Add diff service implementation

Add snapshot subcommand to ctr for creating diffs of RW layers.

Signed-off-by: Derek McGowan <derek@mcgstyle.net>

archive/tar.go

@@ -40,13 +40,7 @@ func Diff(ctx context.Context, a, b string) io.ReadCloser {
 	r, w := io.Pipe()
 
 	go func() {
-		var err error
+		err := WriteDiff(ctx, w, a, b)
-		cw := newChangeWriter(w, b)
-		if err = fs.Changes(ctx, a, b, cw.HandleChange); err != nil {
-			err = errors.Wrap(err, "failed to create diff tar stream")
-		} else {
-			err = cw.Close()
-		}
 		if err = w.CloseWithError(err); err != nil {
 			log.G(ctx).WithError(err).Debugf("closing tar pipe failed")
 		}
@@ -55,6 +49,22 @@ func Diff(ctx context.Context, a, b string) io.ReadCloser {
 	return r
 }
 
+// WriteDiff writes a tar stream of the computed difference between the
+// provided directories.
+//
+// Produces a tar using OCI style file markers for deletions. Deleted
+// files will be prepended with the prefix ".wh.". This style is
+// based off AUFS whiteouts.
+// See https://github.com/opencontainers/image-spec/blob/master/layer.md
+func WriteDiff(ctx context.Context, w io.Writer, a, b string) error {
+	cw := newChangeWriter(w, b)
+	err := fs.Changes(ctx, a, b, cw.HandleChange)
+	if err != nil {
+		return errors.Wrap(err, "failed to create diff tar stream")
+	}
+	return cw.Close()
+}
+
 const (
 	// whiteoutPrefix prefix means file is a whiteout. If this is followed by a
 	// filename this means that file has been removed from the base layer.

cmd/ctr/main.go

@@ -61,6 +61,7 @@ containerd client
 		execCommand,
 		pauseCommand,
 		resumeCommand,
+		snapshotCommand,
 		versionCommand,
 	}
 	app.Commands = append(app.Commands, extraCmds...)

cmd/ctr/run.go

@@ -54,6 +54,10 @@ var runCommand = cli.Command{
 			Name:  "net-host",
 			Usage: "enable host networking for the container",
 		},
+		cli.BoolFlag{
+			Name:  "keep",
+			Usage: "keep container after running",
+		},
 	},
 	Action: func(context *cli.Context) error {
 		var (
@@ -110,7 +114,11 @@ var runCommand = cli.Command{
 				return err
 			}
 
-			mounts, err = snapshotter.Prepare(ctx, id, identity.ChainID(diffIDs).String())
+			if context.Bool("readonly") {
+				mounts, err = snapshotter.View(ctx, id, identity.ChainID(diffIDs).String())
+			} else {
+				mounts, err = snapshotter.Prepare(ctx, id, identity.ChainID(diffIDs).String())
+			}
 			if err != nil {
 				if !snapshot.IsExist(err) {
 					return err
@@ -192,10 +200,12 @@ var runCommand = cli.Command{
 		if err != nil {
 			return err
 		}
-		if _, err := containers.Delete(ctx, &execution.DeleteRequest{
+		if !context.Bool("keep") {
-			ID: response.ID,
+			if _, err := containers.Delete(ctx, &execution.DeleteRequest{
-		}); err != nil {
+				ID: response.ID,
-			return err
+			}); err != nil {
+				return err
+			}
 		}
 		if status != 0 {
 			return cli.NewExitError("", int(status))

cmd/ctr/snapshot.go

@@ -0,0 +1,50 @@
+package main
+
+import (
+	"context"
+	"errors"
+	"fmt"
+
+	"github.com/containerd/containerd/rootfs"
+	"github.com/urfave/cli"
+)
+
+var snapshotCommand = cli.Command{
+	Name:      "snapshot",
+	Usage:     "snapshot a container into an archive",
+	ArgsUsage: "",
+	Flags: []cli.Flag{
+		cli.StringFlag{
+			Name:  "id",
+			Usage: "id of the container",
+		},
+	},
+	Action: func(clicontext *cli.Context) error {
+		id := clicontext.String("id")
+		if id == "" {
+			return errors.New("container id must be provided")
+		}
+
+		snapshotter, err := getSnapshotter(clicontext)
+		if err != nil {
+			return err
+		}
+
+		differ, err := getDiffService(clicontext)
+		if err != nil {
+			return err
+		}
+
+		contentRef := fmt.Sprintf("diff-%s", id)
+
+		d, err := rootfs.Diff(context.TODO(), id, contentRef, snapshotter, differ)
+		if err != nil {
+			return err
+		}
+
+		// TODO: Track progress
+		fmt.Printf("%s %s\n", d.MediaType, d.Digest)
+
+		return nil
+	},
+}

