Merge "Add retry support to pecan"

neutron/pecan_wsgi/controllers/utils.py

@@ -13,27 +13,76 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
+import copy
+import functools
+
+from neutron_lib import constants
 import pecan
 from pecan import request
 
 from neutron.api.v2 import attributes as api_attributes
+from neutron.db import api as db_api
 from neutron import manager
 
 # Utility functions for Pecan controllers.
 
 
-def expose(*args, **kwargs):
+class Fakecode(object):
+    co_varnames = ()
+
+
+def _composed(*decorators):
+    """Takes a list of decorators and returns a single decorator."""
+
+    def final_decorator(f):
+        for d in decorators:
+            # workaround for pecan bug that always assumes decorators
+            # have a __code__ attr
+            if not hasattr(d, '__code__'):
+                setattr(d, '__code__', Fakecode())
+            f = d(f)
+        return f
+    return final_decorator
+
+
+def _protect_original_resources(f):
+    """Wrapper to ensure that mutated resources are discarded on retries."""
+
+    @functools.wraps(f)
+    def wrapped(*args, **kwargs):
+        ctx = request.context
+        if 'resources' in ctx:
+            orig = ctx.get('protected_resources')
+            if not orig:
+                # this is the first call so we just take the whole reference
+                ctx['protected_resources'] = ctx['resources']
+            # TODO(blogan): Once bug 157751 is fixed and released in
+            # neutron-lib this memo will no longer be needed.  This is just
+            # quick way to not depend on a release of neutron-lib.
+            # The version that has that bug fix will need to be updated in
+            # neutron-lib.
+            memo = {id(constants.ATTR_NOT_SPECIFIED):
+                    constants.ATTR_NOT_SPECIFIED}
+            ctx['resources'] = copy.deepcopy(ctx['protected_resources'],
+                                             memo=memo)
+        return f(*args, **kwargs)
+    return wrapped
+
+
+def _pecan_generator_wrapper(func, *args, **kwargs):
     """Helper function so we don't have to specify json for everything."""
     kwargs.setdefault('content_type', 'application/json')
     kwargs.setdefault('template', 'json')
-    return pecan.expose(*args, **kwargs)
+    return _composed(_protect_original_resources, db_api.retry_db_errors,
+                     func(*args, **kwargs))
+
+
+def expose(*args, **kwargs):
+    return _pecan_generator_wrapper(pecan.expose, *args, **kwargs)
 
 
 def when(index, *args, **kwargs):
-    """Helper function so we don't have to specify json for everything."""
-    kwargs.setdefault('content_type', 'application/json')
-    kwargs.setdefault('template', 'json')
-    return index.when(*args, **kwargs)
+    return _pecan_generator_wrapper(index.when, *args, **kwargs)
 
 
 class NeutronPecanController(object):

neutron/tests/functional/pecan_wsgi/test_controllers.py

@@ -15,6 +15,7 @@ from collections import namedtuple
 import mock
 from neutron_lib import constants as n_const
 from oslo_config import cfg
+from oslo_db import exception as db_exc
 from oslo_policy import policy as oslo_policy
 from oslo_serialization import jsonutils
 import pecan
@@ -268,6 +269,26 @@ class TestResourceController(TestRootController):
             headers={'X-Project-Id': 'tenid'})
         self.assertEqual(response.status_int, 201)
 
+    def test_post_with_retry(self):
+        self._create_failed = False
+        orig = self.plugin.create_port
+
+        def new_create(*args, **kwargs):
+            if not self._create_failed:
+                self._create_failed = True
+                raise db_exc.RetryRequest(ValueError())
+            return orig(*args, **kwargs)
+
+        with mock.patch.object(self.plugin, 'create_port',
+                               new=new_create):
+            response = self.app.post_json(
+                '/v2.0/ports.json',
+                params={'port': {'network_id': self.port['network_id'],
+                                 'admin_state_up': True,
+                                 'tenant_id': 'tenid'}},
+                headers={'X-Project-Id': 'tenid'})
+            self.assertEqual(201, response.status_int)
+
     def test_put(self):
         response = self.app.put_json('/v2.0/ports/%s.json' % self.port['id'],
                                      params={'port': {'name': 'test'}},