Merge pull request #47503 from chakri-nelluri/flexcap

Automatic merge from submit-queue (batch tested with PRs 47878, 47503, 47857)

Remove controller node plugin driver dependency for non-attachable fl…

…ex volume drivers (Ex: NFS).

**What this PR does / why we need it**:
Removes requirement to install flex volume drivers on master node for non-attachable drivers likes NFS.

**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*: fixes #47109


```release-note
Fixes issue w/Flex volume, introduced in 1.6.0, where drivers without an attacher would fail (node indefinitely waiting for attach). Drivers that don't implement attach should return `attach: false` on `init`.
```

examples/volumes/flexvolume/nfs

@@ -83,7 +83,7 @@ unmount() {
 op=$1
 
 if [ "$op" = "init" ]; then
-	log "{\"status\": \"Success\"}"
+	log "{\"status\": \"Success\", \"capabilities\": {\"attach\": false}}"
 	exit 0
 fi
 
@@ -100,9 +100,6 @@ case "$op" in
 	unmount)
 		unmount $*
 		;;
-	getvolumename)
-		getvolumename $*
-		;;
 	*)
 		log "{ \"status\": \"Not supported\" }"
 		exit 0

pkg/volume/flexvolume/attacher-defaults.go

@@ -17,8 +17,6 @@ limitations under the License.
 package flexvolume
 
 import (
-	"fmt"
-	"path"
 	"time"
 
 	"github.com/golang/glog"
@@ -33,30 +31,24 @@ type attacherDefaults flexVolumeAttacher
 
 // Attach is part of the volume.Attacher interface
 func (a *attacherDefaults) Attach(spec *volume.Spec, hostName types.NodeName) (string, error) {
-	glog.Warning(logPrefix(a.plugin), "using default Attach for volume ", spec.Name, ", host ", hostName)
+	glog.Warning(logPrefix(a.plugin.flexVolumePlugin), "using default Attach for volume ", spec.Name, ", host ", hostName)
 	return "", nil
 }
 
 // WaitForAttach is part of the volume.Attacher interface
 func (a *attacherDefaults) WaitForAttach(spec *volume.Spec, devicePath string, timeout time.Duration) (string, error) {
-	glog.Warning(logPrefix(a.plugin), "using default WaitForAttach for volume ", spec.Name, ", device ", devicePath)
+	glog.Warning(logPrefix(a.plugin.flexVolumePlugin), "using default WaitForAttach for volume ", spec.Name, ", device ", devicePath)
 	return devicePath, nil
 }
 
 // GetDeviceMountPath is part of the volume.Attacher interface
 func (a *attacherDefaults) GetDeviceMountPath(spec *volume.Spec, mountsDir string) (string, error) {
-	glog.Warning(logPrefix(a.plugin), "using default GetDeviceMountPath for volume ", spec.Name, ", mountsDir ", mountsDir)
-	volumeName, err := a.plugin.GetVolumeName(spec)
-	if err != nil {
-		return "", fmt.Errorf("GetVolumeName failed from GetDeviceMountPath: %s", err)
-	}
-
-	return path.Join(mountsDir, volumeName), nil
+	return a.plugin.getDeviceMountPath(spec)
 }
 
 // MountDevice is part of the volume.Attacher interface
 func (a *attacherDefaults) MountDevice(spec *volume.Spec, devicePath string, deviceMountPath string, mounter mount.Interface) error {
-	glog.Warning(logPrefix(a.plugin), "using default MountDevice for volume ", spec.Name, ", device ", devicePath, ", deviceMountPath ", deviceMountPath)
+	glog.Warning(logPrefix(a.plugin.flexVolumePlugin), "using default MountDevice for volume ", spec.Name, ", device ", devicePath, ", deviceMountPath ", deviceMountPath)
 	volSource, readOnly := getVolumeSource(spec)
 
 	options := make([]string, 0)

pkg/volume/flexvolume/attacher.go

@@ -17,7 +17,6 @@ limitations under the License.
 package flexvolume
 
 import (
-	"path"
 	"time"
 
