Merge pull request #458 from harche/without_devices

virtcontainers: Add support for ephemeral volumes

cli/create.go

@@ -109,7 +109,6 @@ func create(containerID, bundlePath, console, pidFilePath string, detach bool,
 	disableOutput := noNeedForOutput(detach, ociSpec.Process.Terminal)
 
 	var process vc.Process
-
 	switch containerType {
 	case vc.PodSandbox:
 		process, err = createSandbox(ociSpec, runtimeConfig, containerID, bundlePath, console, disableOutput)
@@ -255,9 +254,25 @@ func createSandbox(ociSpec oci.CompatOCISpec, runtimeConfig oci.RuntimeConfig,
 	return containers[0].Process(), nil
 }
 
+// setEphemeralStorageType sets the mount type to 'ephemeral'
+// if the mount source path is provisioned by k8s for ephemeral storage.
+// For the given pod ephemeral volume is created only once
+// backed by tmpfs inside the VM. For successive containers
+// of the same pod the already existing volume is reused.
+func setEphemeralStorageType(ociSpec oci.CompatOCISpec) oci.CompatOCISpec {
+	for idx, mnt := range ociSpec.Mounts {
+		if IsEphemeralStorage(mnt.Source) {
+			ociSpec.Mounts[idx].Type = "ephemeral"
+		}
+	}
+	return ociSpec
+}
+
 func createContainer(ociSpec oci.CompatOCISpec, containerID, bundlePath,
 	console string, disableOutput bool) (vc.Process, error) {
 
+	ociSpec = setEphemeralStorageType(ociSpec)
+
 	contConfig, err := oci.ContainerConfig(ociSpec, bundlePath, containerID, console, disableOutput)
 	if err != nil {
 		return vc.Process{}, err

cli/create_test.go

@@ -1010,6 +1010,24 @@ func TestCreateCreateContainerFail(t *testing.T) {
 	}
 }
 
+func TestSetEphemeralStorageType(t *testing.T) {
+	assert := assert.New(t)
+
+	ociSpec := oci.CompatOCISpec{}
+	var ociMounts []specs.Mount
+	mount := specs.Mount{
+		Source: "/var/lib/kubelet/pods/366c3a77-4869-11e8-b479-507b9ddd5ce4/volumes/kubernetes.io~empty-dir/cache-volume",
+	}
+
+	ociMounts = append(ociMounts, mount)
+	ociSpec.Mounts = ociMounts
+	ociSpec = setEphemeralStorageType(ociSpec)
+
+	mountType := ociSpec.Mounts[0].Type
+	assert.Equal(mountType, "ephemeral",
+		"Unexpected mount type, got %s expected ephemeral", mountType)
+}
+
 func TestCreateCreateContainer(t *testing.T) {
 	assert := assert.New(t)
 

cli/utils.go

@@ -15,7 +15,10 @@ import (
 	"strings"
 )
 
-const unknown = "<<unknown>>"
+const (
+	unknown     = "<<unknown>>"
+	k8sEmptyDir = "kubernetes.io~empty-dir"
+)
 
 // variables to allow tests to modify the values
 var (
@@ -43,6 +46,26 @@ func getFileContents(file string) (string, error) {
 	return string(bytes), nil
 }
 
+// IsEphemeralStorage returns true if the given path
+// to the storage belongs to kubernetes ephemeral storage
+//
+// This method depends on a specific path used by k8s
+// to detect if it's of type ephemeral. As of now,
+// this is a very k8s specific solution that works
+// but in future there should be a better way for this
+// method to determine if the path is for ephemeral
+// volume type
+func IsEphemeralStorage(path string) bool {
+	splitSourceSlice := strings.Split(path, "/")
+	if len(splitSourceSlice) > 1 {
+		storageType := splitSourceSlice[len(splitSourceSlice)-2]
+		if storageType == k8sEmptyDir {
+			return true
+		}
+	}
+	return false
+}
+
 func getKernelVersion() (string, error) {
 	contents, err := getFileContents(procVersion)
 	if err != nil {

cli/utils_test.go

@@ -38,6 +38,20 @@ func TestFileExists(t *testing.T) {
 		fmt.Sprintf("File %q should exist", file))
 }
 
