support using multiple snapshotters simultaneously

e.g. dist pull --snapshotter btrfs ...; ctr run --snapshotter btrfs ...
(empty string defaults for overlayfs)

Signed-off-by: Akihiro Suda <suda.akihiro@lab.ntt.co.jp>
Signed-off-by: Michael Crosby <crosbymichael@gmail.com>

cmd/ctr/run.go

@@ -48,7 +48,7 @@ var runCommand = cli.Command{
 	Name:      "run",
 	Usage:     "run a container",
 	ArgsUsage: "IMAGE ID [COMMAND] [ARG...]",
-	Flags: []cli.Flag{
+	Flags: append([]cli.Flag{
 		cli.BoolFlag{
 			Name:  "tty,t",
 			Usage: "allocate a TTY for the container",
@@ -86,7 +86,7 @@ var runCommand = cli.Command{
 			Name:  "checkpoint",
 			Usage: "provide the checkpoint digest to restore the container",
 		},
-	},
+	}, snapshotterFlags...),
 	Action: func(context *cli.Context) error {
 		var (
 			err             error

cmd/ctr/run_unix.go

@@ -106,6 +106,7 @@ func newContainer(ctx gocontext.Context, client *containerd.Client, context *cli
 			containerd.WithSpec(spec),
 			containerd.WithImage(image),
 			containerd.WithContainerLabels(labels),
+			containerd.WithSnapshotter(context.String("snapshotter")),
 			rootfs,
 		)
 	}

cmd/ctr/snapshot.go

@@ -19,6 +19,7 @@ import (
 var snapshotCommand = cli.Command{
 	Name:  "snapshot",
 	Usage: "snapshot management",
+	Flags: snapshotterFlags,
 	Subcommands: cli.Commands{
 		archiveSnapshotCommand,
 		listSnapshotCommand,
@@ -79,13 +80,11 @@ var listSnapshotCommand = cli.Command{
 		ctx, cancel := appContext(clicontext)
 		defer cancel()
 
-		client, err := newClient(clicontext)
+		snapshotter, err := getSnapshotter(clicontext)
 		if err != nil {
 			return err
 		}
 
-		snapshotter := client.SnapshotService()
-
 		tw := tabwriter.NewWriter(os.Stdout, 1, 8, 1, ' ', 0)
 		fmt.Fprintln(tw, "ID\tParent\tState\tReadonly\t")
 
@@ -125,11 +124,6 @@ var usageSnapshotCommand = cli.Command{
 		ctx, cancel := appContext(clicontext)
 		defer cancel()
 
-		client, err := newClient(clicontext)
-		if err != nil {
-			return err
-		}
-
 		var displaySize func(int64) string
 		if clicontext.Bool("b") {
 			displaySize = func(s int64) string {
@@ -141,7 +135,10 @@ var usageSnapshotCommand = cli.Command{
 			}
 		}
 
-		snapshotter := client.SnapshotService()
+		snapshotter, err := getSnapshotter(clicontext)
+		if err != nil {
+			return err
+		}
 
 		tw := tabwriter.NewWriter(os.Stdout, 1, 8, 1, ' ', 0)
 		fmt.Fprintln(tw, "ID\tSize\tInodes\t")
@@ -180,13 +177,11 @@ var removeSnapshotCommand = cli.Command{
 		ctx, cancel := appContext(clicontext)
 		defer cancel()
 
-		client, err := newClient(clicontext)
+		snapshotter, err := getSnapshotter(clicontext)
 		if err != nil {
 			return err
 		}
 
-		snapshotter := client.SnapshotService()
-
 		for _, id := range clicontext.Args() {
 			err = snapshotter.Remove(ctx, id)
 			if err != nil {
@@ -219,12 +214,11 @@ var prepareSnapshotCommand = cli.Command{
 
 		logrus.Infof("preparing mounts %s", dgst.String())
 
-		client, err := newClient(clicontext)
+		snapshotter, err := getSnapshotter(clicontext)
 		if err != nil {
 			return err
 		}
 
-		snapshotter := client.SnapshotService()
 		mounts, err := snapshotter.Prepare(ctx, target, dgst.String())
 		if err != nil {
 			return err

cmd/ctr/utils.go

@@ -35,6 +35,13 @@ import (
 	"google.golang.org/grpc"
 )
 
+var snapshotterFlags = []cli.Flag{
+	cli.StringFlag{
+		Name:  "snapshotter",
+		Usage: "Snapshotter name. Empty value stands for the daemon default value.",
+	},
+}
+
 var grpcConn *grpc.ClientConn
 
 // appContext returns the context for a command. Should only be called once per
@@ -111,7 +118,7 @@ func getSnapshotter(context *cli.Context) (snapshot.Snapshotter, error) {
 	if err != nil {
 		return nil, err
 	}
-	return snapshotservice.NewSnapshotterFromClient(snapshotapi.NewSnapshotsClient(conn)), nil
+	return snapshotservice.NewSnapshotterFromClient(snapshotapi.NewSnapshotsClient(conn), context.GlobalString("snapshotter")), nil
 }
 
 func getImageStore(clicontext *cli.Context) (images.Store, error) {

cmd/dist/common.go

@@ -44,6 +44,13 @@ var registryFlags = []cli.Flag{
 	},
 }
 
+var snapshotterFlags = []cli.Flag{
+	cli.StringFlag{
+		Name:  "snapshotter",
+		Usage: "Snapshotter name. Empty value stands for the daemon default value.",
+	},
+}
+
 func getClient(context *cli.Context) (*containerd.Client, error) {
 	address := context.GlobalString("address")
 	//timeout := context.GlobalDuration("connect-timeout")

cmd/dist/pull.go

@@ -20,7 +20,7 @@ command. As part of this process, we do the following:
 2. Prepare the snapshot filesystem with the pulled resources.
 3. Register metadata for the image.
 `,
-	Flags: registryFlags,
+	Flags: append(registryFlags, snapshotterFlags...),
 	Action: func(clicontext *cli.Context) error {
 		var (
 			ref = clicontext.Args().First()
@@ -38,7 +38,7 @@ command. As part of this process, we do the following:
 
 		// TODO: Show unpack status
 		fmt.Printf("unpacking %s...", img.Target().Digest)
-		err = img.Unpack(ctx)
+		err = img.Unpack(ctx, clicontext.String("snapshotter"))
 		fmt.Println("done")
 		return err
 	},

cmd/dist/rootfs.go

@@ -21,7 +21,7 @@ var rootfsUnpackCommand = cli.Command{
 	Name:      "unpack",
 	Usage:     "unpack applies layers from a manifest to a snapshot",
 	ArgsUsage: "[flags] <digest>",
-	Flags:     []cli.Flag{},
+	Flags:     snapshotterFlags,
 	Action: func(clicontext *cli.Context) error {
 		ctx, cancel := appContext(clicontext)
 		defer cancel()
@@ -49,7 +49,7 @@ var rootfsUnpackCommand = cli.Command{
 		for _, image := range images {
 			if image.Target().Digest == dgst {
 				fmt.Printf("unpacking %s (%s)...", dgst, image.Target().MediaType)
-				if err := image.Unpack(ctx); err != nil {
+				if err := image.Unpack(ctx, clicontext.String("snapshotter")); err != nil {
 					fmt.Println()
 					return err
 				}