Update fetch handling

Fix issue where manifest content must always be fetched
even if it is already fully downloaded or shared locally.
Simplify children label setting and platform filtering.
Prevent getting a fetcher when content shared locally.

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

images/handlers.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 
 	"github.com/containerd/containerd/content"
+	"github.com/containerd/containerd/platforms"
 	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
 	"github.com/pkg/errors"
 	"golang.org/x/sync/errgroup"
@@ -128,8 +129,78 @@ func Dispatch(ctx context.Context, handler Handler, descs ...ocispec.Descriptor)
 //
 // One can also replace this with another implementation to allow descending of
 // arbitrary types.
-func ChildrenHandler(provider content.Provider, platform string) HandlerFunc {
+func ChildrenHandler(provider content.Provider) HandlerFunc {
 	return func(ctx context.Context, desc ocispec.Descriptor) ([]ocispec.Descriptor, error) {
-		return Children(ctx, provider, desc, platform)
+		return Children(ctx, provider, desc)
+	}
+}
+
+// SetChildrenLabels is a handler wrapper which sets labels for the content on
+// the children returned by the handler and passes through the children.
+// Must follow a handler that returns the children to be labeled.
+func SetChildrenLabels(manager content.Manager, f HandlerFunc) HandlerFunc {
+	return func(ctx context.Context, desc ocispec.Descriptor) ([]ocispec.Descriptor, error) {
+		children, err := f(ctx, desc)
+		if err != nil {
+			return children, err
+		}
+
+		if len(children) > 0 {
+			info := content.Info{
+				Digest: desc.Digest,
+				Labels: map[string]string{},
+			}
+			fields := []string{}
+			for i, ch := range children {
+				info.Labels[fmt.Sprintf("containerd.io/gc.ref.content.%d", i)] = ch.Digest.String()
+				fields = append(fields, fmt.Sprintf("labels.containerd.io/gc.ref.content.%d", i))
+			}
+
+			_, err := manager.Update(ctx, info, fields...)
+			if err != nil {
+				return nil, err
+			}
+		}
+
+		return children, err
+	}
+}
+
+// FilterPlatform is a handler wrapper which limits the descriptors returned
+// by a handler to a single platform.
+func FilterPlatform(platform string, f HandlerFunc) HandlerFunc {
+	return func(ctx context.Context, desc ocispec.Descriptor) ([]ocispec.Descriptor, error) {
+		children, err := f(ctx, desc)
+		if err != nil {
+			return children, err
+		}
+
+		var descs []ocispec.Descriptor
+		if platform != "" && isMultiPlatform(desc.MediaType) {
+			matcher, err := platforms.Parse(platform)
+			if err != nil {
+				return nil, err
+			}
+
+			for _, d := range children {
+				if d.Platform == nil || matcher.Match(*d.Platform) {
+					descs = append(descs, d)
+				}
+			}
+		} else {
+			descs = children
+		}
+
+		return descs, nil
+	}
+
+}
+
+func isMultiPlatform(mediaType string) bool {
+	switch mediaType {
+	case MediaTypeDockerSchema2ManifestList, ocispec.MediaTypeImageIndex:
+		return true
+	default:
+		return false
 	}
 }

images/image.go

@@ -102,7 +102,7 @@ func (image *Image) Size(ctx context.Context, provider content.Provider, platfor
 		}
 		size += desc.Size
 		return nil, nil
-	}), ChildrenHandler(provider, platform)), image.Target)
+	}), FilterPlatform(platform, ChildrenHandler(provider))), image.Target)
 }
 
 // Manifest resolves a manifest from the image for the given platform.
@@ -238,7 +238,7 @@ func Platforms(ctx context.Context, provider content.Provider, image ocispec.Des
 				platforms.Normalize(ocispec.Platform{OS: image.OS, Architecture: image.Architecture}))
 		}
 		return nil, nil
-	}), ChildrenHandler(provider, "")), image)
+	}), ChildrenHandler(provider)), image)
 }
 
 // Check returns nil if the all components of an image are available in the
@@ -285,7 +285,7 @@ func Check(ctx context.Context, provider content.Provider, image ocispec.Descrip
 }
 
 // Children returns the immediate children of content described by the descriptor.
-func Children(ctx context.Context, provider content.Provider, desc ocispec.Descriptor, platform string) ([]ocispec.Descriptor, error) {
+func Children(ctx context.Context, provider content.Provider, desc ocispec.Descriptor) ([]ocispec.Descriptor, error) {
 	var descs []ocispec.Descriptor
 	switch desc.MediaType {
 	case MediaTypeDockerSchema2Manifest, ocispec.MediaTypeImageManifest:
@@ -314,21 +314,7 @@ func Children(ctx context.Context, provider content.Provider, desc ocispec.Descr
 			return nil, err
 		}
 
-		if platform != "" {
-			matcher, err := platforms.Parse(platform)
-			if err != nil {
-				return nil, err
-			}
-
-			for _, d := range index.Manifests {
-				if d.Platform == nil || matcher.Match(*d.Platform) {
-					descs = append(descs, d)
-				}
-			}
-		} else {
-			descs = append(descs, index.Manifests...)
-		}
-
+		descs = append(descs, index.Manifests...)
 	case MediaTypeDockerSchema2Layer, MediaTypeDockerSchema2LayerGzip,
 		MediaTypeDockerSchema2LayerForeign, MediaTypeDockerSchema2LayerForeignGzip,
 		MediaTypeDockerSchema2Config, ocispec.MediaTypeImageConfig,

images/oci/exporter.go

@@ -42,7 +42,7 @@ func (oe *V1Exporter) Export(ctx context.Context, store content.Store, desc ocis
 	}
 
 	handlers := images.Handlers(
-		images.ChildrenHandler(store, platforms.Default()),
+		images.FilterPlatform(platforms.Default(), images.ChildrenHandler(store)),
 		images.HandlerFunc(exportHandler),
 	)