 	"github.com/golang/glog"
@@ -26,7 +25,7 @@ import (
 )
 
 type flexVolumeAttacher struct {
-	plugin *flexVolumePlugin
+	plugin *flexVolumeAttachablePlugin
 }
 
 var _ volume.Attacher = &flexVolumeAttacher{}
@@ -64,9 +63,7 @@ func (a *flexVolumeAttacher) WaitForAttach(spec *volume.Spec, devicePath string,
 
 // GetDeviceMountPath is part of the volume.Attacher interface
 func (a *flexVolumeAttacher) GetDeviceMountPath(spec *volume.Spec) (string, error) {
-	mountsDir := path.Join(a.plugin.host.GetPluginDir(flexVolumePluginName), a.plugin.driverName, "mounts")
-
-	return (*attacherDefaults)(a).GetDeviceMountPath(spec, mountsDir)
+	return a.plugin.getDeviceMountPath(spec)
 }
 
 // MountDevice is part of the volume.Attacher interface

pkg/volume/flexvolume/common_test.go

@@ -28,16 +28,18 @@ import (
 	volumetesting "k8s.io/kubernetes/pkg/volume/testing"
 )
 
-func testPlugin() (*flexVolumePlugin, string) {
+func testPlugin() (*flexVolumeAttachablePlugin, string) {
 	rootDir, err := utiltesting.MkTmpdir("flexvolume_test")
 	if err != nil {
 		panic("error creating temp dir: " + err.Error())
 	}
-	return &flexVolumePlugin{
-		driverName:          "test",
-		execPath:            "/plugin",
-		host:                volumetesting.NewFakeVolumeHost(rootDir, nil, nil),
-		unsupportedCommands: []string{},
+	return &flexVolumeAttachablePlugin{
+		flexVolumePlugin: &flexVolumePlugin{
+			driverName:          "test",
+			execPath:            "/plugin",
+			host:                volumetesting.NewFakeVolumeHost(rootDir, nil, nil),
+			unsupportedCommands: []string{},
+		},
 	}, rootDir
 }
 
@@ -77,11 +79,11 @@ func fakeResultOutput(result interface{}) exec.FakeCombinedOutputAction {
 }
 
 func successOutput() exec.FakeCombinedOutputAction {
-	return fakeResultOutput(&DriverStatus{StatusSuccess, "", "", "", true})
+	return fakeResultOutput(&DriverStatus{StatusSuccess, "", "", "", true, nil})
 }
 
 func notSupportedOutput() exec.FakeCombinedOutputAction {
-	return fakeResultOutput(&DriverStatus{StatusNotSupported, "", "", "", false})
+	return fakeResultOutput(&DriverStatus{StatusNotSupported, "", "", "", false, nil})
 }
 
 func sameArgs(args, expectedArgs []string) bool {
@@ -126,7 +128,7 @@ func fakePersistentVolumeSpec() *volume.Spec {
 	return volume.NewSpecFromPersistentVolume(vol, false)
 }
 
-func specJson(plugin *flexVolumePlugin, spec *volume.Spec, extraOptions map[string]string) string {
+func specJson(plugin *flexVolumeAttachablePlugin, spec *volume.Spec, extraOptions map[string]string) string {
 	o, err := NewOptionsForDriver(spec, plugin.host, extraOptions)
 	if err != nil {
 		panic("Failed to convert spec: " + err.Error())

pkg/volume/flexvolume/detacher-defaults.go

@@ -28,18 +28,18 @@ type detacherDefaults flexVolumeDetacher
 
 // Detach is part of the volume.Detacher interface.
 func (d *detacherDefaults) Detach(deviceName string, hostName types.NodeName) error {
-	glog.Warning(logPrefix(d.plugin), "using default Detach for device ", deviceName, ", host ", hostName)
+	glog.Warning(logPrefix(d.plugin.flexVolumePlugin), "using default Detach for device ", deviceName, ", host ", hostName)
 	return nil
 }
 
 // WaitForDetach is part of the volume.Detacher interface.
 func (d *detacherDefaults) WaitForDetach(devicePath string, timeout time.Duration) error {
-	glog.Warning(logPrefix(d.plugin), "using default WaitForDetach for device ", devicePath)
+	glog.Warning(logPrefix(d.plugin.flexVolumePlugin), "using default WaitForDetach for device ", devicePath)
 	return nil
 }
 