cmd/ctr/utils.go

@@ -13,6 +13,7 @@ import (
 
 	"github.com/Sirupsen/logrus"
 	contentapi "github.com/containerd/containerd/api/services/content"
+	diffapi "github.com/containerd/containerd/api/services/diff"
 	"github.com/containerd/containerd/api/services/execution"
 	imagesapi "github.com/containerd/containerd/api/services/images"
 	snapshotapi "github.com/containerd/containerd/api/services/snapshot"
@@ -21,6 +22,7 @@ import (
 	"github.com/containerd/containerd/content"
 	"github.com/containerd/containerd/images"
 	contentservice "github.com/containerd/containerd/services/content"
+	"github.com/containerd/containerd/services/diff"
 	imagesservice "github.com/containerd/containerd/services/images"
 	snapshotservice "github.com/containerd/containerd/services/snapshot"
 	"github.com/containerd/containerd/snapshot"
@@ -62,6 +64,14 @@ func getImageStore(clicontext *cli.Context) (images.Store, error) {
 	return imagesservice.NewStoreFromClient(imagesapi.NewImagesClient(conn)), nil
 }
 
+func getDiffService(context *cli.Context) (diff.DiffService, error) {
+	conn, err := getGRPCConnection(context)
+	if err != nil {
+		return nil, err
+	}
+	return diff.NewDiffServiceFromClient(diffapi.NewDiffClient(conn)), nil
+}
+
 func getVersionService(context *cli.Context) (versionservice.VersionClient, error) {
 	conn, err := getGRPCConnection(context)
 	if err != nil {

cmd/dist/pull.go

@@ -116,7 +116,7 @@ command. As part of this process, we do the following:
 				log.G(ctx).Fatal(err)
 			}
 			snapshotter := snapshotservice.NewSnapshotterFromClient(snapshotapi.NewSnapshotClient(conn))
-			applier := diffservice.NewApplierFromClient(diffapi.NewDiffClient(conn))
+			applier := diffservice.NewDiffServiceFromClient(diffapi.NewDiffClient(conn))
 
 			log.G(ctx).Info("unpacking rootfs")
 

cmd/dist/rootfs.go

@@ -65,7 +65,7 @@ var rootfsUnpackCommand = cli.Command{
 		}
 
 		snapshotter := snapshotservice.NewSnapshotterFromClient(snapshotapi.NewSnapshotClient(conn))
-		applier := diffservice.NewApplierFromClient(diffapi.NewDiffClient(conn))
+		applier := diffservice.NewDiffServiceFromClient(diffapi.NewDiffClient(conn))
 
 		chainID, err := rootfs.ApplyLayers(ctx, layers, snapshotter, applier)
 		if err != nil {

rootfs/diff.go

@@ -0,0 +1,52 @@
+package rootfs
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/containerd/containerd"
+	"github.com/containerd/containerd/content"
+	"github.com/containerd/containerd/snapshot"
+	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
+)
+
+type MountDiffer interface {
+	DiffMounts(ctx context.Context, lower, upper []containerd.Mount, media, ref string) (ocispec.Descriptor, error)
+}
+
+type DiffOptions struct {
+	MountDiffer
+	content.Store
+	snapshot.Snapshotter
+}
+
+func Diff(ctx context.Context, snapshotID, contentRef string, sn snapshot.Snapshotter, md MountDiffer) (ocispec.Descriptor, error) {
+	info, err := sn.Stat(ctx, snapshotID)
+	if err != nil {
+		return ocispec.Descriptor{}, err
+	}
+
+	lowerKey := fmt.Sprintf("%s-parent-view", info.Parent)
+	lower, err := sn.View(ctx, lowerKey, info.Parent)
+	if err != nil {
+		return ocispec.Descriptor{}, err
+	}
+	defer sn.Remove(ctx, lowerKey)
+
+	var upper []containerd.Mount
+	if info.Kind == snapshot.KindActive {
+		upper, err = sn.Mounts(ctx, snapshotID)
+		if err != nil {
+			return ocispec.Descriptor{}, err
+		}
+	} else {
+		upperKey := fmt.Sprintf("%s-view", snapshotID)
+		upper, err = sn.View(ctx, upperKey, snapshotID)
+		if err != nil {
+			return ocispec.Descriptor{}, err
+		}
+		defer sn.Remove(ctx, lowerKey)
+	}
+
+	return md.DiffMounts(ctx, lower, upper, ocispec.MediaTypeImageLayer, contentRef)
+}

services/diff/client.go

@@ -11,19 +11,24 @@ import (
 	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
 )
 
