Add WaitEvent to the API

The ability to wait on an event to complete is a useful construct.
Instead of just having a one-off class to do it in the functional
tests, add it to the formal API.

There were some pylint issues with unused variables that are also
fixed in this patch.

Change-Id: Ie6d7c2ab384e152776b3d5f000c4ee405a8a3974

ovsdbapp/backend/ovs_idl/event.py

@@ -39,3 +39,7 @@ class RowEvent(ovsdb_event.RowEvent):  # pylint: disable=abstract-method
         LOG.debug("%s : Matched %s, %s, %s %s", self.event_name, self.table,
                   self.events, self.conditions, self.old_conditions)
         return True
+
+
+class WaitEvent(RowEvent, ovsdb_event.WaitEvent):
+    pass

ovsdbapp/event.py

@@ -68,6 +68,26 @@ class RowEvent(object):
         """Method to run when the event matches"""
 
 
+class WaitEvent(RowEvent):
+    event_name = 'WaitEvent'
+    ONETIME = True
+
+    def __init__(self, *args, **kwargs):
+        self.event = threading.Event()
+        self.timeout = kwargs.pop('timeout', None)
+        super(WaitEvent, self).__init__(*args, **kwargs)
+
+    @abc.abstractmethod
+    def matches(self, event, row, old=None):
+        """Test that `event on `row` matches watched events. See: RowEvent"""
+
+    def run(self, event, row, old):
+        self.event.set()
+
+    def wait(self):
+        return self.event.wait(self.timeout)
+
+
 class RowEventHandler(object):
     def __init__(self):
         self.__watched_events = set()

ovsdbapp/tests/functional/schema/ovn_southbound/test_impl_idl.py

@@ -10,8 +10,6 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
-import threading
-
 from ovsdbapp.backend.ovs_idl import event
 from ovsdbapp.backend.ovs_idl import idlutils
 from ovsdbapp import event as ovsdb_event
@@ -22,21 +20,13 @@ from ovsdbapp.tests.functional.schema.ovn_southbound import fixtures
 from ovsdbapp.tests import utils
 
 
-class WaitForPortBindingEvent(event.RowEvent):
+class WaitForPortBindingEvent(event.WaitEvent):
     event_name = 'WaitForPortBindingEvent'
-    ONETIME = True
 
     def __init__(self, port, timeout=5):
-        self.event = threading.Event()
-        self.timeout = timeout
         super(WaitForPortBindingEvent, self).__init__(
-            (self.ROW_CREATE,), 'Port_Binding', (('logical_port', '=', port),))
-
-    def run(self, event, row, old):
-        self.event.set()
-
-    def wait(self):
-        self.event.wait(self.timeout)
+            (self.ROW_CREATE,), 'Port_Binding', (('logical_port', '=', port),),
+            timeout=timeout)
 
 
 class OvnSouthboundTest(base.FunctionalTestCase):
@@ -109,7 +99,7 @@ class OvnSouthboundTest(base.FunctionalTestCase):
         with self.nbapi.transaction(check_error=True) as txn:
             switch = txn.add(self.nbapi.ls_add(sname))
             port = txn.add(self.nbapi.lsp_add(sname, pname))
-        row_event.wait()
+        self.assertTrue(row_event.wait())
         return chassis, switch.result, port.result
 
     def test_lsp_bind(self):
@@ -121,12 +111,12 @@ class OvnSouthboundTest(base.FunctionalTestCase):
         return chassis, switch, port
 
     def test_lsp_bind_exists(self):
-        chassis, switch, port = self.test_lsp_bind()
+        chassis, _switch, port = self.test_lsp_bind()
         cmd = self.api.lsp_bind(port.name, chassis.name)
         self.assertRaises(RuntimeError, cmd.execute, check_error=True)
 
     def test_lsp_bind_may_exist(self):
-        chassis, switch, port = self.test_lsp_bind()
+        chassis, _switch, port = self.test_lsp_bind()
         other = self._chassis_add(['vxlan'], '192.0.2.2',
                                   chassis=utils.get_rand_device_name())
         self.api.lsp_bind(port.name, other.name, may_exist=True).execute(
@@ -137,7 +127,7 @@ class OvnSouthboundTest(base.FunctionalTestCase):
         self.assertIn(chassis, binding.chassis)
 
     def test_lsp_unbind(self):
-        chassis, switch, port = self.test_lsp_bind()
+        _chassis, _switch, port = self.test_lsp_bind()
         self.api.lsp_unbind(port.name).execute(check_error=True)
         binding = idlutils.row_by_value(self.api.idl, 'Port_Binding',
                                         'logical_port', port.name)