Merge pull request #4414 from dmcgowan/discard-content

Set content labels based on content type

images/handlers.go

@@ -170,6 +170,19 @@ func ChildrenHandler(provider content.Provider) HandlerFunc {
 // 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 SetChildrenMappedLabels(manager, f, nil)
+}
+
+// SetChildrenMappedLabels 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.
+// The label map allows the caller to control the labels per child descriptor.
+// For returned labels, the index of the child will be appended to the end
+// except for the first index when the returned label does not end with '.'.
+func SetChildrenMappedLabels(manager content.Manager, f HandlerFunc, labelMap func(ocispec.Descriptor) []string) HandlerFunc {
+	if labelMap == nil {
+		labelMap = ChildGCLabels
+	}
 	return func(ctx context.Context, desc ocispec.Descriptor) ([]ocispec.Descriptor, error) {
 		children, err := f(ctx, desc)
 		if err != nil {
@@ -177,14 +190,26 @@ func SetChildrenLabels(manager content.Manager, f HandlerFunc) HandlerFunc {
 		}
 
 		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))
+			var (
+				info = content.Info{
+					Digest: desc.Digest,
+					Labels: map[string]string{},
+				}
+				fields = []string{}
+				keys   = map[string]uint{}
+			)
+			for _, ch := range children {
+				labelKeys := labelMap(ch)
+				for _, key := range labelKeys {
+					idx := keys[key]
+					keys[key] = idx + 1
+					if idx > 0 || key[len(key)-1] == '.' {
+						key = fmt.Sprintf("%s%d", key, idx)
+					}
+
+					info.Labels[key] = ch.Digest.String()
+					fields = append(fields, "labels."+key)
+				}
 			}
 
 			_, err := manager.Update(ctx, info, fields...)

images/mediatypes.go

@@ -125,3 +125,31 @@ func IsKnownConfig(mt string) bool {
 	}
 	return false
 }
+
+// ChildGCLabels returns the label for a given descriptor to reference it
+func ChildGCLabels(desc ocispec.Descriptor) []string {
+	mt := desc.MediaType
+	if IsKnownConfig(mt) {
+		return []string{"containerd.io/gc.ref.content.config"}
+	}
+
+	switch mt {
+	case MediaTypeDockerSchema2Manifest, ocispec.MediaTypeImageManifest:
+		return []string{"containerd.io/gc.ref.content.m."}
+	}
+
+	if IsLayerType(mt) {
+		return []string{"containerd.io/gc.ref.content.l."}
+	}
+
+	return []string{"containerd.io/gc.ref.content."}
+}
+
+// ChildGCLabelsFilterLayers returns the labels for a given descriptor to
+// reference it, skipping layer media types
+func ChildGCLabelsFilterLayers(desc ocispec.Descriptor) []string {
+	if IsLayerType(desc.MediaType) {
+		return nil
+	}
+	return ChildGCLabels(desc)
+}