Avoid parsing image metadata

Avoid parsing metadata that the image library keeps in order to find an
image's top layer and creation date; instead, use the values which the
storage library now makes available, which will be correct once we merge
PR #654 or something like it.

Instead of assuming the last blob which was added for the image was the
manifest, read it directly and compute its digest ourselves.

Signed-off-by: Nalin Dahyabhai <nalin@redhat.com>

cmd/kpod/images.go

@@ -6,8 +6,8 @@ import (
 	"text/template"
 
 	"github.com/containers/storage"
-	"github.com/kubernetes-incubator/cri-o/libkpod/image"
 	libkpodimage "github.com/kubernetes-incubator/cri-o/libkpod/image"
+	digest "github.com/opencontainers/go-digest"
 	"github.com/pkg/errors"
 	"github.com/urfave/cli"
 )
@@ -15,7 +15,7 @@ import (
 type imageOutputParams struct {
 	ID        string
 	Name      string
-	Digest    string
+	Digest    digest.Digest
 	CreatedAt string
 	Size      string
 }
@@ -132,16 +132,14 @@ func outputHeader(truncate, digests bool) {
 
 func outputImages(store storage.Store, images []storage.Image, format string, hasTemplate, truncate, digests, quiet bool) error {
 	for _, img := range images {
-		imageMetadata, err := image.ParseMetadata(img)
+		createdTime := img.Created.Format("Jan 2, 2006 15:04")
-		if err != nil {
+
-			fmt.Println(err)
+		name := ""
+		if len(img.Names) > 0 {
+			name = img.Names[0]
 		}
-		createdTime := imageMetadata.CreatedTime.Format("Jan 2, 2006 15:04")
+
-		digest := ""
+		digest, size, _ := libkpodimage.DigestAndSize(store, img)
-		if len(imageMetadata.Blobs) > 0 {
-			digest = string(imageMetadata.Blobs[0].Digest)
-		}
-		size, _ := libkpodimage.Size(store, img)
 
 		if quiet {
 			fmt.Printf("%-64s\n", img.ID)
@@ -151,14 +149,13 @@ func outputImages(store storage.Store, images []storage.Image, format string, ha
 
 		params := imageOutputParams{
 			ID:        img.ID,
-			Name:      img.Names[0],
+			Name:      name,
 			Digest:    digest,
 			CreatedAt: createdTime,
 			Size:      libkpodimage.FormattedSize(size),
 		}
 		if hasTemplate {
-			err = outputUsingTemplate(format, params)
+			if err := outputUsingTemplate(format, params); err != nil {
-			if err != nil {
 				return err
 			}
 			continue

libkpod/image/image.go

@@ -8,6 +8,7 @@ import (
 	is "github.com/containers/image/storage"
 	"github.com/containers/storage"
 	"github.com/kubernetes-incubator/cri-o/libkpod/common"
+	digest "github.com/opencontainers/go-digest"
 	"github.com/pkg/errors"
 )
 
@@ -41,13 +42,13 @@ func ParseFilter(store storage.Store, filter string) (*FilterParams, error) {
 			params.label = pair[1]
 		case "before":
 			if img, err := findImageInSlice(images, pair[1]); err == nil {
-				params.beforeImage, _ = getCreatedTime(img)
+				params.beforeImage = img.Created
 			} else {
 				return nil, fmt.Errorf("no such id: %s", pair[0])
 			}
 		case "since":
 			if img, err := findImageInSlice(images, pair[1]); err == nil {
-				params.sinceImage, _ = getCreatedTime(img)
+				params.sinceImage = img.Created
 			} else {
 				return nil, fmt.Errorf("no such id: %s``", pair[0])
 			}
@@ -123,11 +124,7 @@ func matchesBeforeImage(image storage.Image, name string, params *FilterParams)
 	if params.beforeImage.IsZero() {
 		return true
 	}
-	createdTime, err := getCreatedTime(image)
+	if image.Created.Before(params.beforeImage) {
-	if err != nil {
-		return false
-	}
-	if createdTime.Before(params.beforeImage) {
 		return true
 	}
 	return false
@@ -139,11 +136,7 @@ func matchesSinceImage(image storage.Image, name string, params *FilterParams) b
 	if params.sinceImage.IsZero() {
 		return true
 	}
-	createdTime, err := getCreatedTime(image)
+	if image.Created.After(params.sinceImage) {
-	if err != nil {
-		return false
-	}
-	if createdTime.After(params.beforeImage) {
 		return true
 	}
 	return false
@@ -219,43 +212,32 @@ func findImageInSlice(images []storage.Image, ref string) (storage.Image, error)
 	return storage.Image{}, errors.New("could not find image")
 }
 
