7 files changed, 34 insertions, 13 deletions
diff --git a/tools/nixery/builder/builder.go b/tools/nixery/builder/builder.go
index 028bcc57690a..115f1e37ef32 100644
--- a/tools/nixery/builder/builder.go
+++ b/tools/nixery/builder/builder.go
@@ -420,7 +420,7 @@ func (b *byteCounter) Write(p []byte) (n int, err error) {
 // image manifest.
 func uploadHashLayer(ctx context.Context, s *State, key string, lw layerWriter) (*manifest.Entry, error) {
 	path := "staging/" + key
-	sha256sum, size, err := s.Storage.Persist(ctx, path, func(sw io.Writer) (string, int64, error) {
+	sha256sum, size, err := s.Storage.Persist(ctx, path, manifest.LayerType, func(sw io.Writer) (string, int64, error) {
 		// Sets up a "multiwriter" that simultaneously runs both hash
 		// algorithms and uploads to the storage backend.
 		shasum := sha256.New()
diff --git a/tools/nixery/builder/cache.go b/tools/nixery/builder/cache.go
index a4ebe03e1c94..35b563e52496 100644
--- a/tools/nixery/builder/cache.go
+++ b/tools/nixery/builder/cache.go
@@ -152,7 +152,7 @@ func cacheManifest(ctx context.Context, s *State, key string, m json.RawMessage)
 	go s.Cache.localCacheManifest(key, m)
 
 	path := "manifests/" + key
-	_, size, err := s.Storage.Persist(ctx, path, func(w io.Writer) (string, int64, error) {
+	_, size, err := s.Storage.Persist(ctx, path, manifest.ManifestType, func(w io.Writer) (string, int64, error) {
 		size, err := io.Copy(w, bytes.NewReader([]byte(m)))
 		return "", size, err
 	})
@@ -220,7 +220,7 @@ func cacheLayer(ctx context.Context, s *State, key string, entry manifest.Entry)
 
 	j, _ := json.Marshal(&entry)
 	path := "builds/" + key
-	_, _, err := s.Storage.Persist(ctx, path, func(w io.Writer) (string, int64, error) {
+	_, _, err := s.Storage.Persist(ctx, path, "", func(w io.Writer) (string, int64, error) {
 		size, err := io.Copy(w, bytes.NewReader(j))
 		return "", size, err
 	})
diff --git a/tools/nixery/main.go b/tools/nixery/main.go
index 39cfbc525528..d94d51b4681e 100644
--- a/tools/nixery/main.go
+++ b/tools/nixery/main.go
@@ -38,6 +38,7 @@ import (
 	"github.com/google/nixery/builder"
 	"github.com/google/nixery/config"
 	"github.com/google/nixery/logs"
+	mf "github.com/google/nixery/manifest"
 	"github.com/google/nixery/storage"
 	log "github.com/sirupsen/logrus"
 )
@@ -170,7 +171,7 @@ func (h *registryHandler) serveManifestTag(w http.ResponseWriter, r *http.Reques
 	path := "layers/" + sha256sum
 	ctx := context.TODO()
 
-	_, _, err = h.state.Storage.Persist(ctx, path, func(sw io.Writer) (string, int64, error) {
+	_, _, err = h.state.Storage.Persist(ctx, path, mf.ManifestType, func(sw io.Writer) (string, int64, error) {
 		// We already know the hash, so no additional hash needs to be
 		// constructed here.
 		written, err := sw.Write(manifest)
diff --git a/tools/nixery/manifest/manifest.go b/tools/nixery/manifest/manifest.go
index 0d36826fb7e5..e499920075f0 100644
--- a/tools/nixery/manifest/manifest.go
+++ b/tools/nixery/manifest/manifest.go
@@ -28,8 +28,8 @@ const (
 	schemaVersion = 2
 
 	// media types
-	manifestType = "application/vnd.docker.distribution.manifest.v2+json"
-	layerType    = "application/vnd.docker.image.rootfs.diff.tar.gzip"
+	ManifestType = "application/vnd.docker.distribution.manifest.v2+json"
+	LayerType    = "application/vnd.docker.image.rootfs.diff.tar.gzip"
 	configType   = "application/vnd.docker.container.image.v1+json"
 
