Add before_put_image_json signal

Add before_put_image_json signal that allows receivers to short-circuit
the put if they return any non-None value. This can be useful for things
such as enforcing quotas, e.g. by having a custom extension connect to
this signal, check the layer's Size, and returning something to the
effect that the put was denied due to quota.

Signed-off-by: Andy Goldstein <agoldste@redhat.com>

Author: Andy Goldstein

docker_registry/images.py

@@ -19,6 +19,7 @@
 from .lib import checksums
 from .lib import layers
 from .lib import mirroring
+from .lib import signals
 # this is our monkey patched snippet from python v2.7.6 'tarfile'
 # with xattr support
 from .lib.xtarfile import tarfile
@@ -370,6 +371,13 @@ def put_image_json(image_id):
     mark_path = store.image_mark_path(image_id)
     if store.exists(json_path) and not store.exists(mark_path):
         return toolkit.api_error('Image already exists', 409)
+
+    sender = flask.current_app._get_current_object()
+    signal_result = signals.before_put_image_json.send(sender, image_json=data)
+    for result_pair in signal_result:
+        if result_pair[1] is not None:
+            return toolkit.api_error(result_pair[1])
+
     # If we reach that point, it means that this is a new image or a retry
     # on a failed push
     store.put_content(mark_path, 'true')

docker_registry/lib/signals.py

@@ -13,3 +13,8 @@
 # Triggered when a tag is modified (registry/tags.py)
 tag_created = _signals.signal('tag-created')
 tag_deleted = _signals.signal('tag-deleted')
+
+# Triggered after all put_image_json validations have passed but before
+# actually storing anything. Any non-None return value from the signalled
+# subscribers will result in the put_image_json operation being cancelled.
+before_put_image_json = _signals.signal('before-put-image-json')

tests/test_images.py

@@ -6,6 +6,7 @@
 
 from docker_registry.core import compat
 import docker_registry.images as images
+import docker_registry.lib.signals as signals
 
 json = compat.json
 
@@ -79,3 +80,37 @@ def test_bytes_range(self):
         msg = 'expected size: {0}; got: {1}'.format(len(expected_data),
                                                     len(received_data))
         self.assertEqual(expected_data, received_data, msg)
+
+    def before_put_image_json_handler_ok(self, sender, image_json):
+        return None
+
+    def before_put_image_json_handler_not_ok(self, sender, image_json):
+        return "Not ok"
+
+    def test_before_put_image_json_ok(self):
+        image_id = self.gen_random_string()
+        json_obj = {
+            'id': image_id
+        }
+        json_data = compat.json.dumps(json_obj)
+        with signals.before_put_image_json.connected_to(
+                self.before_put_image_json_handler_ok):
+            resp = self.http_client.put('/v1/images/{0}/json'.format(image_id),
+                                        data=json_data)
+            self.assertEqual(resp.status_code, 200, resp.data)
+
+    def test_before_put_image_json_not_ok(self):
+        image_id = self.gen_random_string()
+        json_obj = {
+            'id': image_id
+        }
+        json_data = compat.json.dumps(json_obj)
+        with signals.before_put_image_json.connected_to(
+                self.before_put_image_json_handler_not_ok):
+            resp = self.http_client.put('/v1/images/{0}/json'.format(image_id),
+                                        data=json_data)
+            resp_data = json.loads(resp.data)
+            self.assertEqual(resp.status_code, 400, resp.data)
+            self.assertTrue('error' in resp_data,
+                            'Expected error key in response')
+            self.assertEqual(resp_data['error'], 'Not ok', resp.data)