Cache default security group IDs in memory

Getting default SG for a project is quite a frequent operation
that happens for example on each port create/update events.
Since default SG id does not change often for a project/tenant
(if at all) it makes sense to cache it in memory to avoid DB access
each time.

Change-Id: I2493eb65ddd548435cf846e1ae7ac65ce8bc14a4

neutron/db/securitygroups_db.py

@@ -59,6 +59,8 @@ class SecurityGroupDbMixin(ext_sg.SecurityGroupPluginBase,
 
     __native_bulk_support = True
 
+    default_sg_cache = dict()
+
     def create_security_group_bulk(self, context, security_groups):
         return self._create_bulk('security_group', context,
                                  security_groups)
@@ -275,6 +277,9 @@ class SecurityGroupDbMixin(ext_sg.SecurityGroupPluginBase,
                                   **kwargs)
             sg.delete()
 
+        project_id = self.default_sg_cache.pop(id, None)
+        self.default_sg_cache.pop(project_id, None)
+
         kwargs.pop('security_group')
         kwargs['name'] = sg['name']
         registry.notify(resources.SECURITY_GROUP, events.AFTER_DELETE,
@@ -881,11 +886,16 @@ class SecurityGroupDbMixin(ext_sg.SecurityGroupPluginBase,
                                        security_groups else [])
 
     def _get_default_sg_id(self, context, tenant_id):
+        if tenant_id in self.default_sg_cache:
+            return self.default_sg_cache[tenant_id]
+
         default_group = sg_obj.DefaultSecurityGroup.get_object(
             context,
             project_id=tenant_id,
         )
         if default_group:
+            self.default_sg_cache[tenant_id] = default_group.security_group_id
+            self.default_sg_cache[default_group.security_group_id] = tenant_id
             return default_group.security_group_id
 
     @registry.receives(resources.PORT, [events.BEFORE_CREATE,

neutron/tests/base.py

@@ -55,6 +55,7 @@ from neutron.api.rpc.callbacks.producer import registry as rpc_producer_reg
 from neutron.common import config
 from neutron.conf.agent import common as agent_config
 from neutron.db import agentschedulers_db
+from neutron.db import securitygroups_db
 from neutron import manager
 from neutron import policy
 from neutron.quota import resource_registry
@@ -570,6 +571,8 @@ class PluginFixture(fixtures.Fixture):
         # TODO(marun) Fix plugins that do not properly initialize notifiers
         agentschedulers_db.AgentSchedulerDbMixin.agent_notifiers = {}
 
+        securitygroups_db.SecurityGroupDbMixin.default_sg_cache = {}
+
         nm.clear_instance()