per-volume ephemeral mode

This removes the limitation that the driver can only be deployed for
one mode or the other. Instead the driver uses the new
csi.storage.k8s.io/ephemeral
field (kubernetes/kubernetes#79624) in the
volume context to determine how it should behave in NodePublishVolume.

Supporting both modes in the same deployment makes it possible to test
ephemeral mode without having to change how the Prow jobs deploy the
driver, which is once as part of the cluster setup.

The --ephemeral parameter is still supported and can be used to force
the driver into ephemeral mode, which is useful when deploying on
Kubernetes 1.15 where csi.storage.k8s.io/ephemeral is not supported.

Author: pohly

README.md

@@ -346,7 +346,7 @@ Follow the following example to create a volume from a volume snapshot:
 As of version 1.15 of Kubernetes, the CSI Hostpath driver (starting with version 1.0.1) now includes support for inline ephemeral volume.  This means that a volume can be specified directly inside a pod spec without the need to use a persistent volume object.
 Find out how to enable or create a CSI inline driver [here](https://kubernetes-csi.github.io/docs/ephemeral-local-volumes.html)
 
-To test this feature, redeploy the CSI Hostpath plugin YAML by updating the `hostpath` container to use  the inline ephemeral mode by setting the `ephemeral` flag, of the driver binary, to true as shown in the following setup:
+To test this feature on Kubernetes 1.15, redeploy the CSI Hostpath plugin YAML by updating the `hostpath` container to use  the inline ephemeral mode by setting the `ephemeral` flag, of the driver binary, to true as shown in the following setup:
 
 ```yaml
 kind: DaemonSet
@@ -369,6 +369,9 @@ spec:
 
 ```
 Notice the addition of the `ephemeral=true` flag used in the `args:` block in the previous snippet.
+This is an intermediate solution for Kubernetes 1.15. Kubernetes 1.16 will provide [additional
+information to the driver](https://github.com/kubernetes/kubernetes/pull/79983) which makes it
+possible to use the normal deployment for both inline ephemeral volumes and persistent volumes.
 
 Once the driver plugin has been deployed, it can be tested by deploying a simple pod which has an inline volume specified in the spec:
 

cmd/hostpathplugin/main.go

@@ -33,7 +33,7 @@ var (
 	endpoint    = flag.String("endpoint", "unix://tmp/csi.sock", "CSI endpoint")
 	driverName  = flag.String("drivername", "hostpath.csi.k8s.io", "name of the driver")
 	nodeID      = flag.String("nodeid", "", "node id")
-	ephemeral   = flag.Bool("ephemeral", false, "deploy in ephemeral mode")
+	ephemeral   = flag.Bool("ephemeral", false, "publish volumes in ephemeral mode even if kubelet did not ask for it (only needed for Kubernetes 1.15)")
 	showVersion = flag.Bool("version", false, "Show version.")
 	// Set by the build process
 	version = ""

pkg/hostpath/controllerserver.go

@@ -167,7 +167,7 @@ func (cs *controllerServer) CreateVolume(ctx context.Context, req *csi.CreateVol
 		}
 	}
 
-	vol, err := createHostpathVolume(volumeID, req.GetName(), capacity, requestedAccessType)
+	vol, err := createHostpathVolume(volumeID, req.GetName(), capacity, requestedAccessType, false /* ephemeral */)
 	if err != nil {
 		return nil, status.Error(codes.Internal, fmt.Sprintf("failed to create volume: %s", err))
 	}

pkg/hostpath/hostpath.go

@@ -53,6 +53,7 @@ type hostPathVolume struct {
 	VolSize       int64      `json:"volSize"`
 	VolPath       string     `json:"volPath"`
 	VolAccessType accessType `json:"volAccessType"`
+	Ephemeral     bool       `json:"ephemeral"`
 }
 
 type hostPathSnapshot struct {
@@ -148,7 +149,7 @@ func getVolumePath(volID string) string {
 
 // createVolume create the directory for the hostpath volume.
 // It returns the volume path or err if one occurs.
-func createHostpathVolume(volID, name string, cap int64, volAccessType accessType) (*hostPathVolume, error) {
+func createHostpathVolume(volID, name string, cap int64, volAccessType accessType, ephemeral bool) (*hostPathVolume, error) {
 	path := getVolumePath(volID)
 	if volAccessType == mountAccess {
 		err := os.MkdirAll(path, 0777)
@@ -163,6 +164,7 @@ func createHostpathVolume(volID, name string, cap int64, volAccessType accessTyp
 		VolSize:       cap,
 		VolPath:       path,
 		VolAccessType: volAccessType,
+		Ephemeral:     ephemeral,
 	}
 	hostPathVolumes[volID] = hostpathVol
 	return &hostpathVol, nil

pkg/hostpath/nodeserver.go

@@ -57,17 +57,19 @@ func (ns *nodeServer) NodePublishVolume(ctx context.Context, req *csi.NodePublis
 	}
 
 	targetPath := req.GetTargetPath()
+	ephemeralVolume := req.GetVolumeContext()["csi.storage.k8s.io/ephemeral"] == "true" ||
+		req.GetVolumeContext()["csi.storage.k8s.io/ephemeral"] == "" && ns.ephemeral // Kubernetes 1.15 doesn't have csi.storage.k8s.io/ephemeral.
 
 	if req.GetVolumeCapability().GetBlock() != nil &&
 		req.GetVolumeCapability().GetMount() != nil {
 		return nil, status.Error(codes.InvalidArgument, "cannot have both block and mount access type")
 	}
 
 	// if ephemeral is specified, create volume here to avoid errors
-	if ns.ephemeral {
+	if ephemeralVolume {
 		volID := req.GetVolumeId()
 		volName := fmt.Sprintf("ephemeral-%s", volID)
-		vol, err := createHostpathVolume(req.GetVolumeId(), volName, maxStorageCapacity, mountAccess)
+		vol, err := createHostpathVolume(req.GetVolumeId(), volName, maxStorageCapacity, mountAccess, ephemeralVolume)
 		if err != nil && !os.IsExist(err) {
 			glog.Error("ephemeral mode failed to create volume: ", err)
 			return nil, status.Error(codes.Internal, err.Error())
@@ -170,7 +172,7 @@ func (ns *nodeServer) NodePublishVolume(ctx context.Context, req *csi.NodePublis
 		if err := mounter.Mount(path, targetPath, "", options); err != nil {
 			var errList strings.Builder
 			errList.WriteString(err.Error())
-			if ns.ephemeral {
+			if vol.Ephemeral {
 				if rmErr := os.RemoveAll(path); rmErr != nil && !os.IsNotExist(rmErr) {
 					errList.WriteString(fmt.Sprintf(" :%s", rmErr.Error()))
 				}
@@ -218,7 +220,7 @@ func (ns *nodeServer) NodeUnpublishVolume(ctx context.Context, req *csi.NodeUnpu
 		glog.V(4).Infof("hostpath: volume %s/%s has been unmounted.", targetPath, volumeID)
 	}
 
-	if ns.ephemeral {
+	if vol.Ephemeral {
 		glog.V(4).Infof("deleting volume %s", volumeID)
 		if err := deleteHostpathVolume(volumeID); err != nil && !os.IsNotExist(err) {
 			return nil, status.Error(codes.Internal, fmt.Sprintf("failed to delete volume: %s", err))