-// Size returns the size of the image in the given store
+// DigestAndSize returns the size of the image in the given store and the
-func Size(store storage.Store, img storage.Image) (int64, error) {
+// digest of its manifest, if it has one, or "" if it doesn't.
+func DigestAndSize(store storage.Store, img storage.Image) (digest.Digest, int64, error) {
 	is.Transport.SetStore(store)
 	storeRef, err := is.Transport.ParseStoreReference(store, "@"+img.ID)
 	if err != nil {
-		return -1, err
+		return "", -1, errors.Wrapf(err, "error parsing image reference %q", "@"+img.ID)
 	}
 	imgRef, err := storeRef.NewImage(nil)
 	if err != nil {
-		return -1, err
+		return "", -1, errors.Wrapf(err, "error reading image %q", img.ID)
 	}
 	defer imgRef.Close()
 	imgSize, err := imgRef.Size()
 	if err != nil {
-		return -1, err
+		return "", -1, errors.Wrapf(err, "error reading size of image %q", img.ID)
 	}
-	return imgSize, nil
+	manifest, _, err := imgRef.Manifest()
-}
-
-// GetTopLayerID returns the ID of the top layer of the image
-func GetTopLayerID(img storage.Image) (string, error) {
-	metadata, err := ParseMetadata(img)
 	if err != nil {
-		return "", err
+		return "", -1, errors.Wrapf(err, "error reading manifest for image %q", img.ID)
 	}
-	// Get the digest of the first blob
+	manifestDigest := digest.Digest("")
-	digest := string(metadata.Blobs[0].Digest)
+	if len(manifest) > 0 {
-	// Return the first layer associated with the given digest
+		manifestDigest = digest.Canonical.FromBytes(manifest)
-	return metadata.Layers[digest][0], nil
-}
-
-func getCreatedTime(image storage.Image) (time.Time, error) {
-	metadata, err := ParseMetadata(image)
-	if err != nil {
-		return time.Time{}, err
 	}
-	return metadata.CreatedTime, nil
+	return manifestDigest, imgSize, nil
 }
 
 // GetImagesMatchingFilter returns a slice of all images in the store that match the provided FilterParams.

libkpod/image/imageData.go

@@ -7,6 +7,7 @@ import (
 	"github.com/containers/storage"
 	"github.com/kubernetes-incubator/cri-o/cmd/kpod/docker"
 	"github.com/kubernetes-incubator/cri-o/libkpod/driver"
+	digest "github.com/opencontainers/go-digest"
 	ociv1 "github.com/opencontainers/image-spec/specs-go/v1"
 	"github.com/pkg/errors"
 )
@@ -17,6 +18,7 @@ type ImageData struct {
 	ID              string
 	Tags            []string
 	Digests         []string
+	Digest          digest.Digest
 	Parent          string
 	Comment         string
 	Created         *time.Time
@@ -32,11 +34,6 @@ type ImageData struct {
 	RootFS          ociv1.RootFS
 }
 
-type rootFS struct {
-	Type   string
-	Layers []string
-}
-
 // ParseImageNames parses the names we've stored with an image into a list of
 // tagged references and a list of references which contain digests.
 func ParseImageNames(names []string) (tags, digests []string, err error) {
@@ -85,10 +82,7 @@ func GetImageData(store storage.Store, name string) (*ImageData, error) {
 		return nil, err
 	}
 
-	topLayerID, err := GetTopLayerID(*img)
+	topLayerID := img.TopLayer
-	if err != nil {
-		return nil, err
-	}
 
 	driverMetadata, err := driver.GetDriverMetadata(store, topLayerID)
 	if err != nil {
@@ -104,7 +98,7 @@ func GetImageData(store storage.Store, name string) (*ImageData, error) {
 		return nil, err
 	}
 
-	virtualSize, err := Size(store, *img)
+	digest, virtualSize, err := DigestAndSize(store, *img)
 	if err != nil {
 		return nil, err
 	}
@@ -113,6 +107,7 @@ func GetImageData(store storage.Store, name string) (*ImageData, error) {
 		ID:              img.ID,
 		Tags:            tags,
 		Digests:         digests,
+		Digest:          digest,
 		Parent:          string(cid.Docker.Parent),
 		Comment:         cid.OCIv1.History[0].Comment,
 		Created:         cid.OCIv1.Created,

libkpod/image/metadata.go

@@ -1,32 +0,0 @@
-package image
-
-import (
-	"encoding/json"
-	"strings"
-	"time"
-
-	"github.com/containers/image/types"
-	"github.com/containers/storage"
-)
-
-// Metadata stores all of the metadata for an image
-type Metadata struct {
-	Tag            string              `json:"tag"`
-	CreatedTime    time.Time           `json:"created-time"`
-	ID             string              `json:"id"`
-	Blobs          []types.BlobInfo    `json:"blob-list"`
-	Layers         map[string][]string `json:"layers"`
-	SignatureSizes []string            `json:"signature-sizes"`
-}
-
-// ParseMetadata takes an image, parses the json stored in it's metadata
-// field, and converts it to a Metadata struct
-func ParseMetadata(image storage.Image) (Metadata, error) {
-	var m Metadata
-
-	dec := json.NewDecoder(strings.NewReader(image.Metadata))
-	if err := dec.Decode(&m); err != nil {
-		return Metadata{}, err
-	}
-	return m, nil
-}