Merge pull request #1393 from dmcgowan/multiple-differs

Add support for multiple differs

differ/differ.go

@@ -4,11 +4,14 @@ import (
 	"io"
 	"io/ioutil"
 	"os"
+	"strings"
 
 	"github.com/boltdb/bolt"
 	"github.com/containerd/containerd/archive"
 	"github.com/containerd/containerd/archive/compression"
 	"github.com/containerd/containerd/content"
+	"github.com/containerd/containerd/errdefs"
+	"github.com/containerd/containerd/images"
 	"github.com/containerd/containerd/metadata"
 	"github.com/containerd/containerd/mount"
 	"github.com/containerd/containerd/plugin"
@@ -21,7 +24,7 @@ import (
 func init() {
 	plugin.Register(&plugin.Registration{
 		Type: plugin.DiffPlugin,
-		ID:   "base-diff",
+		ID:   "walking",
 		Requires: []plugin.PluginType{
 			plugin.ContentPlugin,
 			plugin.MetadataPlugin,
@@ -35,27 +38,38 @@ func init() {
 			if err != nil {
 				return nil, err
 			}
-			return NewBaseDiff(metadata.NewContentStore(md.(*bolt.DB), c.(content.Store)))
+			return newWalkingDiff(metadata.NewContentStore(md.(*bolt.DB), c.(content.Store)))
 		},
 	})
 }
 
-type BaseDiff struct {
+type walkingDiff struct {
 	store content.Store
 }
 
-var _ plugin.Differ = &BaseDiff{}
-
 var emptyDesc = ocispec.Descriptor{}
 
-func NewBaseDiff(store content.Store) (*BaseDiff, error) {
+func newWalkingDiff(store content.Store) (plugin.Differ, error) {
-	return &BaseDiff{
+	return &walkingDiff{
 		store: store,
 	}, nil
 }
 
-func (s *BaseDiff) Apply(ctx context.Context, desc ocispec.Descriptor, mounts []mount.Mount) (ocispec.Descriptor, error) {
+func (s *walkingDiff) Apply(ctx context.Context, desc ocispec.Descriptor, mounts []mount.Mount) (ocispec.Descriptor, error) {
-	// TODO: Check for supported media types
+	var isCompressed bool
+	switch desc.MediaType {
+	case ocispec.MediaTypeImageLayer, images.MediaTypeDockerSchema2Layer:
+	case ocispec.MediaTypeImageLayerGzip, images.MediaTypeDockerSchema2LayerGzip:
+		isCompressed = true
+	default:
+		// Still apply all generic media types *.tar[.+]gzip and *.tar
+		if strings.HasSuffix(desc.MediaType, ".tar.gzip") || strings.HasSuffix(desc.MediaType, ".tar+gzip") {
+			isCompressed = true
+		} else if !strings.HasSuffix(desc.MediaType, ".tar") {
+			return emptyDesc, errors.Wrapf(errdefs.ErrNotSupported, "unsupported diff media type: %v", desc.MediaType)
+		}
+	}
+
 	dir, err := ioutil.TempDir("", "extract-")
 	if err != nil {
 		return emptyDesc, errors.Wrap(err, "failed to create temporary directory")
@@ -67,22 +81,25 @@ func (s *BaseDiff) Apply(ctx context.Context, desc ocispec.Descriptor, mounts []
 	}
 	defer mount.Unmount(dir, 0)
 
-	r, err := s.store.ReaderAt(ctx, desc.Digest)
+	ra, err := s.store.ReaderAt(ctx, desc.Digest)
 	if err != nil {
 		return emptyDesc, errors.Wrap(err, "failed to get reader from content store")
 	}
-	defer r.Close()
+	defer ra.Close()
 
-	// TODO: only decompress stream if media type is compressed
+	r := content.NewReader(ra)
-	ds, err := compression.DecompressStream(content.NewReader(r))
+	if isCompressed {
-	if err != nil {
+		ds, err := compression.DecompressStream(r)
-		return emptyDesc, err
+		if err != nil {
+			return emptyDesc, err
+		}
+		defer ds.Close()
+		r = ds
 	}
-	defer ds.Close()
 
 	digester := digest.Canonical.Digester()
 	rc := &readCounter{
-		r: io.TeeReader(ds, digester.Hash()),
+		r: io.TeeReader(r, digester.Hash()),
 	}
 
 	if _, err := archive.Apply(ctx, dir, rc); err != nil {
@@ -101,7 +118,7 @@ func (s *BaseDiff) Apply(ctx context.Context, desc ocispec.Descriptor, mounts []
 	}, nil
 }
 
-func (s *BaseDiff) DiffMounts(ctx context.Context, lower, upper []mount.Mount, media, ref string) (ocispec.Descriptor, error) {
+func (s *walkingDiff) DiffMounts(ctx context.Context, lower, upper []mount.Mount, media, ref string) (ocispec.Descriptor, error) {
 	var isCompressed bool
 	switch media {
 	case ocispec.MediaTypeImageLayer:
@@ -111,7 +128,7 @@ func (s *BaseDiff) DiffMounts(ctx context.Context, lower, upper []mount.Mount, m
 		media = ocispec.MediaTypeImageLayerGzip
 		isCompressed = true
 	default:
-		return emptyDesc, errors.Errorf("unsupported diff media type: %v", media)
+		return emptyDesc, errors.Wrapf(errdefs.ErrNotSupported, "unsupported diff media type: %v", media)
 	}
 	aDir, err := ioutil.TempDir("", "left-")
 	if err != nil {

