Use "Size" field to describe blobs over "Length"

After consideration, we've changed the main descriptor field name to for number
of bytes to "size" to match convention. While this may be a subjective
argument, commonly we refer to files by their "size" rather than their
"length". This will match other conventions, like `(FileInfo).Size()` and
methods on `io.SizeReaderAt`. Under more broad analysis, this argument doesn't
necessarily hold up. If anything, "size" is shorter than "length".

Signed-off-by: Stephen J Day <stephen.day@docker.com>

blobs.go

@@ -49,8 +49,8 @@ type Descriptor struct {
 	// encoded as utf-8.
 	MediaType string `json:"mediaType,omitempty"`
 
-	// Length in bytes of content.
-	Length int64 `json:"length,omitempty"`
+	// Size in bytes of content.
+	Size int64 `json:"size,omitempty"`
 
 	// Digest uniquely identifies the content. A byte stream can be verified
 	// against against this digest.

docs/notifications.md

@@ -84,8 +84,9 @@ manifest:
    "action": "push",
    "target": {
       "mediaType": "application/vnd.docker.distribution.manifest.v1+json",
-      "length": 1,
+      "size": 1,
       "digest": "sha256:0123456789abcdef0",
+      "length": 1,
       "repository": "library/test",
       "url": "http://example.com/v2/library/test/manifests/latest"
    },
@@ -105,6 +106,11 @@ manifest:
 }
 ```
 
+> __NOTE(stevvooe):__ As of version 2.1, the `length` field for event targets
+> is being deprecated for the `size` field, bringing the target in line with
+> common nomenclature. Both will continue to be set for the foreseeable
+> future. Newer code should favor `size` but accept either.
+
 ## Envelope
 
 The envelope contains one or more events, with the following json structure:

notifications/bridge.go

@@ -97,6 +97,7 @@ func (b *bridge) createManifestEvent(action string, repo string, sm *manifest.Si
 	}
 
 	event.Target.Length = int64(len(p))
+	event.Target.Size = int64(len(p))
 	event.Target.Digest, err = digest.FromBytes(p)
 	if err != nil {
 		return nil, err
@@ -122,6 +123,7 @@ func (b *bridge) createBlobEventAndWrite(action string, repo string, desc distri
 func (b *bridge) createBlobEvent(action string, repo string, desc distribution.Descriptor) (*Event, error) {
 	event := b.createEvent(action)
 	event.Target.Descriptor = desc
+	event.Target.Length = desc.Size
 	event.Target.Repository = repo
 
 	var err error

notifications/event.go

@@ -54,6 +54,10 @@ type Event struct {
 
 		distribution.Descriptor
 
+		// Length in bytes of content. Same as Size field in Descriptor.
+		// Provided for backwards compatibility.
+		Length int64 `json:"length,omitempty"`
+
 		// Repository identifies the named repository.
 		Repository string `json:"repository,omitempty"`
 

notifications/event_test.go

@@ -22,8 +22,9 @@ func TestEventEnvelopeJSONFormat(t *testing.T) {
          "action": "push",
          "target": {
             "mediaType": "application/vnd.docker.distribution.manifest.v1+json",
-            "length": 1,
+            "size": 1,
             "digest": "sha256:0123456789abcdef0",
+            "length": 1,
             "repository": "library/test",
             "url": "http://example.com/v2/library/test/manifests/latest"
          },
@@ -47,8 +48,9 @@ func TestEventEnvelopeJSONFormat(t *testing.T) {
          "action": "push",
          "target": {
             "mediaType": "application/vnd.docker.container.image.rootfs.diff+x-gtar",
-            "length": 2,
+            "size": 2,
             "digest": "tarsum.v2+sha256:0123456789abcdef1",
+            "length": 2,
             "repository": "library/test",
             "url": "http://example.com/v2/library/test/manifests/latest"
          },
@@ -72,8 +74,9 @@ func TestEventEnvelopeJSONFormat(t *testing.T) {
          "action": "push",
          "target": {
             "mediaType": "application/vnd.docker.container.image.rootfs.diff+x-gtar",
-            "length": 3,
+            "size": 3,
             "digest": "tarsum.v2+sha256:0123456789abcdef2",
