Properly handle the empty layer when pushing schema 2 manifests

Docker doesn't send us the contents of this layer, so we are forced to synthesize it ourselves

test/registry/protocol_fixtures.py

@@ -24,7 +24,6 @@ def basic_images():
   ]
 
 
-
 @pytest.fixture(scope="session")
 def different_images():
   """ Returns different basic images for push and pull testing. """
@@ -37,7 +36,6 @@ def different_images():
   ]
 
 
-
 @pytest.fixture(scope="session")
 def sized_images():
   """ Returns basic images (with sizes) for push and pull testing. """
@@ -106,6 +104,24 @@ def remote_images():
   ]
 
 
+@pytest.fixture(scope="session")
+def images_with_empty_layer():
+  """ Returns images for push and pull testing that contain an empty layer. """
+  # Note: order is from base layer down to leaf.
+  parent_bytes = layer_bytes_for_contents('parent contents')
+  empty_bytes = layer_bytes_for_contents('', empty=True)
+  image_bytes = layer_bytes_for_contents('some contents')
+  middle_bytes = layer_bytes_for_contents('middle')
+
+  return [
+    Image(id='parentid', bytes=parent_bytes, parent_id=None),
+    Image(id='emptyid', bytes=empty_bytes, parent_id='parentid', is_empty=True),
+    Image(id='middleid', bytes=middle_bytes, parent_id='emptyid'),
+    Image(id='emptyid2', bytes=empty_bytes, parent_id='middleid', is_empty=True),
+    Image(id='someid', bytes=image_bytes, parent_id='emptyid2'),
+  ]
+
+
 @pytest.fixture(scope="session")
 def jwk():
   return RSAKey(key=RSA.generate(2048))
@@ -161,10 +177,10 @@ def legacy_pusher(request, data_model, jwk):
 
 @pytest.fixture(params=['v1', 'v2_1', 'v2_2'])
 def puller(request, data_model, jwk):
-  if request == 'v1':
+  if request.param == 'v1':
     return V1Protocol(jwk)
 
-  if request == 'v2_2' and data_model == 'oci_model':
+  if request.param == 'v2_2' and data_model == 'oci_model':
     return V2Protocol(jwk, schema2=True)
 
   return V2Protocol(jwk)

test/registry/protocol_v2.py

@@ -249,7 +249,21 @@ class V2Protocol(RegistryProtocol):
       if options.manifest_invalid_blob_references:
         checksum = 'sha256:' + hashlib.sha256('notarealthing').hexdigest()
 
-      builder.add_layer(checksum, len(image.bytes), urls=image.urls)
+      if not image.is_empty:
+        builder.add_layer(checksum, len(image.bytes), urls=image.urls)
+
+    def history_for_image(image):
+      history = {
+        'created': '2018-04-03T18:37:09.284840891Z',
+        'created_by': (('/bin/sh -c #(nop) ENTRYPOINT %s' % image.config['Entrypoint'])
+                       if image.config and image.config.get('Entrypoint')
+                       else '/bin/sh -c #(nop) %s' % image.id),
+      }
+
+      if image.is_empty:
+        history['empty_layer'] = True
+
+      return history
 
     config = {
       "os": "linux",
@@ -257,12 +271,7 @@ class V2Protocol(RegistryProtocol):
         "type": "layers",
         "diff_ids": []
       },
-      "history": [{
-        'created': '2018-04-03T18:37:09.284840891Z',
-        'created_by': (('/bin/sh -c #(nop) ENTRYPOINT %s' % image.config['Entrypoint'])
-                       if image.config and image.config.get('Entrypoint')
-                       else '/bin/sh -c #(nop) %s' % image.id),
-      } for image in images],
+      "history": [history_for_image(image) for image in images],
     }
 
     if images[-1].config:
@@ -535,17 +544,28 @@ class V2Protocol(RegistryProtocol):
         image_ids[tag_name] = manifest.leaf_layer_v1_image_id
 
       # Verify the layers.
-      for index, layer in enumerate(manifest.layers):
+      layer_index = 0
+      empty_count = 0
+      for image in images:
+        if manifest.schema_version == 2 and image.is_empty:
+          empty_count += 1
+          continue
+
         # If the layer is remote, then we expect the blob to *not* exist in the system.
-        expected_status = 404 if images[index].urls else 200
+        layer = manifest.layers[layer_index]
+        expected_status = 404 if image.urls else 200
         result = self.conduct(session, 'GET',
                               '/v2/%s/blobs/%s' % (self.repo_name(namespace, repo_name),
                                                    layer.digest),
                               expected_status=expected_status,
                               headers=headers)
-        
+
         if expected_status == 200:
-          assert result.content == images[index].bytes
+          assert result.content == image.bytes
+
+        layer_index += 1
+
+      assert (len(manifest.layers) + empty_count) == len(images)
 
     return PullResult(manifests=manifests, image_ids=image_ids)
 

test/registry/protocols.py

@@ -7,14 +7,20 @@ from cStringIO import StringIO
 from enum import Enum, unique
 from six import add_metaclass
 
-Image = namedtuple('Image', ['id', 'parent_id', 'bytes', 'size', 'config', 'created', 'urls'])
-Image.__new__.__defaults__ = (None, None, None, None)
+from image.docker.schema2 import EMPTY_LAYER_BYTES
+
+Image = namedtuple('Image', ['id', 'parent_id', 'bytes', 'size', 'config', 'created', 'urls',
+                             'is_empty'])
+Image.__new__.__defaults__ = (None, None, None, None, False)
 
 PushResult = namedtuple('PushResult', ['manifests', 'headers'])
 PullResult = namedtuple('PullResult', ['manifests', 'image_ids'])
 
 
-def layer_bytes_for_contents(contents, mode='|gz', other_files=None):
+def layer_bytes_for_contents(contents, mode='|gz', other_files=None, empty=False):
+  if empty:
+    return EMPTY_LAYER_BYTES
+
   layer_data = StringIO()
   tar_file = tarfile.open(fileobj=layer_data, mode='w' + mode)
 

test/registry/registry_tests.py

@@ -39,6 +39,19 @@ def test_basic_push_pull(pusher, puller, basic_images, liveserver_session, app_r
               credentials=credentials)
 
 
+def test_empty_layer(pusher, puller, images_with_empty_layer, liveserver_session, app_reloader):
+  """ Test: Push and pull of an image with an empty layer to a new repository. """
+  credentials = ('devtable', 'password')
+
+  # Push a new repository.
+  pusher.push(liveserver_session, 'devtable', 'newrepo', 'latest', images_with_empty_layer,
+              credentials=credentials)
+
+  # Pull the repository to verify.
+  puller.pull(liveserver_session, 'devtable', 'newrepo', 'latest', images_with_empty_layer,
+              credentials=credentials)
+
+
 def test_multi_layer_images_push_pull(pusher, puller, multi_layer_images, liveserver_session,
                                       app_reloader):
   """ Test: Basic push and pull of a multi-layered image to a new repository. """