 	// image config constants
@@ -117,7 +117,7 @@ func Manifest(arch string, layers []Entry) (json.RawMessage, ConfigLayer) {
 	hashes := make([]string, len(layers))
 	for i, l := range layers {
 		hashes[i] = l.TarHash
-		l.MediaType = layerType
+		l.MediaType = LayerType
 		l.TarHash = ""
 		layers[i] = l
 	}
@@ -126,7 +126,7 @@ func Manifest(arch string, layers []Entry) (json.RawMessage, ConfigLayer) {
 
 	m := manifest{
 		SchemaVersion: schemaVersion,
-		MediaType:     manifestType,
+		MediaType:     ManifestType,
 		Config: Entry{
 			MediaType: configType,
 			Size:      int64(len(c.Config)),
diff --git a/tools/nixery/storage/filesystem.go b/tools/nixery/storage/filesystem.go
index 926e9257a1e0..bd757587b4db 100644
--- a/tools/nixery/storage/filesystem.go
+++ b/tools/nixery/storage/filesystem.go
@@ -49,7 +49,8 @@ func (b *FSBackend) Name() string {
 	return fmt.Sprintf("Filesystem (%s)", b.path)
 }
 
-func (b *FSBackend) Persist(ctx context.Context, key string, f Persister) (string, int64, error) {
+// TODO(tazjin): Implement support for persisting content-types for the filesystem backend.
+func (b *FSBackend) Persist(ctx context.Context, key, _type string, f Persister) (string, int64, error) {
 	full := path.Join(b.path, key)
 	dir := path.Dir(full)
 	err := os.MkdirAll(dir, 0755)
diff --git a/tools/nixery/storage/gcs.go b/tools/nixery/storage/gcs.go
index 61b5dea52351..eac34461af76 100644
--- a/tools/nixery/storage/gcs.go
+++ b/tools/nixery/storage/gcs.go
@@ -80,17 +80,36 @@ func (b *GCSBackend) Name() string {
 	return "Google Cloud Storage (" + b.bucket + ")"
 }
 
-func (b *GCSBackend) Persist(ctx context.Context, path string, f Persister) (string, int64, error) {
+func (b *GCSBackend) Persist(ctx context.Context, path, contentType string, f Persister) (string, int64, error) {
 	obj := b.handle.Object(path)
 	w := obj.NewWriter(ctx)
 
 	hash, size, err := f(w)
 	if err != nil {
-		log.WithError(err).WithField("path", path).Error("failed to upload to GCS")
+		log.WithError(err).WithField("path", path).Error("failed to write to GCS")
 		return hash, size, err
 	}
 
-	return hash, size, w.Close()
+	err = w.Close()
+	if err != nil {
+		log.WithError(err).WithField("path", path).Error("failed to complete GCS upload")
+		return hash, size, err
+	}
+
+	// GCS natively supports content types for objects, which will be
+	// used when serving them back.
+	if contentType != "" {
+		_, err = obj.Update(ctx, storage.ObjectAttrsToUpdate{
+			ContentType: contentType,
+		})
+
+		if err != nil {
+			log.WithError(err).WithField("path", path).Error("failed to update object attrs")
+			return hash, size, err
+		}
+	}
+
+	return hash, size, nil
 }
 
 func (b *GCSBackend) Fetch(ctx context.Context, path string) (io.ReadCloser, error) {
diff --git a/tools/nixery/storage/storage.go b/tools/nixery/storage/storage.go
index 4040ef08dc9c..fd496f440ae3 100644
--- a/tools/nixery/storage/storage.go
+++ b/tools/nixery/storage/storage.go
@@ -36,7 +36,7 @@ type Backend interface {
 	// It needs to return the SHA256 hash of the data written as
 	// well as the total number of bytes, as those are required
 	// for the image manifest.
-	Persist(context.Context, string, Persister) (string, int64, error)
+	Persist(ctx context.Context, path, contentType string, f Persister) (string, int64, error)
 
 	// Fetch retrieves data from the storage backend.
 	Fetch(ctx context.Context, path string) (io.ReadCloser, error)