+            "length": 3,
             "repository": "library/test",
             "url": "http://example.com/v2/library/test/manifests/latest"
          },
@@ -115,7 +118,8 @@ func TestEventEnvelopeJSONFormat(t *testing.T) {
 	manifestPush = prototype
 	manifestPush.ID = "asdf-asdf-asdf-asdf-0"
 	manifestPush.Target.Digest = "sha256:0123456789abcdef0"
-	manifestPush.Target.Length = int64(1)
+	manifestPush.Target.Length = 1
+	manifestPush.Target.Size = 1
 	manifestPush.Target.MediaType = manifest.ManifestMediaType
 	manifestPush.Target.Repository = "library/test"
 	manifestPush.Target.URL = "http://example.com/v2/library/test/manifests/latest"
@@ -125,6 +129,7 @@ func TestEventEnvelopeJSONFormat(t *testing.T) {
 	layerPush0.ID = "asdf-asdf-asdf-asdf-1"
 	layerPush0.Target.Digest = "tarsum.v2+sha256:0123456789abcdef1"
 	layerPush0.Target.Length = 2
+	layerPush0.Target.Size = 2
 	layerPush0.Target.MediaType = layerMediaType
 	layerPush0.Target.Repository = "library/test"
 	layerPush0.Target.URL = "http://example.com/v2/library/test/manifests/latest"
@@ -134,6 +139,7 @@ func TestEventEnvelopeJSONFormat(t *testing.T) {
 	layerPush1.ID = "asdf-asdf-asdf-asdf-2"
 	layerPush1.Target.Digest = "tarsum.v2+sha256:0123456789abcdef2"
 	layerPush1.Target.Length = 3
+	layerPush1.Target.Size = 3
 	layerPush1.Target.MediaType = layerMediaType
 	layerPush1.Target.Repository = "library/test"
 	layerPush1.Target.URL = "http://example.com/v2/library/test/manifests/latest"

registry/client/repository.go

@@ -343,7 +343,7 @@ func (bs *blobs) Open(ctx context.Context, dgst digest.Digest) (distribution.Rea
 		return nil, err
 	}
 
-	return transport.NewHTTPReadSeeker(bs.client, blobURL, stat.Length), nil
+	return transport.NewHTTPReadSeeker(bs.client, blobURL, stat.Size), nil
 }
 
 func (bs *blobs) ServeBlob(ctx context.Context, w http.ResponseWriter, r *http.Request, dgst digest.Digest) error {
@@ -366,7 +366,7 @@ func (bs *blobs) Put(ctx context.Context, mediaType string, p []byte) (distribut
 
 	desc := distribution.Descriptor{
 		MediaType: mediaType,
-		Length:    int64(len(p)),
+		Size:      int64(len(p)),
 		Digest:    dgstr.Digest(),
 	}
 
@@ -435,7 +435,7 @@ func (bs *blobStatter) Stat(ctx context.Context, dgst digest.Digest) (distributi
 
 		return distribution.Descriptor{
 			MediaType: resp.Header.Get("Content-Type"),
-			Length:    length,
+			Size:      length,
 			Digest:    dgst,
 		}, nil
 	case http.StatusNotFound:

registry/client/repository_test.go

@@ -127,8 +127,8 @@ func TestBlobExists(t *testing.T) {
 		t.Fatalf("Unexpected digest: %s, expected %s", stat.Digest, d1)
 	}
 
-	if stat.Length != int64(len(b1)) {
-		t.Fatalf("Unexpected length: %d, expected %d", stat.Length, len(b1))
+	if stat.Size != int64(len(b1)) {
+		t.Fatalf("Unexpected length: %d, expected %d", stat.Size, len(b1))
 	}
 
 	// TODO(dmcgowan): Test error cases and ErrBlobUnknown case
@@ -244,14 +244,14 @@ func TestBlobUploadChunked(t *testing.T) {
 
 	blob, err := upload.Commit(ctx, distribution.Descriptor{
 		Digest: dgst,
-		Length: int64(len(b1)),
+		Size:   int64(len(b1)),
 	})
 	if err != nil {
 		t.Fatal(err)
 	}
 
-	if blob.Length != int64(len(b1)) {
-		t.Fatalf("Unexpected blob size: %d; expected: %d", blob.Length, len(b1))
+	if blob.Size != int64(len(b1)) {
+		t.Fatalf("Unexpected blob size: %d; expected: %d", blob.Size, len(b1))
 	}
 }
 
@@ -352,14 +352,14 @@ func TestBlobUploadMonolithic(t *testing.T) {
 
 	blob, err := upload.Commit(ctx, distribution.Descriptor{
 		Digest: dgst,
-		Length: int64(len(b1)),
+		Size:   int64(len(b1)),
 	})
 	if err != nil {
 		t.Fatal(err)
 	}
 
-	if blob.Length != int64(len(b1)) {
-		t.Fatalf("Unexpected blob size: %d; expected: %d", blob.Length, len(b1))
+	if blob.Size != int64(len(b1)) {
+		t.Fatalf("Unexpected blob size: %d; expected: %d", blob.Size, len(b1))
 	}
 }
 

registry/storage/blob_test.go

@@ -178,7 +178,7 @@ func TestSimpleBlobRead(t *testing.T) {
