Add ImageFsInfo support

Signed-off-by: Lantao Liu <lantaol@google.com>

cmd/cri-containerd/options/options.go

@@ -31,6 +31,8 @@ const configFilePathArgName = "config"
 
 // ContainerdConfig contains config related to containerd
 type ContainerdConfig struct {
+	// ContainerdRootDir is the root directory path for containerd.
+	ContainerdRootDir string `toml:"root"`
 	// ContainerdSnapshotter is the snapshotter used by containerd.
 	ContainerdSnapshotter string `toml:"snapshotter"`
 	// ContainerdEndpoint is the containerd endpoint path.
@@ -66,6 +68,8 @@ type Config struct {
 	EnableSelinux bool `toml:"enable_selinux"`
 	// SandboxImage is the image used by sandbox container.
 	SandboxImage string `toml:"sandbox_image"`
+	// StatsCollectPeriod is the period (in seconds) of snapshots stats collection.
+	StatsCollectPeriod int `toml:"stats_collect_period"`
 }
 
 // CRIContainerdOptions contains cri-containerd command line and toml options.
@@ -93,6 +97,9 @@ func (c *CRIContainerdOptions) AddFlags(fs *pflag.FlagSet) {
 		"/var/run/cri-containerd.sock", "Path to the socket which cri-containerd serves on.")
 	fs.StringVar(&c.RootDir, "root-dir",
 		"/var/lib/cri-containerd", "Root directory path for cri-containerd managed files (metadata checkpoint etc).")
+	fs.StringVar(&c.ContainerdRootDir, "containerd-root-dir",
+		"/var/lib/containerd", "Root directory path where containerd stores persistent data. "+
+			"This should be the same with containerd `root`.")
 	fs.StringVar(&c.ContainerdEndpoint, "containerd-endpoint",
 		"/run/containerd/containerd.sock", "Path to the containerd endpoint.")
 	fs.StringVar(&c.ContainerdSnapshotter, "containerd-snapshotter",
@@ -113,6 +120,8 @@ func (c *CRIContainerdOptions) AddFlags(fs *pflag.FlagSet) {
 		false, "Enable selinux support.")
 	fs.StringVar(&c.SandboxImage, "sandbox-image",
 		"gcr.io/google_containers/pause:3.0", "The image used by sandbox container.")
+	fs.IntVar(&c.StatsCollectPeriod, "stats-collect-period",
+		10, "The period (in seconds) of snapshots stats collection.")
 	fs.BoolVar(&c.PrintDefaultConfig, "default-config",
 		false, "Print default toml config of cri-containerd and quit.")
 }

pkg/os/os.go

@@ -17,11 +17,13 @@ limitations under the License.
 package os
 
 import (
+	"fmt"
 	"io"
 	"io/ioutil"
 	"os"
 	"path/filepath"
 
+	containerdmount "github.com/containerd/containerd/mount"
 	"github.com/containerd/fifo"
 	"github.com/docker/docker/pkg/mount"
 	"golang.org/x/net/context"
@@ -41,6 +43,8 @@ type OS interface {
 	Mount(source string, target string, fstype string, flags uintptr, data string) error
 	Unmount(target string, flags int) error
 	GetMounts() ([]*mount.Info, error)
+	LookupMount(path string) (containerdmount.Info, error)
+	DeviceUUID(device string) (string, error)
 }
 
 // RealOS is used to dispatch the real system level operations.
@@ -120,3 +124,36 @@ func (RealOS) Unmount(target string, flags int) error {
 func (RealOS) GetMounts() ([]*mount.Info, error) {
 	return mount.GetMounts()
 }
+
+// LookupMount gets mount info of a given path.
+func (RealOS) LookupMount(path string) (containerdmount.Info, error) {
+	return containerdmount.Lookup(path)
+}
+
+// DeviceUUID gets device uuid of a device. The passed in device should be
+// an absolute path of the device.
+func (RealOS) DeviceUUID(device string) (string, error) {
+	const uuidDir = "/dev/disk/by-uuid"
+	if _, err := os.Stat(uuidDir); err != nil {
+		return "", err
+	}
+	files, err := ioutil.ReadDir(uuidDir)
+	if err != nil {
+		return "", err
+	}
+	for _, file := range files {
+		path := filepath.Join(uuidDir, file.Name())
+		target, err := os.Readlink(path)
+		if err != nil {
+			return "", err
+		}
+		dev, err := filepath.Abs(filepath.Join(uuidDir, target))
+		if err != nil {
+			return "", err
+		}
+		if dev == device {
+			return file.Name(), nil
+		}
+	}
+	return "", fmt.Errorf("device not found")
+}

pkg/os/testing/fake_os.go

@@ -21,6 +21,7 @@ import (
 	"os"
 	"sync"
 
