containerd/save: Export only present platform manifests

daemon/containerd/image_exporter.go

@@ -5,34 +5,17 @@ import (
 	"io"
 
 	"github.com/containerd/containerd"
+	cerrdefs "github.com/containerd/containerd/errdefs"
+	containerdimages "github.com/containerd/containerd/images"
 	"github.com/containerd/containerd/images/archive"
+	"github.com/containerd/containerd/images/converter"
 	"github.com/containerd/containerd/platforms"
 	"github.com/docker/distribution/reference"
+	"github.com/opencontainers/image-spec/specs-go/v1"
 	"github.com/pkg/errors"
 	"github.com/sirupsen/logrus"
 )
 
-// ExportImage exports a list of images to the given output stream. The
-// exported images are archived into a tar when written to the output
-// stream. All images with the given tag and all versions containing
-// the same tag are exported. names is the set of tags to export, and
-// outStream is the writer which the images are written to.
-func (i *ImageService) ExportImage(ctx context.Context, names []string, outStream io.Writer) error {
-	opts := []archive.ExportOpt{
-		archive.WithPlatform(platforms.Ordered(platforms.DefaultSpec())),
-		archive.WithSkipNonDistributableBlobs(),
-	}
-	is := i.client.ImageService()
-	for _, imageRef := range names {
-		named, err := reference.ParseDockerRef(imageRef)
-		if err != nil {
-			return err
-		}
-		opts = append(opts, archive.WithImage(is, named.String()))
-	}
-	return i.client.Export(ctx, outStream, opts...)
-}
-
 // LoadImage uploads a set of images into the repository. This is the
 // complement of ExportImage.  The input stream is an uncompressed tar
 // ball containing images and metadata.
@@ -64,3 +47,82 @@ func (i *ImageService) LoadImage(ctx context.Context, inTar io.ReadCloser, outSt
 	}
 	return nil
 }
+
+// ExportImage exports a list of images to the given output stream. The
+// exported images are archived into a tar when written to the output
+// stream. All images with the given tag and all versions containing
+// the same tag are exported. names is the set of tags to export, and
+// outStream is the writer which the images are written to.
+func (i *ImageService) ExportImage(ctx context.Context, names []string, outStream io.Writer) error {
+	opts := []archive.ExportOpt{
+		archive.WithSkipNonDistributableBlobs(),
+	}
+
+	for _, imageRef := range names {
+		var err error
+		opts, err = i.appendImageForExport(ctx, opts, imageRef)
+		if err != nil {
+			return err
+		}
+	}
+
+	return i.client.Export(ctx, outStream, opts...)
+}
+
+func (i *ImageService) appendImageForExport(ctx context.Context, opts []archive.ExportOpt, name string) ([]archive.ExportOpt, error) {
+	ref, err := reference.ParseDockerRef(name)
+	if err != nil {
+		return opts, err
+	}
+
+	is := i.client.ImageService()
+
+	img, err := is.Get(ctx, ref.String())
+	if err != nil {
+		return opts, err
+	}
+
+	store := i.client.ContentStore()
+
+	if containerdimages.IsIndexType(img.Target.MediaType) {
+		children, err := containerdimages.Children(ctx, store, img.Target)
+		if err != nil {
+			return opts, err
+		}
+
+		// Check which platform manifests we have blobs for.
+		missingPlatforms := []v1.Platform{}
+		presentPlatforms := []v1.Platform{}
+		for _, child := range children {
+			if containerdimages.IsManifestType(child.MediaType) {
+				_, err := store.ReaderAt(ctx, child)
+				if cerrdefs.IsNotFound(err) {
+					missingPlatforms = append(missingPlatforms, *child.Platform)
+					logrus.WithField("digest", child.Digest.String()).Debug("missing blob, not exporting")
+					continue
+				} else if err != nil {
+					return opts, err
+				}
+				presentPlatforms = append(presentPlatforms, *child.Platform)
+			}
+		}
+
+		// If we have all the manifests, just export the original index.
+		if len(missingPlatforms) == 0 {
+			return append(opts, archive.WithImage(is, img.Name)), nil
+		}
+
+		// Create a new manifest which contains only the manifests we have in store.
+		srcRef := ref.String()
+		targetRef := srcRef + "-tmp-export"
+		newImg, err := converter.Convert(ctx, i.client, targetRef, srcRef,
+			converter.WithPlatform(platforms.Any(presentPlatforms...)))
+		if err != nil {
+			return opts, err
+		}
+		defer i.client.ImageService().Delete(ctx, newImg.Name, containerdimages.SynchronousDelete())
+		return append(opts, archive.WithManifest(newImg.Target, srcRef)), nil
+	}
+
+	return append(opts, archive.WithImage(is, img.Name)), nil
+}