 		t.Fatalf("error getting seeker size for random layer: %v", err)
 	}
 
-	descBefore := distribution.Descriptor{Digest: dgst, MediaType: "application/octet-stream", Length: randomLayerSize}
+	descBefore := distribution.Descriptor{Digest: dgst, MediaType: "application/octet-stream", Size: randomLayerSize}
 	t.Logf("desc: %v", descBefore)
 
 	desc, err = addBlob(ctx, bs, descBefore, randomLayerReader)
@@ -186,8 +186,8 @@ func TestSimpleBlobRead(t *testing.T) {
 		t.Fatalf("error adding blob to blobservice: %v", err)
 	}
 
-	if desc.Length != randomLayerSize {
-		t.Fatalf("committed blob has incorrect length: %v != %v", desc.Length, randomLayerSize)
+	if desc.Size != randomLayerSize {
+		t.Fatalf("committed blob has incorrect length: %v != %v", desc.Size, randomLayerSize)
 	}
 
 	rc, err = bs.Open(ctx, desc.Digest) // note that we are opening with original digest.
@@ -330,8 +330,8 @@ func addBlob(ctx context.Context, bs distribution.BlobIngester, desc distributio
 
 	if nn, err := io.Copy(wr, rd); err != nil {
 		return distribution.Descriptor{}, err
-	} else if nn != desc.Length {
-		return distribution.Descriptor{}, fmt.Errorf("incorrect number of bytes copied: %v != %v", nn, desc.Length)
+	} else if nn != desc.Size {
+		return distribution.Descriptor{}, fmt.Errorf("incorrect number of bytes copied: %v != %v", nn, desc.Size)
 	}
 
 	return wr.Commit(ctx, desc)

registry/storage/blobserver.go

@@ -41,7 +41,7 @@ func (bs *blobServer) ServeBlob(ctx context.Context, w http.ResponseWriter, r *h
 		http.Redirect(w, r, redirectURL, http.StatusTemporaryRedirect)
 	case driver.ErrUnsupportedMethod:
 		// Fallback to serving the content directly.
-		br, err := newFileReader(ctx, bs.driver, path, desc.Length)
+		br, err := newFileReader(ctx, bs.driver, path, desc.Size)
 		if err != nil {
 			return err
 		}
@@ -61,7 +61,7 @@ func (bs *blobServer) ServeBlob(ctx context.Context, w http.ResponseWriter, r *h
 
 		if w.Header().Get("Content-Length") == "" {
 			// Set the content length if not already set.
-			w.Header().Set("Content-Length", fmt.Sprint(desc.Length))
+			w.Header().Set("Content-Length", fmt.Sprint(desc.Size))
 		}
 
 		http.ServeContent(w, r, desc.Digest.String(), time.Time{}, br)

registry/storage/blobstore.go

@@ -50,7 +50,7 @@ func (bs *blobStore) Open(ctx context.Context, dgst digest.Digest) (distribution
 		return nil, err
 	}
 
-	return newFileReader(ctx, bs.driver, path, desc.Length)
+	return newFileReader(ctx, bs.driver, path, desc.Size)
 }
 
 // Put stores the content p in the blob store, calculating the digest. If the
@@ -81,7 +81,7 @@ func (bs *blobStore) Put(ctx context.Context, mediaType string, p []byte) (distr
 	// TODO(stevvooe): Write out mediatype here, as well.
 
 	return distribution.Descriptor{
-		Length: int64(len(p)),
+		Size: int64(len(p)),
 
 		// NOTE(stevvooe): The central blob store firewalls media types from
 		// other users. The caller should look this up and override the value
@@ -179,7 +179,7 @@ func (bs *blobStatter) Stat(ctx context.Context, dgst digest.Digest) (distributi
 	// mediatype that overrides the main one.
 
 	return distribution.Descriptor{
-		Length: fi.Size(),
+		Size: fi.Size(),
 
 		// NOTE(stevvooe): The central blob store firewalls media types from
 		// other users. The caller should look this up and override the value

registry/storage/blobwriter.go

@@ -148,7 +148,7 @@ func (bw *blobWriter) validateBlob(ctx context.Context, desc distribution.Descri
 			// NOTE(stevvooe): We really don't care if the file is
 			// not actually present for the reader. We now assume
 			// that the desc length is zero.
-			desc.Length = 0
+			desc.Size = 0
 		default:
 			// Any other error we want propagated up the stack.
 			return distribution.Descriptor{}, err
@@ -161,14 +161,14 @@ func (bw *blobWriter) validateBlob(ctx context.Context, desc distribution.Descri
 		bw.size = fi.Size()
 	}
 
-	if desc.Length > 0 {
-		if desc.Length != bw.size {
+	if desc.Size > 0 {
+		if desc.Size != bw.size {