+type DiffService interface {
+	rootfs.Applier
+	rootfs.MountDiffer
+}
+
 // NewApplierFromClient returns a new Applier which communicates
 // over a GRPC connection.
-func NewApplierFromClient(client diffapi.DiffClient) rootfs.Applier {
+func NewDiffServiceFromClient(client diffapi.DiffClient) DiffService {
-	return &remoteApplier{
+	return &remote{
 		client: client,
 	}
 }
 
-type remoteApplier struct {
+type remote struct {
 	client diffapi.DiffClient
 }
 
-func (r *remoteApplier) Apply(ctx context.Context, diff ocispec.Descriptor, mounts []containerd.Mount) (ocispec.Descriptor, error) {
+func (r *remote) Apply(ctx context.Context, diff ocispec.Descriptor, mounts []containerd.Mount) (ocispec.Descriptor, error) {
 	req := &diffapi.ApplyRequest{
 		Diff:   fromDescriptor(diff),
 		Mounts: fromMounts(mounts),
@@ -35,6 +40,20 @@ func (r *remoteApplier) Apply(ctx context.Context, diff ocispec.Descriptor, moun
 	return toDescriptor(resp.Applied), nil
 }
 
+func (r *remote) DiffMounts(ctx context.Context, a, b []containerd.Mount, media, ref string) (ocispec.Descriptor, error) {
+	req := &diffapi.DiffRequest{
+		Left:      fromMounts(a),
+		Right:     fromMounts(b),
+		MediaType: media,
+		Ref:       ref,
+	}
+	resp, err := r.client.Diff(ctx, req)
+	if err != nil {
+		return ocispec.Descriptor{}, err
+	}
+	return toDescriptor(resp.Diff), nil
+}
+
 func fromDescriptor(d ocispec.Descriptor) *descriptor.Descriptor {
 	return &descriptor.Descriptor{
 		MediaType: d.MediaType,

services/diff/service.go

@@ -102,8 +102,73 @@ func (s *service) Apply(ctx context.Context, er *diffapi.ApplyRequest) (*diffapi
 	return resp, nil
 }
 
-func (s *service) Diff(context.Context, *diffapi.DiffRequest) (*diffapi.DiffResponse, error) {
+func (s *service) Diff(ctx context.Context, dr *diffapi.DiffRequest) (*diffapi.DiffResponse, error) {
-	return nil, errors.New("not implemented")
+	aMounts := toMounts(dr.Left)
+	bMounts := toMounts(dr.Right)
+
+	aDir, err := ioutil.TempDir("", "left-")
+	if err != nil {
+		return nil, errors.Wrap(err, "failed to create temporary directory")
+	}
+	defer os.RemoveAll(aDir)
+
+	bDir, err := ioutil.TempDir("", "right-")
+	if err != nil {
+		return nil, errors.Wrap(err, "failed to create temporary directory")
+	}
+	defer os.RemoveAll(bDir)
+
+	if err := containerd.MountAll(aMounts, aDir); err != nil {
+		return nil, errors.Wrap(err, "failed to mount")
+	}
+	defer containerd.Unmount(aDir, 0)
+
+	if err := containerd.MountAll(bMounts, bDir); err != nil {
+		return nil, errors.Wrap(err, "failed to mount")
+	}
+	defer containerd.Unmount(bDir, 0)
+
+	cw, err := s.store.Writer(ctx, dr.Ref, 0, "")
+	if err != nil {
+		return nil, errors.Wrap(err, "failed to open writer")
+	}
+
+	// TODO: Validate media type
+
+	// TODO: Support compressed media types (link compressed to uncompressed)
+	//dgstr := digest.SHA256.Digester()
+	//wc := &writeCounter{}
+	//compressed, err := compression.CompressStream(cw, compression.Gzip)
+	//if err != nil {
+	//	return nil, errors.Wrap(err, "failed to get compressed stream")
+	//}
+	//err = archive.WriteDiff(ctx, io.MultiWriter(compressed, dgstr.Hash(), wc), lowerDir, upperDir)
+	//compressed.Close()
+
+	err = archive.WriteDiff(ctx, cw, aDir, bDir)
+	if err != nil {
+		return nil, errors.Wrap(err, "failed to write diff")
+	}
+
+	dgst := cw.Digest()
+	if err := cw.Commit(0, dgst); err != nil {
+		return nil, errors.Wrap(err, "failed to commit")
+	}
+
+	info, err := s.store.Info(ctx, dgst)
+	if err != nil {
+		return nil, errors.Wrap(err, "failed to get info from content store")
+	}
+
+	desc := ocispec.Descriptor{
+		MediaType: dr.MediaType,
+		Digest:    info.Digest,
+		Size:      info.Size,
+	}
+
+	return &diffapi.DiffResponse{
+		Diff: fromDescriptor(desc),
+	}, nil
 }
 
 type readCounter struct {