+func TestIsEphemeralStorage(t *testing.T) {
+	sampleEphePath := "/var/lib/kubelet/pods/366c3a75-4869-11e8-b479-507b9ddd5ce4/volumes/kubernetes.io~empty-dir/cache-volume"
+	isEphe := IsEphemeralStorage(sampleEphePath)
+	if !isEphe {
+		t.Fatalf("Unable to correctly determine volume type")
+	}
+
+	sampleEphePath = "/var/lib/kubelet/pods/366c3a75-4869-11e8-b479-507b9ddd5ce4/volumes/cache-volume"
+	isEphe = IsEphemeralStorage(sampleEphePath)
+	if isEphe {
+		t.Fatalf("Unable to correctly determine volume type")
+	}
+}
+
 func TestGetFileContents(t *testing.T) {
 	type testData struct {
 		contents string

virtcontainers/kata_agent.go

@@ -52,6 +52,7 @@ var (
 	sharedDir9pOptions    = []string{"trans=virtio,version=9p2000.L", "nodev"}
 	shmDir                = "shm"
 	kataEphemeralDevType  = "ephemeral"
+	ephemeralPath         = filepath.Join(kataGuestSandboxDir, kataEphemeralDevType)
 )
 
 // KataAgentConfig is a structure storing information needed
@@ -803,6 +804,9 @@ func (k *kataAgent) createContainer(sandbox *Sandbox, c *Container) (p *Process,
 		return nil, err
 	}
 
+	epheStorages := k.handleEphemeralStorage(ociSpec.Mounts)
+	ctrStorages = append(ctrStorages, epheStorages...)
+
 	// We replace all OCI mount sources that match our container mount
 	// with the right source path (The guest one).
 	if err = k.replaceOCIMountSource(ociSpec, newMounts); err != nil {
@@ -868,6 +872,29 @@ func (k *kataAgent) createContainer(sandbox *Sandbox, c *Container) (p *Process,
 		k.state.URL, c.config.Cmd, createNSList, enterNSList)
 }
 
+// handleEphemeralStorage handles ephemeral storages by
+// creating a Storage from corresponding source of the mount point
+func (k *kataAgent) handleEphemeralStorage(mounts []specs.Mount) []*grpc.Storage {
+	var epheStorages []*grpc.Storage
+	for idx, mnt := range mounts {
+		if mnt.Type == kataEphemeralDevType {
+			// Set the mount source path to a path that resides inside the VM
+			mounts[idx].Source = filepath.Join(ephemeralPath, filepath.Base(mnt.Source))
+
+			// Create a storage struct so that kata agent is able to create
+			// tmpfs backed volume inside the VM
+			epheStorage := &grpc.Storage{
+				Driver:     kataEphemeralDevType,
+				Source:     "tmpfs",
+				Fstype:     "tmpfs",
+				MountPoint: mounts[idx].Source,
+			}
+			epheStorages = append(epheStorages, epheStorage)
+		}
+	}
+	return epheStorages
+}
+
 // handleBlockVolumes handles volumes that are block devices files
 // by passing the block devices as Storage to the agent.
 func (k *kataAgent) handleBlockVolumes(c *Container) []*grpc.Storage {

virtcontainers/kata_agent_test.go

@@ -369,6 +369,25 @@ func TestGenerateInterfacesAndRoutes(t *testing.T) {
 
 }
 
+func TestHandleEphemeralStorage(t *testing.T) {
+	k := kataAgent{}
+	var ociMounts []specs.Mount
+	mountSource := "/tmp/mountPoint"
+
+	mount := specs.Mount{
+		Type:   kataEphemeralDevType,
+		Source: mountSource,
+	}
+
+	ociMounts = append(ociMounts, mount)
+	epheStorages := k.handleEphemeralStorage(ociMounts)
+
+	epheMountPoint := epheStorages[0].GetMountPoint()
+	expected := filepath.Join(ephemeralPath, filepath.Base(mountSource))
+	assert.Equal(t, epheMountPoint, expected,
+		"Ephemeral mount point didn't match: got %s, expecting %s", epheMountPoint, expected)
+}
+
 func TestAppendDevicesEmptyContainerDeviceList(t *testing.T) {
 	k := kataAgent{}