+	containerdmount "github.com/containerd/containerd/mount"
 	"github.com/docker/docker/pkg/mount"
 	"golang.org/x/net/context"
 
@@ -50,6 +51,8 @@ type FakeOS struct {
 	MountFn               func(source string, target string, fstype string, flags uintptr, data string) error
 	UnmountFn             func(target string, flags int) error
 	GetMountsFn           func() ([]*mount.Info, error)
+	LookupMountFn         func(path string) (containerdmount.Info, error)
+	DeviceUUIDFn          func(device string) (string, error)
 	calls                 []CalledDetail
 	errors                map[string]error
 }
@@ -240,3 +243,29 @@ func (f *FakeOS) GetMounts() ([]*mount.Info, error) {
 	}
 	return nil, nil
 }
+
+// LookupMount is a fake call that invokes LookupMountFn or just return nil.
+func (f *FakeOS) LookupMount(path string) (containerdmount.Info, error) {
+	f.appendCalls("LookupMount", path)
+	if err := f.getError("LookupMount"); err != nil {
+		return containerdmount.Info{}, err
+	}
+
+	if f.LookupMountFn != nil {
+		return f.LookupMountFn(path)
+	}
+	return containerdmount.Info{}, nil
+}
+
+// DeviceUUID is a fake call that invodes DeviceUUIDFn or just return nil.
+func (f *FakeOS) DeviceUUID(device string) (string, error) {
+	f.appendCalls("DeviceUUID", device)
+	if err := f.getError("DeviceUUID"); err != nil {
+		return "", err
+	}
+
+	if f.DeviceUUIDFn != nil {
+		return f.DeviceUUIDFn(device)
+	}
+	return "", nil
+}

pkg/server/imagefs_info.go

@@ -17,7 +17,7 @@ limitations under the License.
 package server
 
 import (
-	"errors"
+	"time"
 
 	"golang.org/x/net/context"
 
@@ -26,5 +26,26 @@ import (
 
 // ImageFsInfo returns information of the filesystem that is used to store images.
 func (c *criContainerdService) ImageFsInfo(ctx context.Context, r *runtime.ImageFsInfoRequest) (*runtime.ImageFsInfoResponse, error) {
-	return nil, errors.New("not implemented")
+	snapshots := c.snapshotStore.List()
+	timestamp := time.Now().UnixNano()
+	var usedBytes, inodesUsed uint64
+	for _, sn := range snapshots {
+		// Use the oldest timestamp as the timestamp of imagefs info.
+		if sn.Timestamp < timestamp {
+			timestamp = sn.Timestamp
+		}
+		usedBytes += sn.Size
+		inodesUsed += sn.Inodes
+	}
+	// TODO(random-liu): Handle content store
+	return &runtime.ImageFsInfoResponse{
+		ImageFilesystems: []*runtime.FilesystemUsage{
+			{
+				Timestamp:  timestamp,
+				StorageId:  &runtime.StorageIdentifier{Uuid: c.imageFSUUID},
+				UsedBytes:  &runtime.UInt64Value{Value: usedBytes},
+				InodesUsed: &runtime.UInt64Value{Value: inodesUsed},
+			},
+		},
+	}, nil
 }