 			return distribution.Descriptor{}, distribution.ErrBlobInvalidLength
 		}
 	} else {
 		// if provided 0 or negative length, we can assume caller doesn't know or
 		// care about length.
-		desc.Length = bw.size
+		desc.Size = bw.size
 	}
 
 	// TODO(stevvooe): This section is very meandering. Need to be broken down
@@ -216,7 +216,7 @@ func (bw *blobWriter) validateBlob(ctx context.Context, desc distribution.Descri
 			}
 
 			// Read the file from the backend driver and validate it.
-			fr, err := newFileReader(ctx, bw.bufferedFileWriter.driver, bw.path, desc.Length)
+			fr, err := newFileReader(ctx, bw.bufferedFileWriter.driver, bw.path, desc.Size)
 			if err != nil {
 				return distribution.Descriptor{}, err
 			}

registry/storage/cache/cache.go

@@ -23,8 +23,8 @@ func ValidateDescriptor(desc distribution.Descriptor) error {
 		return err
 	}
 
-	if desc.Length < 0 {
-		return fmt.Errorf("cache: invalid length in descriptor: %v < 0", desc.Length)
+	if desc.Size < 0 {
+		return fmt.Errorf("cache: invalid length in descriptor: %v < 0", desc.Size)
 	}
 
 	if desc.MediaType == "" {

registry/storage/cache/redis/redis.go

@@ -66,17 +66,20 @@ func (rbds *redisBlobDescriptorService) Stat(ctx context.Context, dgst digest.Di
 // stat provides an internal stat call that takes a connection parameter. This
 // allows some internal management of the connection scope.
 func (rbds *redisBlobDescriptorService) stat(ctx context.Context, conn redis.Conn, dgst digest.Digest) (distribution.Descriptor, error) {
-	reply, err := redis.Values(conn.Do("HMGET", rbds.blobDescriptorHashKey(dgst), "digest", "length", "mediatype"))
+	reply, err := redis.Values(conn.Do("HMGET", rbds.blobDescriptorHashKey(dgst), "digest", "size", "mediatype"))
 	if err != nil {
 		return distribution.Descriptor{}, err
 	}
 
-	if len(reply) < 2 || reply[0] == nil || reply[1] == nil { // don't care if mediatype is nil
+	// NOTE(stevvooe): The "size" field used to be "length". We treat a
+	// missing "size" field here as an unknown blob, which causes a cache
+	// miss, effectively migrating the field.
+	if len(reply) < 3 || reply[0] == nil || reply[1] == nil { // don't care if mediatype is nil
 		return distribution.Descriptor{}, distribution.ErrBlobUnknown
 	}
 
 	var desc distribution.Descriptor
-	if _, err := redis.Scan(reply, &desc.Digest, &desc.Length, &desc.MediaType); err != nil {
+	if _, err := redis.Scan(reply, &desc.Digest, &desc.Size, &desc.MediaType); err != nil {
 		return distribution.Descriptor{}, err
 	}
 
@@ -104,7 +107,7 @@ func (rbds *redisBlobDescriptorService) SetDescriptor(ctx context.Context, dgst
 func (rbds *redisBlobDescriptorService) setDescriptor(ctx context.Context, conn redis.Conn, dgst digest.Digest, desc distribution.Descriptor) error {
 	if _, err := conn.Do("HMSET", rbds.blobDescriptorHashKey(dgst),
 		"digest", desc.Digest,
-		"length", desc.Length); err != nil {
+		"size", desc.Size); err != nil {
 		return err
 	}
 

registry/storage/cache/suite.go

@@ -35,14 +35,14 @@ func checkBlobDescriptorCacheEmptyRepository(t *testing.T, ctx context.Context,
 
 	if err := cache.SetDescriptor(ctx, "", distribution.Descriptor{
 		Digest:    "sha384:abc",
-		Length:    10,
+		Size:      10,
 		MediaType: "application/octet-stream"}); err != digest.ErrDigestInvalidFormat {
 		t.Fatalf("expected error with invalid digest: %v", err)
 	}
 
 	if err := cache.SetDescriptor(ctx, "sha384:abc", distribution.Descriptor{
 		Digest:    "",
-		Length:    10,
+		Size:      10,
 		MediaType: "application/octet-stream"}); err == nil {
 		t.Fatalf("expected error setting value on invalid descriptor")
 	}
@@ -60,7 +60,7 @@ func checkBlobDescriptorCacheSetAndRead(t *testing.T, ctx context.Context, provi
 	localDigest := digest.Digest("sha384:abc")
 	expected := distribution.Descriptor{
 		Digest:    "sha256:abc",
-		Length:    10,
+		Size:      10,
 		MediaType: "application/octet-stream"}
 
 	cache, err := provider.RepositoryScoped("foo/bar")