Add code for resumable downloads from S3

endpoints/registry.py

@@ -101,6 +101,13 @@ def get_image_layer(namespace, repository, image_id, headers):
     profile.debug('Looking up repo image')
     repo_image = model.get_repo_image(namespace, repository, image_id)
 
+    # Add the Accept-Ranges header if the storage engine supports resumable
+    # downloads.
+    extra_headers = {}
+
+    if store.get_supports_resumable_downloads():
+      extra_headers['Accept-Ranges'] = 'bytes';
+
     profile.debug('Looking up the layer path')
     try:
       path = store.image_layer_path(repo_image.storage.uuid)
@@ -110,10 +117,12 @@ def get_image_layer(namespace, repository, image_id, headers):
 
       if direct_download_url:
         profile.debug('Returning direct download URL')
-        return redirect(direct_download_url)
+        resp = redirect(direct_download_url)
+        resp.headers = dict(headers, **extra_headers)
+        return resp
 
       profile.debug('Streaming layer data')
-      return Response(store.stream_read(repo_image.storage.locations, path), headers=headers)
+      return Response(store.stream_read(repo_image.storage.locations, path), headers=dict(headers, **extra_headers))
     except (IOError, AttributeError):
       profile.debug('Image not found')
       abort(404, 'Image %(image_id)s not found', issue='unknown-image',

storage/basestorage.py

@@ -57,6 +57,9 @@ class BaseStorage(StoragePaths):
   def get_direct_download_url(self, path, expires_in=60):
     return None
 
+  def get_supports_resumable_downloads(self):
+    return False
+
   def get_content(self, path):
     raise NotImplementedError
 

storage/s3.py

@@ -83,6 +83,9 @@ class S3Storage(BaseStorage):
     key.set_contents_from_string(content, encrypt_key=True)
     return path
 
+  def get_supports_resumable_downloads(self):
+    return True
+
   def get_direct_download_url(self, path, expires_in=60):
     self._initialize_s3()
     path = self._init_path(path)