pkg/server/imagefs_info_test.go

@@ -0,0 +1,70 @@
+/*
+Copyright 2017 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 server
+
+import (
+	"testing"
+
+	"github.com/containerd/containerd/snapshot"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"golang.org/x/net/context"
+	"k8s.io/kubernetes/pkg/kubelet/apis/cri/v1alpha1/runtime"
+
+	snapshotstore "github.com/kubernetes-incubator/cri-containerd/pkg/store/snapshot"
+)
+
+func TestImageFsInfo(t *testing.T) {
+	c := newTestCRIContainerdService()
+	snapshots := []snapshotstore.Snapshot{
+		{
+			Key:       "key1",
+			Kind:      snapshot.KindActive,
+			Size:      10,
+			Inodes:    100,
+			Timestamp: 234567,
+		},
+		{
+			Key:       "key2",
+			Kind:      snapshot.KindCommitted,
+			Size:      20,
+			Inodes:    200,
+			Timestamp: 123456,
+		},
+		{
+			Key:       "key3",
+			Kind:      snapshot.KindView,
+			Size:      0,
+			Inodes:    0,
+			Timestamp: 345678,
+		},
+	}
+	expected := &runtime.FilesystemUsage{
+		Timestamp:  123456,
+		StorageId:  &runtime.StorageIdentifier{Uuid: testImageFSUUID},
+		UsedBytes:  &runtime.UInt64Value{Value: 30},
+		InodesUsed: &runtime.UInt64Value{Value: 300},
+	}
+	for _, sn := range snapshots {
+		c.snapshotStore.Add(sn)
+	}
+	resp, err := c.ImageFsInfo(context.Background(), &runtime.ImageFsInfoRequest{})
+	require.NoError(t, err)
+	stats := resp.GetImageFilesystems()
+	assert.Len(t, stats, 1)
+	assert.Equal(t, expected, stats[0])
+}

pkg/server/instrumented_service.go

@@ -280,3 +280,14 @@ func (in *instrumentedService) RemoveImage(ctx context.Context, r *runtime.Remov
 	}()
 	return in.criContainerdService.RemoveImage(ctx, r)
 }
+func (in *instrumentedService) ImageFsInfo(ctx context.Context, r *runtime.ImageFsInfoRequest) (res *runtime.ImageFsInfoResponse, err error) {
+	glog.V(4).Infof("ImageFsInfo")
+	defer func() {
+		if err != nil {
+			glog.Errorf("ImageFsInfo failed, error: %v", err)
+		} else {
+			glog.V(4).Infof("ImageFsInfo returns filesystem info %+v", res.ImageFilesystems)
+		}
+	}()
+	return in.criContainerdService.ImageFsInfo(ctx, r)
+}

pkg/server/service.go

@@ -20,12 +20,15 @@ import (
 	"fmt"
 	"net"
 	"os"
+	"path/filepath"
 	"syscall"
+	"time"
 
 	"github.com/containerd/containerd"
 	"github.com/containerd/containerd/api/services/tasks/v1"
 	"github.com/containerd/containerd/content"
 	"github.com/containerd/containerd/images"
+	"github.com/containerd/containerd/plugin"
 	"github.com/cri-o/ocicni/pkg/ocicni"
 	"github.com/golang/glog"
 	"golang.org/x/net/context"
@@ -39,6 +42,7 @@ import (
 	containerstore "github.com/kubernetes-incubator/cri-containerd/pkg/store/container"
 	imagestore "github.com/kubernetes-incubator/cri-containerd/pkg/store/image"
 	sandboxstore "github.com/kubernetes-incubator/cri-containerd/pkg/store/sandbox"
+	snapshotstore "github.com/kubernetes-incubator/cri-containerd/pkg/store/snapshot"
 )
 
 const (
@@ -60,6 +64,8 @@ type CRIContainerdService interface {
 type criContainerdService struct {
 	// config contains all configurations.
 	config options.Config
+	// imageFSUUID is the device uuid of image filesystem.
+	imageFSUUID string
 	// server is the grpc server.
 	server *grpc.Server
 	// os is an interface for all required os operations.
@@ -76,6 +82,8 @@ type criContainerdService struct {
 	containerNameIndex *registrar.Registrar
 	// imageStore stores all resources associated with images.
 	imageStore *imagestore.Store
+	// snapshotStore stores information of all snapshots.
+	snapshotStore *snapshotstore.Store
 	// taskService is containerd tasks client.
 	taskService tasks.TasksClient
 	// contentStoreService is the containerd content service client.
@@ -113,6 +121,7 @@ func NewCRIContainerdService(config options.Config) (CRIContainerdService, error
 		sandboxStore:        sandboxstore.NewStore(),
 		containerStore:      containerstore.NewStore(),
 		imageStore:          imagestore.NewStore(),
+		snapshotStore:       snapshotstore.NewStore(),
 		sandboxNameIndex:    registrar.NewRegistrar(),
 		containerNameIndex:  registrar.NewRegistrar(),
 		taskService:         client.TaskService(),
@@ -121,11 +130,16 @@ func NewCRIContainerdService(config options.Config) (CRIContainerdService, error
 		client:              client,
 	}
 