errdefs/errors.go

@@ -26,6 +26,7 @@ var (
 	ErrAlreadyExists      = errors.New("already exists")
 	ErrFailedPrecondition = errors.New("failed precondition")
 	ErrUnavailable        = errors.New("unavailable")
+	ErrNotSupported       = errors.New("not supported") // represents not supported and unimplemented
 )
 
 func IsInvalidArgument(err error) bool {
@@ -52,3 +53,7 @@ func IsFailedPrecondition(err error) bool {
 func IsUnavailable(err error) bool {
 	return errors.Cause(err) == ErrUnavailable
 }
+
+func IsNotSupported(err error) bool {
+	return errors.Cause(err) == ErrNotSupported
+}

errdefs/grpc.go

@@ -38,6 +38,8 @@ func ToGRPC(err error) error {
 		return grpc.Errorf(codes.FailedPrecondition, err.Error())
 	case IsUnavailable(err):
 		return grpc.Errorf(codes.Unavailable, err.Error())
+	case IsNotSupported(err):
+		return grpc.Errorf(codes.Unimplemented, err.Error())
 	}
 
 	return err
@@ -69,6 +71,8 @@ func FromGRPC(err error) error {
 		cls = ErrUnavailable
 	case codes.FailedPrecondition:
 		cls = ErrFailedPrecondition
+	case codes.Unimplemented:
+		cls = ErrNotSupported
 	default:
 		cls = ErrUnknown
 	}

services/diff/service.go

@@ -6,10 +6,22 @@ import (
 	"github.com/containerd/containerd/errdefs"
 	"github.com/containerd/containerd/mount"
 	"github.com/containerd/containerd/plugin"
+	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
+	"github.com/pkg/errors"
 	"golang.org/x/net/context"
 	"google.golang.org/grpc"
 )
 
+type config struct {
+	// Order is the order of preference in which to try diff algorithms, the
+	// first differ which is supported is used.
+	// Note when multiple differs may be supported, this order will be
+	// respected for which is choosen. Each differ should return the same
+	// correct output, allowing any ordering to be used to prefer
+	// more optimimal implementations.
+	Order []string `toml:"default,omitempty"`
+}
+
 func init() {
 	plugin.Register(&plugin.Registration{
 		Type: plugin.GRPCPlugin,
@@ -17,20 +29,34 @@ func init() {
 		Requires: []plugin.PluginType{
 			plugin.DiffPlugin,
 		},
+		Config: &config{
+			Order: []string{"walking"},
+		},
 		Init: func(ic *plugin.InitContext) (interface{}, error) {
-			d, err := ic.Get(plugin.DiffPlugin)
+			differs, err := ic.GetAll(plugin.DiffPlugin)
 			if err != nil {
 				return nil, err
 			}
+
+			orderedNames := ic.Config.(*config).Order
+			ordered := make([]plugin.Differ, len(orderedNames))
+			for i, n := range orderedNames {
+				differ, ok := differs[n]
+				if !ok {
+					return nil, errors.Errorf("needed differ not loaded: %s", n)
+				}
+				ordered[i] = differ.(plugin.Differ)
+			}
+
 			return &service{
-				diff: d.(plugin.Differ),
+				differs: ordered,
 			}, nil
 		},
 	})
 }
 
 type service struct {
-	diff plugin.Differ
+	differs []plugin.Differ
 }
 
 func (s *service) Register(gs *grpc.Server) error {
@@ -39,12 +65,20 @@ func (s *service) Register(gs *grpc.Server) error {
 }
 
 func (s *service) Apply(ctx context.Context, er *diffapi.ApplyRequest) (*diffapi.ApplyResponse, error) {
-	desc := toDescriptor(er.Diff)
+	var (
-	// TODO: Check for supported media types
+		ocidesc ocispec.Descriptor
+		err     error
+		desc    = toDescriptor(er.Diff)
+		mounts  = toMounts(er.Mounts)
+	)
 
-	mounts := toMounts(er.Mounts)
+	for _, differ := range s.differs {
+		ocidesc, err = differ.Apply(ctx, desc, mounts)
+		if !errdefs.IsNotSupported(err) {
+			break
+		}
+	}
 
-	ocidesc, err := s.diff.Apply(ctx, desc, mounts)
 	if err != nil {
 		return nil, errdefs.ToGRPC(err)
 	}
@@ -56,10 +90,19 @@ func (s *service) Apply(ctx context.Context, er *diffapi.ApplyRequest) (*diffapi
 }
 
 func (s *service) Diff(ctx context.Context, dr *diffapi.DiffRequest) (*diffapi.DiffResponse, error) {
-	aMounts := toMounts(dr.Left)
+	var (
-	bMounts := toMounts(dr.Right)
+		ocidesc ocispec.Descriptor
+		err     error
+		aMounts = toMounts(dr.Left)
+		bMounts = toMounts(dr.Right)
+	)
 
-	ocidesc, err := s.diff.DiffMounts(ctx, aMounts, bMounts, dr.MediaType, dr.Ref)
+	for _, differ := range s.differs {
+		ocidesc, err = differ.DiffMounts(ctx, aMounts, bMounts, dr.MediaType, dr.Ref)
+		if !errdefs.IsNotSupported(err) {
+			break
+		}
+	}
 	if err != nil {
 		return nil, errdefs.ToGRPC(err)
 	}