Merge pull request #1431 from ktock/stargz

Enable to pass additional handler on pull for stargz-based remote snapshots

pkg/config/config.go

@@ -73,6 +73,11 @@ type ContainerdConfig struct {
 	// NoPivot disables pivot-root (linux only), required when running a container in a RamDisk with runc
 	// This only works for runtime type "io.containerd.runtime.v1.linux".
 	NoPivot bool `toml:"no_pivot" json:"noPivot"`
+
+	// DisableSnapshotAnnotations disables to pass additional annotations (image
+	// related information) to snapshotters. These annotations are required by
+	// stargz snapshotter (https://github.com/containerd/stargz-snapshotter).
+	DisableSnapshotAnnotations bool `toml:"disable_snapshot_annotations" json:"disableSnapshotAnnotations"`
 }
 
 // CniConfig contains toml config related to cni

pkg/server/image_pull.go

@@ -120,6 +120,10 @@ func (c *criService) PullImage(ctx context.Context, r *runtime.PullImageRequest)
 	}
 
 	pullOpts = append(pullOpts, c.encryptedImagesPullOpts()...)
+	if !c.config.ContainerdConfig.DisableSnapshotAnnotations {
+		pullOpts = append(pullOpts,
+			containerd.WithImageHandlerWrapper(appendInfoHandlerWrapper(ref)))
+	}
 
 	image, err := c.client.Pull(ctx, ref, pullOpts...)
 	if err != nil {
@@ -422,3 +426,42 @@ func (c *criService) encryptedImagesPullOpts() []containerd.RemoteOpt {
 	}
 	return nil
 }
+
+const (
+	// targetRefLabel is a label which contains image reference and will be passed
+	// to snapshotters.
+	targetRefLabel = "containerd.io/snapshot/cri.image-ref"
+	// targetDigestLabel is a label which contains layer digest and will be passed
+	// to snapshotters.
+	targetDigestLabel = "containerd.io/snapshot/cri.layer-digest"
+)
+
+// appendInfoHandlerWrapper makes a handler which appends some basic information
+// of images to each layer descriptor as annotations during unpack. These
+// annotations will be passed to snapshotters as labels. These labels will be
+// used mainly by stargz-based snapshotters for querying image contents from the
+// registry.
+func appendInfoHandlerWrapper(ref string) func(f containerdimages.Handler) containerdimages.Handler {
+	return func(f containerdimages.Handler) containerdimages.Handler {
+		return containerdimages.HandlerFunc(func(ctx context.Context, desc imagespec.Descriptor) ([]imagespec.Descriptor, error) {
+			children, err := f.Handle(ctx, desc)
+			if err != nil {
+				return nil, err
+			}
+			switch desc.MediaType {
+			case imagespec.MediaTypeImageManifest, containerdimages.MediaTypeDockerSchema2Manifest:
+				for i := range children {
+					c := &children[i]
+					if containerdimages.IsLayerType(c.MediaType) {
+						if c.Annotations == nil {
+							c.Annotations = make(map[string]string)
+						}
+						c.Annotations[targetRefLabel] = ref
+						c.Annotations[targetDigestLabel] = c.Digest.String()
+					}
+				}
+			}
+			return children, nil
+		})
+	}
+}