-	netPlugin, err := ocicni.InitCNI(config.NetworkPluginConfDir, config.NetworkPluginBinDir)
+	imageFSPath := imageFSPath(config.ContainerdRootDir, config.ContainerdSnapshotter)
+	c.imageFSUUID, err = c.getDeviceUUID(imageFSPath)
+	if err != nil {
+		return nil, fmt.Errorf("failed to get imagefs uuid: %v", err)
+	}
+
+	c.netPlugin, err = ocicni.InitCNI(config.NetworkPluginConfDir, config.NetworkPluginBinDir)
 	if err != nil {
 		return nil, fmt.Errorf("failed to initialize cni plugin: %v", err)
 	}
-	c.netPlugin = netPlugin
 
 	// prepare streaming server
 	c.streamServer, err = newStreamServer(c, config.StreamServerAddress, config.StreamServerPort)
@@ -156,6 +170,15 @@ func (c *criContainerdService) Run() error {
 	glog.V(2).Info("Start event monitor")
 	eventMonitorCloseCh := c.eventMonitor.start()
 
+	// Start snapshot stats syncer, it doesn't need to be stopped.
+	glog.V(2).Info("Start snapshots syncer")
+	snapshotsSyncer := newSnapshotsSyncer(
+		c.snapshotStore,
+		c.client.SnapshotService(c.config.ContainerdSnapshotter),
+		time.Duration(c.config.StatsCollectPeriod)*time.Second,
+	)
+	snapshotsSyncer.start()
+
 	// Start streaming server.
 	glog.V(2).Info("Start streaming server")
 	streamServerCloseCh := make(chan struct{})
@@ -209,3 +232,18 @@ func (c *criContainerdService) Stop() {
 	c.streamServer.Stop() // nolint: errcheck
 	c.server.Stop()
 }
+
+// getDeviceUUID gets device uuid for a given path.
+func (c *criContainerdService) getDeviceUUID(path string) (string, error) {
+	info, err := c.os.LookupMount(path)
+	if err != nil {
+		return "", err
+	}
+	return c.os.DeviceUUID(info.Source)
+}
+
+// imageFSPath returns containerd image filesystem path.
+// Note that if containerd changes directory layout, we also needs to change this.
+func imageFSPath(rootDir, snapshotter string) string {
+	return filepath.Join(rootDir, fmt.Sprintf("%s.%s", plugin.SnapshotPlugin, snapshotter))
+}

pkg/server/service_test.go

@@ -24,6 +24,7 @@ import (
 	containerstore "github.com/kubernetes-incubator/cri-containerd/pkg/store/container"
 	imagestore "github.com/kubernetes-incubator/cri-containerd/pkg/store/image"
 	sandboxstore "github.com/kubernetes-incubator/cri-containerd/pkg/store/sandbox"
+	snapshotstore "github.com/kubernetes-incubator/cri-containerd/pkg/store/snapshot"
 )
 
 const (
@@ -32,6 +33,7 @@ const (
 	// TODO(random-liu): Change this to image name after we have complete image
 	// management unit test framework.
 	testSandboxImage = "sha256:c75bebcdd211f41b3a460c7bf82970ed6c75acaab9cd4c9a4e125b03ca113798"
+	testImageFSUUID  = "test-image-fs-uuid"
 )
 