 // UnmountDevice is part of the volume.Detacher interface.
 func (d *detacherDefaults) UnmountDevice(deviceMountPath string) error {
-	glog.Warning(logPrefix(d.plugin), "using default UnmountDevice for device mount path ", deviceMountPath)
+	glog.Warning(logPrefix(d.plugin.flexVolumePlugin), "using default UnmountDevice for device mount path ", deviceMountPath)
 	return util.UnmountPath(deviceMountPath, d.plugin.host.GetMounter())
 }

pkg/volume/flexvolume/detacher.go

@@ -28,7 +28,7 @@ import (
 )
 
 type flexVolumeDetacher struct {
-	plugin *flexVolumePlugin
+	plugin *flexVolumeAttachablePlugin
 }
 
 var _ volume.Detacher = &flexVolumeDetacher{}

pkg/volume/flexvolume/driver-call.go

@@ -58,6 +58,8 @@ const (
 	optionKeyPodUID       = "kubernetes.io/pod.uid"
 
 	optionKeyServiceAccountName = "kubernetes.io/serviceAccount.name"
+
+	attachCapability = "attach"
 )
 
 const (
@@ -199,6 +201,10 @@ type DriverStatus struct {
 	VolumeName string `json:"volumeName,omitempty"`
 	// Represents volume is attached on the node
 	Attached bool `json:"attached,omitempty"`
+	// Returns capabilities of the driver.
+	// By default we assume all the capabilities are supported.
+	// If the plugin does not support a capability, it can return false for that capability.
+	Capabilities map[string]bool
 }
 
 // isCmdNotSupportedErr checks if the error corresponds to command not supported by

pkg/volume/flexvolume/mounter-defaults.go

@@ -17,8 +17,6 @@ limitations under the License.
 package flexvolume
 
 import (
-	"fmt"
-
 	"github.com/golang/glog"
 
 	"k8s.io/kubernetes/pkg/volume"
@@ -31,13 +29,9 @@ type mounterDefaults flexVolumeMounter
 func (f *mounterDefaults) SetUpAt(dir string, fsGroup *int64) error {
 	glog.Warning(logPrefix(f.plugin), "using default SetUpAt to ", dir)
 
-	a, err := f.plugin.NewAttacher()
+	src, err := f.plugin.getDeviceMountPath(f.spec)
 	if err != nil {
-		return fmt.Errorf("NewAttacher failed: %v", err)
-	}
-	src, err := a.GetDeviceMountPath(f.spec)
-	if err != nil {
-		return fmt.Errorf("GetDeviceMountPath failed: %v", err)
+		return err
 	}
 
 	if err := doMount(f.mounter, src, dir, "auto", []string{"bind"}); err != nil {

pkg/volume/flexvolume/plugin.go

@@ -17,6 +17,7 @@ limitations under the License.
 package flexvolume
 
 import (
+	"fmt"
 	"path"
 	"strings"
 	"sync"
@@ -27,6 +28,7 @@ import (
 	api "k8s.io/kubernetes/pkg/api/v1"
 	"k8s.io/kubernetes/pkg/util/exec"
 	"k8s.io/kubernetes/pkg/util/mount"
+	utilstrings "k8s.io/kubernetes/pkg/util/strings"
 	"k8s.io/kubernetes/pkg/volume"
 )
 
@@ -43,9 +45,56 @@ type flexVolumePlugin struct {
 	unsupportedCommands []string
 }
 
-var _ volume.AttachableVolumePlugin = &flexVolumePlugin{}
+type flexVolumeAttachablePlugin struct {
+	*flexVolumePlugin
+}
+
+var _ volume.AttachableVolumePlugin = &flexVolumeAttachablePlugin{}
 var _ volume.PersistentVolumePlugin = &flexVolumePlugin{}
 
