Remove polling from test_create_bridges

It is possible to use ovsdbapp Events to wait for bridges to be
created instead of polling until they exist.

Change-Id: I97f1c15a13a3bb90d774066a9933f3a4d39f50e2

neutron/tests/functional/agent/ovsdb/native/test_connection.py

@@ -13,11 +13,38 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
+import threading
+
+from ovsdbapp import event
+
 from neutron.agent.common import ovs_lib
-from neutron.common import utils as common_utils
 from neutron.tests.functional import base
 
 
+class WaitForBridgesEvent(event.RowEvent):
+    event_name = 'WaitForBridgesEvent'
+    ONETIME = True
+
+    def __init__(self, bridges, timeout=5):
+        self.bridges_not_seen = set(bridges)
+        self.timeout = timeout
+        self.event = threading.Event()
+        super(WaitForBridgesEvent, self).__init__(
+            (self.ROW_CREATE,), 'Bridge', None)
+
+    def matches(self, event, row, old=None):
+        if event not in self.events or row._table.name != self.table:
+            return False
+        self.bridges_not_seen.discard(row.name)
+        return not self.bridges_not_seen
+
+    def run(self, event, row, old):
+        self.event.set()
+
+    def wait(self):
+        return self.event.wait(self.timeout)
+
+
 class BridgeMonitorTestCase(base.BaseLoggingTestCase):
 
     def _delete_bridges(self, bridges):
@@ -25,23 +52,16 @@ class BridgeMonitorTestCase(base.BaseLoggingTestCase):
             self.ovs.delete_bridge(bridge)
 
     def test_create_bridges(self):
-        bridges_added = []
         bridges_to_monitor = ['br01', 'br02', 'br03']
         bridges_to_create = ['br01', 'br02', 'br03', 'br04', 'br05']
         self.ovs = ovs_lib.BaseOVS()
         self.ovs.ovsdb.idl_monitor.start_bridge_monitor(bridges_to_monitor)
         self.addCleanup(self._delete_bridges, bridges_to_create)
-
+        event = WaitForBridgesEvent(bridges_to_monitor)
+        self.ovs.ovsdb.idl_monitor.notify_handler.watch_event(event)
         for bridge in bridges_to_create:
             self.ovs.add_bridge(bridge)
-
-        def retrieve_bridges(bridges_added):
-            bridges_added += self.ovs.ovsdb.idl_monitor.bridges_added
-            return len(bridges_added)
-
-        common_utils.wait_until_true(
-            lambda: retrieve_bridges(bridges_added) == len(bridges_to_monitor),
-            timeout=5)
-        bridges_added.sort()
-        self.assertEqual(bridges_to_monitor, bridges_added)
+        self.assertTrue(event.wait())
+        self.assertEqual(bridges_to_monitor,
+                         self.ovs.ovsdb.idl_monitor.bridges_added)
         self.assertEqual([], self.ovs.ovsdb.idl_monitor.bridges_added)