 // newTestCRIContainerdService creates a fake criContainerdService for test.
@@ -41,9 +43,11 @@ func newTestCRIContainerdService() *criContainerdService {
 			RootDir:      testRootDir,
 			SandboxImage: testSandboxImage,
 		},
+		imageFSUUID:        testImageFSUUID,
 		os:                 ostesting.NewFakeOS(),
 		sandboxStore:       sandboxstore.NewStore(),
 		imageStore:         imagestore.NewStore(),
+		snapshotStore:      snapshotstore.NewStore(),
 		sandboxNameIndex:   registrar.NewRegistrar(),
 		containerStore:     containerstore.NewStore(),
 		containerNameIndex: registrar.NewRegistrar(),

pkg/server/snapshots.go

@@ -0,0 +1,110 @@
+/*
+Copyright 2017 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 server
+
+import (
+	"context"
+	"time"
+
+	"github.com/containerd/containerd/errdefs"
+	"github.com/containerd/containerd/snapshot"
+	"github.com/golang/glog"
+
+	snapshotstore "github.com/kubernetes-incubator/cri-containerd/pkg/store/snapshot"
+)
+
+// snapshotsSyncer syncs snapshot stats periodically. imagefs info and container stats
+// should both use cached result here.
+// TODO(random-liu): Benchmark with high workload. We may need a statsSyncer instead if
+// benchmark result shows that container cpu/memory stats also need to be cached.
+type snapshotsSyncer struct {
+	store       *snapshotstore.Store
+	snapshotter snapshot.Snapshotter
+	syncPeriod  time.Duration
+}
+
+// newSnapshotsSyncer creates a snapshot syncer.
+func newSnapshotsSyncer(store *snapshotstore.Store, snapshotter snapshot.Snapshotter,
+	period time.Duration) *snapshotsSyncer {
+	return &snapshotsSyncer{
+		store:       store,
+		snapshotter: snapshotter,
+		syncPeriod:  period,
+	}
+}
+
+// start starts the snapshots syncer. No stop function is needed because
+// the syncer doesn't update any persistent states, it's fine to let it
+// exit with the process.
+func (s *snapshotsSyncer) start() {
+	tick := time.NewTicker(s.syncPeriod)
+	go func() {
+		defer tick.Stop()
+		// TODO(random-liu): This is expensive. We should do benchmark to
+		// check the resource usage and optimize this.
+		for {
+			if err := s.sync(); err != nil {
+				glog.Errorf("Failed to sync snapshot stats: %v", err)
+			}
+			<-tick.C
+		}
+	}()
+}
+
+// sync updates all snapshots stats.
+func (s *snapshotsSyncer) sync() error {
+	start := time.Now().UnixNano()
+	collect := func(ctx context.Context, info snapshot.Info) error {
+		sn, err := s.store.Get(info.Name)
+		if err == nil {
+			// Only update timestamp for non-active snapshot.
+			if sn.Kind == info.Kind && sn.Kind != snapshot.KindActive {
+				sn.Timestamp = time.Now().UnixNano()
+				s.store.Add(sn)
+				return nil
+			}
+		}
+		// Get newest stats if the snapshot is new or active.
+		sn = snapshotstore.Snapshot{
+			Key:       info.Name,
+			Kind:      info.Kind,
+			Timestamp: time.Now().UnixNano(),
+		}
+		usage, err := s.snapshotter.Usage(ctx, info.Name)
+		if err != nil {
+			if errdefs.IsNotFound(err) {
+				return nil
+			}
+			return err
+		}
+		sn.Size = uint64(usage.Size)
+		sn.Inodes = uint64(usage.Inodes)
+		s.store.Add(sn)
+		return nil
+	}
+	if err := s.snapshotter.Walk(context.Background(), collect); err != nil {
+		return err
+	}
+	for _, sn := range s.store.List() {
+		if sn.Timestamp >= start {
+			continue
+		}
+		// Delete the snapshot stats if it's not updated this time.
+		s.store.Delete(sn.Key)
+	}
+	return nil
+}

pkg/store/image/image.go

@@ -92,8 +92,8 @@ func (s *Store) List() []Image {
 	s.lock.RLock()
 	defer s.lock.RUnlock()
 	var images []Image
-	for _, sb := range s.images {
-		images = append(images, sb)
+	for _, i := range s.images {
+		images = append(images, i)
 	}
 	return images
 }

pkg/store/image/image_test.go

@@ -99,7 +99,7 @@ func TestImageStore(t *testing.T) {
 	imgs = s.List()
 	assert.Len(imgs, 2)
 