+func NewFlexVolumePlugin(pluginDir, name string) (volume.VolumePlugin, error) {
+	execPath := path.Join(pluginDir, name)
+
+	driverName := utilstrings.UnescapePluginName(name)
+
+	flexPlugin := &flexVolumePlugin{
+		driverName:          driverName,
+		execPath:            execPath,
+		runner:              exec.New(),
+		unsupportedCommands: []string{},
+	}
+
+	// Check whether the plugin is attachable.
+	ok, err := isAttachable(flexPlugin)
+	if err != nil {
+		return nil, err
+	}
+
+	if ok {
+		// Plugin supports attach/detach, so return flexVolumeAttachablePlugin
+		return &flexVolumeAttachablePlugin{flexVolumePlugin: flexPlugin}, nil
+	} else {
+		return flexPlugin, nil
+	}
+}
+
+func isAttachable(plugin *flexVolumePlugin) (bool, error) {
+	call := plugin.NewDriverCall(initCmd)
+	res, err := call.Run()
+	if err != nil {
+		return false, err
+	}
+
+	// By default all plugins are attachable, unless they report otherwise.
+	cap, ok := res.Capabilities[attachCapability]
+	if ok {
+		// cap is false, so plugin does not support attach/detach calls.
+		return cap, nil
+	}
+
+	return true, nil
+}
+
 // Init is part of the volume.VolumePlugin interface.
 func (plugin *flexVolumePlugin) Init(host volume.VolumeHost) error {
 	plugin.host = host
@@ -155,12 +204,12 @@ func (plugin *flexVolumePlugin) newUnmounterInternal(volName string, podUID type
 }
 
 // NewAttacher is part of the volume.AttachableVolumePlugin interface.
-func (plugin *flexVolumePlugin) NewAttacher() (volume.Attacher, error) {
+func (plugin *flexVolumeAttachablePlugin) NewAttacher() (volume.Attacher, error) {
 	return &flexVolumeAttacher{plugin}, nil
 }
 
 // NewDetacher is part of the volume.AttachableVolumePlugin interface.
-func (plugin *flexVolumePlugin) NewDetacher() (volume.Detacher, error) {
+func (plugin *flexVolumeAttachablePlugin) NewDetacher() (volume.Detacher, error) {
 	return &flexVolumeDetacher{plugin}, nil
 }
 
@@ -208,3 +257,13 @@ func (plugin *flexVolumePlugin) GetDeviceMountRefs(deviceMountPath string) ([]st
 	mounter := plugin.host.GetMounter()
 	return mount.GetMountRefs(mounter, deviceMountPath)
 }
+
+func (plugin *flexVolumePlugin) getDeviceMountPath(spec *volume.Spec) (string, error) {
+	volumeName, err := plugin.GetVolumeName(spec)
+	if err != nil {
+		return "", fmt.Errorf("GetVolumeName failed from getDeviceMountPath: %s", err)
+	}
+
+	mountsDir := path.Join(plugin.host.GetPluginDir(flexVolumePluginName), plugin.driverName, "mounts")
+	return path.Join(mountsDir, volumeName), nil
+}

pkg/volume/flexvolume/probe.go

@@ -18,10 +18,7 @@ package flexvolume
 
 import (
 	"io/ioutil"
-	"path"
 
-	"k8s.io/kubernetes/pkg/util/exec"
-	utilstrings "k8s.io/kubernetes/pkg/util/strings"
 	"k8s.io/kubernetes/pkg/volume"
 )
 
@@ -37,13 +34,12 @@ func ProbeVolumePlugins(pluginDir string) []volume.VolumePlugin {
 		// e.g. dirname = vendor~cifs
 		// then, executable will be pluginDir/dirname/cifs
 		if f.IsDir() {
-			execPath := path.Join(pluginDir, f.Name())
-			plugins = append(plugins, &flexVolumePlugin{
-				driverName:          utilstrings.UnescapePluginName(f.Name()),
-				execPath:            execPath,
-				runner:              exec.New(),
-				unsupportedCommands: []string{},
-			})
+			plugin, err := NewFlexVolumePlugin(pluginDir, f.Name())
+			if err != nil {
+				continue
+			}
+
+			plugins = append(plugins, plugin)
 		}
 	}
 	return plugins