Fix image size calculation in importer

After upgrading docker/distibution V1Compatibility no longer contains Size. For
this reason, the image size calculation is wrong. A new way to calculate the
size repeats the way that dockerregistry calculates the size.

pkg/image/api/helper.go

@@ -363,6 +363,8 @@ func ImageWithMetadata(image *Image) error {
 			image.DockerImageLayers[i].Name = layer.DockerBlobSum
 		}
 		if len(manifest.History) == len(image.DockerImageLayers) {
+			// This code does not work since hub.docker.com has been updated.
+			// The V1Compatibility no longer contains Size.
 			image.DockerImageLayers[0].Size = v1Metadata.Size
 			var size = DockerV1CompatibilityImageSize{}
 			for i, obj := range manifest.History[1:] {

pkg/image/importer/importer.go

@@ -282,6 +282,27 @@ func applyErrorToRepository(repository *importRepository, err error) {
 	}
 }
 
+func calculateImageSize(ctx gocontext.Context, repo distribution.Repository, image *api.Image) error {
+	bs := repo.Blobs(ctx)
+
+	layerSet := sets.NewString()
+	size := int64(0)
+	for i := range image.DockerImageLayers {
+		layer := &image.DockerImageLayers[i]
+		desc, err := bs.Stat(ctx, digest.Digest(layer.Name))
+		if err != nil {
+			return err
+		}
+		layer.Size = desc.Size
+		if !layerSet.Has(layer.Name) {
+			size += desc.Size
+			layerSet.Insert(layer.Name)
+		}
+	}
+	image.DockerImageMetadata.Size = size
+	return nil
+}
+
 // importRepositoryFromDocker loads the tags and images requested in the passed importRepository, obeying the
 // optional rate limiter.  Errors are set onto the individual tags and digest objects.
 func importRepositoryFromDocker(ctx gocontext.Context, retriever RepositoryRetriever, repository *importRepository, limiter flowcontrol.RateLimiter) {
@@ -397,6 +418,12 @@ func importRepositoryFromDocker(ctx gocontext.Context, retriever RepositoryRetri
 			importDigest.Err = err
 			continue
 		}
+		if importDigest.Image.DockerImageMetadata.Size == 0 {
+			if err := calculateImageSize(ctx, repo, importDigest.Image); err != nil {
+				importDigest.Err = err
+				continue
+			}
+		}
 	}
 
 	for i := range repository.Tags {
@@ -430,6 +457,12 @@ func importRepositoryFromDocker(ctx gocontext.Context, retriever RepositoryRetri
 			importTag.Err = err
 			continue
 		}
+		if importTag.Image.DockerImageMetadata.Size == 0 {
+			if err := calculateImageSize(ctx, repo, importTag.Image); err != nil {
+				importTag.Err = err
+				continue
+			}
+		}
 	}
 }