feat(daemon): lazy image saving

pkg/v1/daemon/image.go

@@ -24,8 +24,15 @@ import (
 	"github.com/google/go-containerregistry/pkg/name"
 	v1 "github.com/google/go-containerregistry/pkg/v1"
 	"github.com/google/go-containerregistry/pkg/v1/tarball"
+	"github.com/google/go-containerregistry/pkg/v1/types"
 )
 
+type image struct {
+	ref          name.Reference
+	opener       *imageOpener
+	tarballImage v1.Image
+}
+
 type imageOpener struct {
 	ref name.Reference
 	ctx context.Context
@@ -85,5 +92,98 @@ func Image(ref name.Reference, options ...Option) (v1.Image, error) {
 		ctx:      o.ctx,
 	}
 
-	return tarball.Image(i.opener(), nil)
+	return &image{
+		ref:    ref,
+		opener: i,
+	}, nil
+}
+
+func (i *image) initialize() error {
+	// Don't re-initialize tarball if already initialized.
+	if i.tarballImage == nil {
+		var err error
+		i.tarballImage, err = tarball.Image(i.opener.opener(), nil)
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func (i *image) Layers() ([]v1.Layer, error) {
+	if err := i.initialize(); err != nil {
+		return nil, err
+	}
+	return i.tarballImage.Layers()
+}
+
+func (i image) MediaType() (types.MediaType, error) {
+	if err := i.initialize(); err != nil {
+		return "", err
+	}
+	return i.tarballImage.MediaType()
+}
+
+func (i *image) Size() (int64, error) {
+	if err := i.initialize(); err != nil {
+		return 0, err
+	}
+	return i.tarballImage.Size()
+}
+
+func (i *image) ConfigName() (v1.Hash, error) {
+	res, _, err := i.opener.client.ImageInspectWithRaw(i.opener.ctx, i.ref.String())
+	if err != nil {
+		return v1.Hash{}, err
+	}
+	return v1.NewHash(res.ID)
+}
+
+func (i image) ConfigFile() (*v1.ConfigFile, error) {
+	if err := i.initialize(); err != nil {
+		return nil, err
+	}
+	return i.tarballImage.ConfigFile()
+}
+
+func (i image) RawConfigFile() ([]byte, error) {
+	if err := i.initialize(); err != nil {
+		return nil, err
+	}
+	return i.tarballImage.RawConfigFile()
+}
+
+func (i image) Digest() (v1.Hash, error) {
+	if err := i.initialize(); err != nil {
+		return v1.Hash{}, err
+	}
+	return i.tarballImage.Digest()
+}
+
+func (i image) Manifest() (*v1.Manifest, error) {
+	if err := i.initialize(); err != nil {
+		return nil, err
+	}
+	return i.tarballImage.Manifest()
+}
+
+func (i image) RawManifest() ([]byte, error) {
+	if err := i.initialize(); err != nil {
+		return nil, err
+	}
+	return i.tarballImage.RawManifest()
+}
+
+func (i image) LayerByDigest(h v1.Hash) (v1.Layer, error) {
+	if err := i.initialize(); err != nil {
+		return nil, err
+	}
+	return i.tarballImage.LayerByDigest(h)
+}
+
+func (i image) LayerByDiffID(h v1.Hash) (v1.Layer, error) {
+	if err := i.initialize(); err != nil {
+		return nil, err
+	}
+	return i.tarballImage.LayerByDiffID(h)
 }

pkg/v1/daemon/image_test.go

@@ -24,10 +24,11 @@ import (
 	"strings"
 	"testing"
 
+	"github.com/docker/docker/api/types"
 	"github.com/google/go-containerregistry/internal/compare"
 	"github.com/google/go-containerregistry/pkg/name"
-
 	"github.com/google/go-containerregistry/pkg/v1/tarball"
+	"github.com/google/go-containerregistry/pkg/v1/validate"
 )
 
 var imagePath = "../tarball/testdata/test_image_1.tar"
@@ -62,6 +63,12 @@ func (m *MockClient) ImageSave(_ context.Context, _ []string) (io.ReadCloser, er
 	return m.saveBody, m.saveErr
 }
 
+func (m *MockClient) ImageInspectWithRaw(context.Context, string) (types.ImageInspect, []byte, error) {
+	return types.ImageInspect{
+		ID: "sha256:6e0b05049ed9c17d02e1a55e80d6599dbfcce7f4f4b022e3c673e685789c470e",
+	}, nil, nil
+}
+
 func TestImage(t *testing.T) {
 	for _, tc := range []struct {
 		name         string
@@ -114,8 +121,22 @@ func TestImage(t *testing.T) {
 				}
 				return
 			}
-			if err := compare.Images(img, dmn); err != nil {
-				t.Errorf("compare.Images: %v", err)
+			err = compare.Images(img, dmn)
+			if err != nil {
+				if tc.wantErr == "" {
+					t.Errorf("compare.Images: %v", err)
+				} else if !strings.Contains(err.Error(), tc.wantErr) {
+					t.Errorf("wanted %s to contain %s", err.Error(), tc.wantErr)
+				}
+			}
+
+			err = validate.Image(dmn)
+			if err != nil {
+				if tc.wantErr == "" {
+					t.Errorf("validate.Image: %v", err)
+				} else if !strings.Contains(err.Error(), tc.wantErr) {
+					t.Errorf("wanted %s to contain %s", err.Error(), tc.wantErr)
+				}
 			}
 		}
 

pkg/v1/daemon/options.go

@@ -99,4 +99,5 @@ type Client interface {
 	ImageSave(context.Context, []string) (io.ReadCloser, error)
 	ImageLoad(context.Context, io.Reader, bool) (types.ImageLoadResponse, error)
 	ImageTag(context.Context, string, string) error
+	ImageInspectWithRaw(context.Context, string) (types.ImageInspect, []byte, error)
 }