Fixes image-download error of v2

When trying to retrieve a Glance image using the v2 api, user will
get an error:

'utf8' codec can't decode byte 0xcc in position 1217: invalid continuation byte

This is because Glance client expects a response of type content-type:
application/octet-stream but it's getting a Content-Type:

text/html; charset=UTF-8 Transfer-Encoding: chunked

The root cause is Glance will return the image data from cache if
there is. However, in method _process_v2_request, the content type
has never been configured. See:
https://github.com/openstack/glance/blob/master/glance/api/middleware/cache.py#L162

Fixes bug 1193310

Change-Id: Icab5e28db63455358ab3919bd94c484411987e39

glance/api/middleware/cache.py

@@ -175,6 +175,18 @@ def _process_v2_request(self, request, image_id, image_iterator):
                                               image_meta['size'],
                                               image_iterator,
                                               notifier.Notifier())
+        # NOTE (flwang): Set the content-type, content-md5 and content-length
+        # explicitly to be consistent with the non-cache scenario.
+        # Besides, it's not worth the candle to invoke the "download" method
+        # of ResponseSerializer under image_data. Because method "download"
+        # will reset the app_iter. Then we have to call method
+        # "size_checked_iter" to avoid missing any notification. But after
+        # call "size_checked_iter", we will lose the content-md5 and
+        # content-length got by the method "download" because of this issue:
+        # https://github.com/Pylons/webob/issues/86
+        response.headers['Content-Type'] = 'application/octet-stream'
+        response.headers['Content-MD5'] = image.checksum
+        response.headers['Content-Length'] = str(image.size)
         return response
 
     def process_response(self, resp):

glance/tests/unit/test_cache_middleware.py

@@ -20,6 +20,7 @@
 import glance.api.middleware.cache
 from glance.common import exception
 from glance import context
+import glance.db.sqlalchemy.api as db
 import glance.registry.client.v1.api as registry
 from glance.tests import utils
 
@@ -234,6 +235,52 @@ def fake_get_image_size(image_id):
         cache_filter._verify_metadata(image_meta)
         self.assertTrue(image_meta['size'] == image_size)
 
+    def test_v2_process_request_response_headers(self):
+        def dummy_img_iterator():
+            for i in range(3):
+                yield i
+
+        def fake_image_get(self, image_id):
+            return {
+                    'id': 'test1',
+                    'name': 'fake_image',
+                    'status': 'Active',
+                    'created_at': '',
+                    'min_disk': '10G',
+                    'min_ram': '1024M',
+                    'protected': False,
+                    'locations': '',
+                    'checksum': 'c352f4e7121c6eae958bc1570324f17e',
+                    'owner': '',
+                    'disk_format': 'raw',
+                    'container_format': 'bare',
+                    'size': '123456789',
+                    'is_public': 'public',
+                    'deleted': False,
+                    'updated_at': '',
+                    'properties': {},
+            }
+
+        def fake_image_tag_get_all(context, image_id, session=None):
+            return None
+
+        image_id = 'test1'
+        request = webob.Request.blank('/v2/images/test1/file')
+        request.context = context.RequestContext()
+
+        self.stubs.Set(db, 'image_get', fake_image_get)
+        self.stubs.Set(db, 'image_tag_get_all', fake_image_tag_get_all)
+
+        cache_filter = ProcessRequestTestCacheFilter()
+        response = cache_filter._process_v2_request(
+            request, image_id, dummy_img_iterator)
+        self.assertEqual(response.headers['Content-Type'],
+                         'application/octet-stream')
+        self.assertEqual(response.headers['Content-MD5'],
+                         'c352f4e7121c6eae958bc1570324f17e')
+        self.assertEqual(response.headers['Content-Length'],
+                         '123456789')
+
 
 class TestProcessResponse(utils.BaseTestCase):
     def setUp(self):