Make DBAPI class work with mocks correctly

Currently, DBAPI __getattr__() implementation will *always*
implicitly wrap all mocked methods of a target class/module using
wrap_db_retry(), as retry_on_* attributes will always exist and be
true for mock instances. Not only this leads to a situation, when
we would retry methods, we were not going to retry, but this also
fails with AttributeError on functools.wraps() call, breaking valid
unit tests in projects.

DBAPI is changed in a way, so that it does dict look ups instead of
fetching instance attributes to ensure mocked methods are handled
correctly and aren't wrapped when they shouldn't be wrapped.

Related issue:
http://stackoverflow.com/questions/22204660/python-mock-wrapsf-problems

Change-Id: I36550ffa88056c53a431d64e61e84fbb44bbf68d

oslo_db/api.py

@@ -56,7 +56,7 @@ def safe_for_db_retry(f):
     :param f: database api method.
     :type f: function.
     """
-    f.enable_retry_on_disconnect = True
+    f.__dict__['enable_retry_on_disconnect'] = True
     return f
 
 
@@ -66,7 +66,7 @@ def retry_on_deadlock(f):
     wrap_db_entry will be applied to all db.api functions marked with this
     decorator.
     """
-    f.enable_retry_on_deadlock = True
+    f.__dict__['enable_retry_on_deadlock'] = True
     return f
 
 
@@ -76,7 +76,7 @@ def retry_on_request(f):
     wrap_db_entry will be applied to all db.api functions marked with this
     decorator.
     """
-    f.enable_retry_on_request = True
+    f.__dict__['enable_retry_on_request'] = True
     return f
 
 
@@ -225,10 +225,11 @@ class DBAPI(object):
         # NOTE(vsergeyev): If `use_db_reconnect` option is set to True, retry
         #                  DB API methods, decorated with @safe_for_db_retry
         #                  on disconnect.
-        retry_on_disconnect = self.use_db_reconnect and getattr(
-            attr, 'enable_retry_on_disconnect', False)
-        retry_on_deadlock = getattr(attr, 'enable_retry_on_deadlock', False)
-        retry_on_request = getattr(attr, 'enable_retry_on_request', False)
+        retry_on_disconnect = self.use_db_reconnect and attr.__dict__.get(
+            'enable_retry_on_disconnect', False)
+        retry_on_deadlock = attr.__dict__.get('enable_retry_on_deadlock',
+                                              False)
+        retry_on_request = attr.__dict__.get('enable_retry_on_request', False)
 
         if retry_on_disconnect or retry_on_deadlock or retry_on_request:
             attr = wrap_db_retry(

oslo_db/tests/test_api.py

@@ -196,3 +196,11 @@ class DBRetryRequestCase(DBAPITestCase):
         res = {'result': 0}
         self.assertRaises(ValueError, some_method, res)
         self.assertEqual(max_retries + 1, res['result'])
+
+    @mock.patch.object(DBAPI, 'api_class_call1')
+    @mock.patch.object(api, 'wrap_db_retry')
+    def test_mocked_methods_are_not_wrapped(self, mocked_wrap, mocked_method):
+        dbapi = api.DBAPI('oslo_db.tests.test_api')
+        dbapi.api_class_call1()
+
+        self.assertFalse(mocked_wrap.called)