Only call get_engine().pool.dispose if _FACADE

Avoid calling neutron.db.api.get_engine().pool.dispose() if
an engine facade has not yet been created since there won't
be any connections to get rid of. Calling it on services
that do not use the DB (e.g. agents) unnecessarily creates
a database connection engine that will never be used.

Change-Id: I3dbad1bef5da7b3765898e7d539b4d119b89e73a
Closes-Bug: #1433536

neutron/agent/metadata_agent.py

@@ -37,7 +37,5 @@ def main():
     config.init(sys.argv[1:])
     config.setup_logging()
     utils.log_opt_values(LOG)
-    # metadata agent need not connect DB
-    cfg.CONF.set_override("connection", "", "database")
     proxy = agent.UnixDomainMetadataProxy(cfg.CONF)
     proxy.run()

neutron/db/api.py

@@ -40,6 +40,12 @@ def get_engine():
     return facade.get_engine()
 
 
+def dispose():
+    # Don't need to do anything if an enginefacade hasn't been created
+    if _FACADE is not None:
+        get_engine().pool.dispose()
+
+
 def get_session(autocommit=True, expire_on_commit=False):
     """Helper method to grab session."""
     facade = _create_facade_lazily()

neutron/service.py

@@ -119,7 +119,7 @@ class RpcWorker(object):
         # We may have just forked from parent process.  A quick disposal of the
         # existing sql connections avoids producing errors later when they are
         # discovered to be broken.
-        session.get_engine().pool.dispose()
+        session.dispose()
         self._servers = self._plugin.start_rpc_listeners()
 
     def wait(self):

neutron/tests/unit/agent/metadata/test_agent.py

@@ -587,8 +587,6 @@ class TestUnixDomainMetadataProxy(base.BaseTestCase):
                             mock.call(cfg.CONF),
                             mock.call().run()]
                         )
-                        cfg.CONF.set_override.assert_called_once_with(
-                            "connection", "", "database")
 
     def test_init_state_reporting(self):
         with mock.patch('os.makedirs'):

neutron/tests/unit/test_wsgi.py

@@ -25,6 +25,7 @@ import webob
 import webob.exc
 
 from neutron.common import exceptions as exception
+from neutron.db import api
 from neutron.tests import base
 from neutron import wsgi
 
@@ -52,18 +53,17 @@ def open_no_proxy(*args, **kwargs):
 class TestWorkerService(base.BaseTestCase):
     """WorkerService tests."""
 
-    @mock.patch('neutron.db.api')
+    @mock.patch('neutron.db.api.get_engine')
     def test_start_withoutdb_call(self, apimock):
+        # clear engine from other tests
+        api._FACADE = None
         _service = mock.Mock()
-        _service.pool = mock.Mock()
-        _service.pool.spawn = mock.Mock()
         _service.pool.spawn.return_value = None
 
         _app = mock.Mock()
-        cfg.CONF.set_override("connection", "", "database")
         workerservice = wsgi.WorkerService(_service, _app)
         workerservice.start()
-        self.assertFalse(apimock.get_engine.called)
+        self.assertFalse(apimock.called)
 
 
 class TestWSGIServer(base.BaseTestCase):

neutron/wsgi.py

@@ -101,8 +101,7 @@ class WorkerService(object):
         # We may have just forked from parent process.  A quick disposal of the
         # existing sql connections avoids producing 500 errors later when they
         # are discovered to be broken.
-        if CONF.database.connection:
+        api.dispose()
-            api.get_engine().pool.dispose()
         self._server = self._service.pool.spawn(self._service._run,
                                                 self._application,
                                                 self._service._socket)