-	t.Logf("get should return nil after deletion")
+	t.Logf("get should return empty struct and ErrNotExist after deletion")
 	img, err := s.Get(testID)
 	assert.Equal(Image{}, img)
 	assert.Equal(store.ErrNotExist, err)

pkg/store/snapshot/snapshot.go

@@ -0,0 +1,87 @@
+/*
+Copyright 2017 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 snapshot
+
+import (
+	"sync"
+
+	"github.com/containerd/containerd/snapshot"
+
+	"github.com/kubernetes-incubator/cri-containerd/pkg/store"
+)
+
+// Snapshot contains the information about the snapshot.
+type Snapshot struct {
+	// Key is the key of the snapshot
+	Key string
+	// Kind is the kind of the snapshot (active, commited, view)
+	Kind snapshot.Kind
+	// Size is the size of the snapshot in bytes.
+	Size uint64
+	// Inodes is the number of inodes used by the snapshot
+	Inodes uint64
+	// Timestamp is latest update time (in nanoseconds) of the snapshot
+	// information.
+	Timestamp int64
+}
+
+// Store stores all snapshots.
+type Store struct {
+	lock      sync.RWMutex
+	snapshots map[string]Snapshot
+}
+
+// NewStore creates a snapshot store.
+func NewStore() *Store {
+	return &Store{snapshots: make(map[string]Snapshot)}
+}
+
+// Add a snapshot into the store.
+func (s *Store) Add(snapshot Snapshot) {
+	s.lock.Lock()
+	defer s.lock.Unlock()
+	s.snapshots[snapshot.Key] = snapshot
+}
+
+// Get returns the snapshot with specified key. Returns store.ErrNotExist if the
+// snapshot doesn't exist.
+func (s *Store) Get(key string) (Snapshot, error) {
+	s.lock.RLock()
+	defer s.lock.RUnlock()
+	if sn, ok := s.snapshots[key]; ok {
+		return sn, nil
+	}
+	return Snapshot{}, store.ErrNotExist
+}
+
+// List lists all snapshots.
+func (s *Store) List() []Snapshot {
+	s.lock.RLock()
+	defer s.lock.RUnlock()
+	var snapshots []Snapshot
+	for _, sn := range s.snapshots {
+		snapshots = append(snapshots, sn)
+	}
+	return snapshots
+}
+
+// Delete deletes the snapshot with specified key.
+func (s *Store) Delete(key string) {
+	s.lock.Lock()
+	defer s.lock.Unlock()
+	delete(s.snapshots, key)
+}

pkg/store/snapshot/snapshot_test.go

@@ -0,0 +1,84 @@
+/*
+Copyright 2017 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 snapshot
+
+import (
+	"testing"
+	"time"
+
+	"github.com/containerd/containerd/snapshot"
+	assertlib "github.com/stretchr/testify/assert"
+
+	"github.com/kubernetes-incubator/cri-containerd/pkg/store"
+)
+
+func TestSnapshotStore(t *testing.T) {
+	snapshots := map[string]Snapshot{
+		"key1": {
+			Key:       "key1",
+			Kind:      snapshot.KindActive,
+			Size:      10,
+			Inodes:    100,
+			Timestamp: time.Now().UnixNano(),
+		},
+		"key2": {
+			Key:       "key2",
+			Kind:      snapshot.KindCommitted,
+			Size:      20,
+			Inodes:    200,
+			Timestamp: time.Now().UnixNano(),
+		},
+		"key3": {
+			Key:       "key3",
+			Kind:      snapshot.KindView,
+			Size:      0,
+			Inodes:    0,
+			Timestamp: time.Now().UnixNano(),
+		},
+	}
+	assert := assertlib.New(t)
+
+	s := NewStore()
+
+	t.Logf("should be able to add snapshot")
+	for _, sn := range snapshots {
+		s.Add(sn)
+	}
+
+	t.Logf("should be able to get snapshot")
+	for id, sn := range snapshots {
+		got, err := s.Get(id)
+		assert.NoError(err)
+		assert.Equal(sn, got)
+	}
+
+	t.Logf("should be able to list snapshot")
+	sns := s.List()
+	assert.Len(sns, 3)
+
+	testKey := "key2"
+
+	t.Logf("should be able to delete snapshot")
+	s.Delete(testKey)
+	sns = s.List()
+	assert.Len(sns, 2)
+
+	t.Logf("get should return empty struct and ErrNotExist after deletion")
+	sn, err := s.Get(testKey)
+	assert.Equal(Snapshot{}, sn)
+	assert.Equal(store.ErrNotExist, err)
+}