Function applyLayer

daemon/pkg/plugin/fetch_linux.go:120–149

applyLayer makes an c8dimages.HandlerFunc which applies a fetched image rootfs layer to a directory. TODO(@cpuguy83) This gets run sequentially after layer pull (makes sense), however if there are multiple layers to fetch we may end up extracting layers in the wrong order.

(cs content.Store, dir string, out progress.Output)

// if there are multiple layers to fetch we may end up extracting layers in the wrong
// order.
func applyLayer(cs content.Store, dir string, out progress.Output) c8dimages.HandlerFunc {
	return func(ctx context.Context, desc ocispec.Descriptor) ([]ocispec.Descriptor, error) {
		switch desc.MediaType {
		case
			ocispec.MediaTypeImageLayer,
			c8dimages.MediaTypeDockerSchema2Layer,
			ocispec.MediaTypeImageLayerGzip,
			c8dimages.MediaTypeDockerSchema2LayerGzip:
		default:
			return nil, nil
		}

		ra, err := cs.ReaderAt(ctx, desc)
		if err != nil {
			return nil, errors.Wrapf(err, "error getting content from content store for digest %s", desc.Digest)
		}

		id := stringid.TruncateID(desc.Digest.String())

		rc := ioutils.NewReadCloserWrapper(content.NewReader(ra), ra.Close)
		pr := progress.NewProgressReader(rc, out, desc.Size, id, "Extracting")
		defer pr.Close()

		if _, err := chrootarchive.ApplyLayer(dir, pr); err != nil {
			return nil, errors.Wrapf(err, "error applying layer for digest %s", desc.Digest)
		}
		progress.Update(out, id, "Complete")
		return nil, nil
	}
}

func childrenHandler(cs content.Store) c8dimages.HandlerFunc {
	ch := c8dimages.ChildrenHandler(cs)