yet.
		// fallback to using StorageClass for volume counting
		return pl.getCSIDriverInfoFromSC(logger, csiNode, pvc)
	}

	csiSource := pv.Spec.PersistentVolumeSource.CSI
	if csiSource == nil {
		// We make a fast path for non-CSI volumes that aren't migratable
		if !pl.translator.IsPVMigratable(pv) {
			return "", ""
		}

		pluginName, err := pl.translator.GetInTreePluginNameFromSpec(pv, nil)
		if err != nil {
			logger.V(5).Info("Unable to look up plugin name from PV spec", "err", err)
			return "", ""
		}

		if !isCSIMigrationOn(csiNode, pluginName, pl.enableCSIMigrationPortworx) {
			logger.V(5).Info("CSI Migration of plugin is not enabled", "plugin", pluginName)
			return "", ""
		}

		csiPV, err := pl.translator.TranslateInTreePVToCSI(logger, pv)
		if err != nil {
			logger.V(5).Info("Unable to translate in-tree volume to CSI", "err", err)
			return "", ""
		}

		if csiPV.Spec.PersistentVolumeSource.CSI == nil {
			logger.V(5).Info("Unable to get a valid volume source for translated PV", "PV", pvName)
			return "", ""
		}

		csiSource = csiPV.Spec.PersistentVolumeSource.CSI
	}

	return csiSource.Driver, csiSource.VolumeHandle
}

// getCSIDriverInfoFromSC returns the CSI driver name and a random volume ID of a given PVC's StorageClass.
func (pl *CSILimits) getCSIDriverInfoFromSC(logger klog.Logger, csiNode *storagev1.CSINode, pvc *v1.PersistentVolumeClaim) (string, string) {
	namespace := pvc.Namespace
	pvcName := pvc.Name
	scName := storagehelpers.GetPersistentVolumeClaimClass(pvc)

	// If StorageClass is not set or not found, then PVC must be using immediate binding mode
	// and hence it must be bound before scheduling. So it is safe to not count it.
	if scName == "" {
		logger.V(5).Info("PVC has no StorageClass", "PVC", klog.KObj(pvc))
		return "", ""
	}

	storageClass, err := pl.scLister.Get(scName)
	if err != nil {
		logger.V(5).Info("Could not get StorageClass for PVC", "PVC", klog.KObj(pvc), "err", err)
		return "", ""
	}

	// We use random prefix to avoid conflict with volume IDs. If PVC is bound during the execution of the
	// predicate and there is another pod on the same node that uses same volume, then we will overcount
	// the volume and consider both volumes as different.
	volumeHandle := fmt.Sprintf("%s-%s/%s", pl.randomVolumeIDPrefix, namespace, pvcName)

	provisioner := storageClass.Provisioner
	if pl.translator.IsMigratableIntreePluginByName(provisioner) {
		if !isCSIMigrationOn(csiNode, provisioner, pl.enableCSIMigrationPortworx) {
			logger.V(5).Info("CSI Migration of provisioner is not enabled", "provisioner", provisioner)
			return "", ""
		}

		driverName, err := pl.translator.GetCSINameFromInTreeName(provisioner)
		if err != nil {
			logger.V(5).Info("Unable to look up driver name from provisioner name", "provisioner", provisioner, "err", err)
			return "", ""
		}
		return driverName, volumeHandle
	}

	return provisioner, volumeHandle
}

// NewCSI initializes a new plugin and returns it.
func NewCSI(_ context.Context, _ runtime.Object, handle fwk.Handle, fts feature.Features) (fwk.Plugin, error) {
	informerFactory := handle.SharedInformerFactory()
	pvLister := informerFactory.Core().V1().PersistentVolumes().Lister()
	pvcLister := informerFactory.Core().V1().PersistentVolumeClaims().Lister()
	scLister := informerFactory.Storage().V1().StorageClasses().Lister()
	vaLister := informerFactory.Storage().V1().VolumeAttachments().Lister()
	csiDriverLister := informerFactory.Storage().V1().CSIDrivers().Lister()
	csiTranslator := csitrans.New()

	return &CSILimits{
		csiManager:                 handle.SharedCSIManager(),
		pvLister:                   pvLister,
		pvcLister:                  pvcLister,
		scLister:                   scLister,
		vaLister:                   vaLister,
		csiDriverLister:            csiDriverLister,
		enableCSIMigrationPortworx: fts.EnableCSIMigrationPortworx,
		enableVolumeLimitScaling:   fts.EnableVolumeLimitScaling,
		randomVolumeIDPrefix:       rand.String(32),
		translator:                 csiTranslator,
	}, nil
}

// getVolumeLimits reads the volume limits from CSINode object and returns a map of volume limits.
// The key is the driver name and the value is the maximum number of volumes that can be attached to the node.
// If a key is not found in the map, it means there is no limit for the driver on the node.
func getVolumeLimits(csiNode *storagev1.CSINode) map[string]int64 {
	nodeVolumeLimits := make(map[string]int64)
	if csiNode == nil {
		return nodeVolumeLimits
	}
	for _, d := range csiNode.Spec.Drivers {
		if d.Allocatable != nil && d.Allocatable.Count != nil {
			nodeVolumeLimits[d.Name] = int64(*d.Allocatable.Count)
		}
	}
	return nodeVolumeLimits
}

// getNodeVolumeAttachmentInfo returns a map of volumeID to driver name for the given node.
func (pl *CSILimits) getNodeVolumeAttachmentInfo(logger klog.Logger, nodeName string) (map[string]string, error) {
	volumeAttachments := make(map[string]string)
	vas, err := pl.vaLister.List(labels.Everything())
	if err != nil {
		return nil, err
	}
	for _, va := range vas {
		if va.Spec.NodeName == nodeName {
			if va.Spec.Attacher == "" {
				logger.V(5).Info("VolumeAttachment has no attacher", "VolumeAttachment", klog.KObj(va))
				continue
			}
			if va.Spec.Source.PersistentVolumeName == nil {
				logger.V(5).Info("VolumeAttachment has no PV name", "VolumeAttachment", klog.KObj(va))
				continue
			}
			pv, err := pl.pvLister.Get(*va.Spec.Source.PersistentVolumeName)
			if err != nil {
				logger.V(5).Info("Unable to get PV for VolumeAttachment", "VolumeAttachment", klog.KObj(va), "err", err)
				continue
			}
			if pv.Spec.CSI == nil {
				logger.V(5).Info("PV is not a CSI volume", "PV", klog.KObj(pv))
				continue
			}
			volumeID := getVolumeUniqueName(va.Spec.Attacher, pv.Spec.CSI.VolumeHandle)
			volumeAttachments[volumeID] = va.Spec.Attacher
		}
	}
	return volumeAttachments, nil
}

func getVolumeUniqueName(driverName, volumeHandle string) string {
	return fmt.Sprintf("%s/%s", driverName, volumeHandle)
}

// Feasibility and scoring based on the non-synthetic volume sources.
func (pl *CSILimits) SignPod(ctx context.Context, pod *v1.Pod) ([]fwk.SignFragment, *fwk.Status) {
	return []fwk.SignFragment{
		{Key: fwk.VolumesSignerName, Value: fwk.VolumesSigner(pod)},
	}, nil
}