Return 204 when image data does not exist

Currently a GET on image-data in glance v2 returns 404 when data does not
exist. But according to the API docs the HTTP status code returned in this
case should be 204.

This fix makes Glance return the right HTTP status code.

Change-Id: I34cf68e96f631f05cff349329245f74aee42397c
Closes-Bug: #1251055

glance/api/middleware/cache.py

@@ -210,7 +210,8 @@ class CacheFilter(wsgi.Middleware):
         images Resource, removing image file from the cache
         if necessary
         """
-        if not 200 <= self.get_status_code(resp) < 300:
+        status_code = self.get_status_code(resp)
+        if not 200 <= status_code < 300:
             return resp
 
         try:
@@ -218,6 +219,12 @@ class CacheFilter(wsgi.Middleware):
         except TypeError:
             return resp
 
+        if method == 'GET' and status_code == 204:
+            # Bugfix:1251055 - Don't cache non-existent image files.
+            # NOTE: Both GET for an image without locations and DELETE return
+            # 204 but DELETE should be processed.
+            return resp
+
         method_str = '_process_%s_response' % method
         try:
             process_response_method = getattr(self, method_str)

glance/api/v2/image_data.py

@@ -126,8 +126,9 @@ class ImageDataController(object):
         try:
             image = image_repo.get(image_id)
             if not image.locations:
-                reason = _("No image data could be found")
-                raise exception.NotFound(reason)
+                raise exception.ImageDataNotFound()
+        except exception.ImageDataNotFound as e:
+            raise webob.exc.HTTPNoContent(explanation=unicode(e))
         except exception.NotFound as e:
             raise webob.exc.HTTPNotFound(explanation=unicode(e))
         except exception.Forbidden as e:

glance/common/exception.py

@@ -319,3 +319,7 @@ class InvalidTaskStatusTransition(TaskException, Invalid):
 
 class DuplicateLocation(Duplicate):
     message = _("The location %(location)s already exists")
+
+
+class ImageDataNotFound(NotFound):
+    message = _("No image data could be found")

glance/tests/functional/v2/test_images.py

@@ -303,7 +303,7 @@ class TestImages(functional.FunctionalTest):
         path = self._url('/v2/images/%s/file' % image_id)
         headers = self._headers()
         response = requests.get(path, headers=headers)
-        self.assertEqual(404, response.status_code)
+        self.assertEqual(204, response.status_code)
 
         # Upload some image data
         path = self._url('/v2/images/%s/file' % image_id)

glance/tests/unit/v2/test_image_data_resource.py

@@ -109,7 +109,7 @@ class TestImagesController(base.StoreClearingUnitTest):
     def test_download_no_location(self):
         request = unit_test_utils.get_fake_request()
         self.image_repo.result = FakeImage('abcd')
-        self.assertRaises(webob.exc.HTTPNotFound, self.controller.download,
+        self.assertRaises(webob.exc.HTTPNoContent, self.controller.download,
                           request, unit_test_utils.UUID2)
 
     def test_download_non_existent_image(self):