pkg/image: conditionally parse raw image manifest

the Image REST strategy logs errors when it cannot parse the raw json
manifest when creating an Image object. however, this is not an error,
as a call to this api might have already cleared the DockerImageManifest
from the Image object.

Author: flavianmissi

pkg/image/apiserver/registry/image/strategy.go

@@ -52,28 +52,40 @@ func (s imageStrategy) PrepareForCreate(ctx context.Context, obj runtime.Object)
 		utilruntime.HandleError(fmt.Errorf("unable to update image metadata for %q: %v", newImage.Name, err))
 	}
 
-	manifest, _, err := distribution.UnmarshalManifest(
-		newImage.DockerImageManifestMediaType,
-		[]byte(newImage.DockerImageManifest),
-	)
-	if err != nil {
-		utilruntime.HandleError(fmt.Errorf("unable to parse manifest for %q: %v", newImage.Name, err))
-	}
+	// initially, the code in this function did not account for these
+	// different contexts.
+	// the code in this function is called from two contexts:
+	//   1. image stream imports, which are also triggered by creating image
+	//      streams and adding tags to them;
+	//   2. direct pushes to the internal registry, i.e. podman push
+	// on 1. the raw manifest json is cleared from image.DockerImageManifest
+	// to avoid unbound growth of Image objects in etcd; and on 2. the raw
+	// manifest json is still set in the image.DockerImageManifest.
+	// the code block below should not cause side effects on either path.
+	if len(newImage.DockerImageManifest) != 0 {
+		manifest, _, err := distribution.UnmarshalManifest(
+			newImage.DockerImageManifestMediaType,
+			[]byte(newImage.DockerImageManifest),
+		)
+		if err != nil {
+			utilruntime.HandleError(fmt.Errorf("unable to parse manifest for %q: %v", newImage.Name, err))
+		}
 
-	if mlist, ok := manifest.(*manifestlist.DeserializedManifestList); ok {
-		subManifests := []imageapi.ImageManifest{}
-		for _, m := range mlist.Manifests {
-			im := imageapi.ImageManifest{
-				Digest:       m.Digest.String(),
-				MediaType:    m.MediaType,
-				ManifestSize: m.Size,
-				Architecture: m.Platform.Architecture,
-				OS:           m.Platform.OS,
-				Variant:      m.Platform.Variant,
+		if mlist, ok := manifest.(*manifestlist.DeserializedManifestList); ok {
+			subManifests := []imageapi.ImageManifest{}
+			for _, m := range mlist.Manifests {
+				im := imageapi.ImageManifest{
+					Digest:       m.Digest.String(),
+					MediaType:    m.MediaType,
+					ManifestSize: m.Size,
+					Architecture: m.Platform.Architecture,
+					OS:           m.Platform.OS,
+					Variant:      m.Platform.Variant,
+				}
+				subManifests = append(subManifests, im)
 			}
-			subManifests = append(subManifests, im)
+			newImage.DockerImageManifests = subManifests
 		}
-		newImage.DockerImageManifests = subManifests
 	}
 
 	if newImage.Annotations[imagev1.ImageManifestBlobStoredAnnotation] == "true" {