Refactor revoke_model to remove circular dependency

In the process of caching service providers, a circular dependency was
uncovered between keystone's caching module and the revoke_model. This change
isolates the refactor to fix the circular dependency into it's own patch. A
separate follow on patch will add caching to service providers on token
creation and validation.

Change-Id: Iaa3c30d51270089b2d5999383d60ed0b2f7f56c8

keystone/common/cache/_context_cache.py

@@ -17,33 +17,15 @@ from oslo_context import context as oslo_context
 from oslo_serialization import msgpackutils
 
 
-from keystone.models import revoke_model
-
-
-class _RevokeEventHandler(object):
-    # NOTE(morganfainberg): There needs to be reserved "registry" entries set
-    # in oslo_serialization for application-specific handlers. We picked 127
-    # here since it's waaaaaay far out before oslo_serialization will use it.
-    identity = 127
-    handles = (revoke_model.RevokeEvent,)
-
-    def __init__(self, registry):
-        self._registry = registry
-
-    def serialize(self, obj):
-        return msgpackutils.dumps(obj.__dict__, registry=self._registry)
-
-    def deserialize(self, data):
-        revoke_event_data = msgpackutils.loads(data, registry=self._registry)
-        revoke_event = revoke_model.RevokeEvent(**revoke_event_data)
-        return revoke_event
-
-
 # Register our new handler.
 _registry = msgpackutils.default_registry
-_registry.frozen = False
-_registry.register(_RevokeEventHandler(registry=_registry))
-_registry.frozen = True
+
+
+def _register_model_handler(handler_class):
+    """Register a new model handler."""
+    _registry.frozen = False
+    _registry.register(handler_class(registry=_registry))
+    _registry.frozen = True
 
 
 class _ResponseCacheProxy(proxy.ProxyBackend):

keystone/common/cache/core.py

@@ -25,6 +25,9 @@ CONF = cfg.CONF
 CACHE_REGION = cache.create_region()
 
 
+register_model_handler = _context_cache._register_model_handler
+
+
 def configure_cache(region=None):
     if region is None:
         region = CACHE_REGION

keystone/models/revoke_model.py

@@ -10,9 +10,11 @@
 # License for the specific language governing permissions and limitations
 # under the License.
 
+from oslo_serialization import msgpackutils
 from oslo_utils import timeutils
 from six.moves import map
 
+from keystone.common import cache
 from keystone.common import utils
 
 
@@ -323,3 +325,25 @@ def build_token_values(token_data):
         token_values['consumer_id'] = oauth1['consumer_id']
         token_values['access_token_id'] = oauth1['access_token_id']
     return token_values
+
+
+class _RevokeEventHandler(object):
+    # NOTE(morganfainberg): There needs to be reserved "registry" entries set
+    # in oslo_serialization for application-specific handlers. We picked 127
+    # here since it's waaaaaay far out before oslo_serialization will use it.
+    identity = 127
+    handles = (RevokeEvent,)
+
+    def __init__(self, registry):
+        self._registry = registry
+
+    def serialize(self, obj):
+        return msgpackutils.dumps(obj.__dict__, registry=self._registry)
+
+    def deserialize(self, data):
+        revoke_event_data = msgpackutils.loads(data, registry=self._registry)
+        revoke_event = RevokeEvent(**revoke_event_data)
+        return revoke_event
+
+
+cache.register_model_handler(_RevokeEventHandler)