Merge "Handle when a group used to exist but no longer does"

2 files changed, 42 insertions, 2 deletions

diff --git a/tooz/drivers/redis.py b/tooz/drivers/redis.py
index 8b311ab..54da9d0 100644
--- a/tooz/drivers/redis.py
+++ b/tooz/drivers/redis.py
@@ -562,6 +562,10 @@ class RedisDriver(coordination.CoordinationDriver):
                                               encoded_group,
                                               value_from_callable=True))
 
+    def _destroy_group(self, group_id):
+        """Should only be used in tests..."""
+        self._client.delete(self._encode_group_id(group_id))
+
     def get_groups(self):
 
         def _get_groups():
@@ -601,8 +605,12 @@ class RedisDriver(coordination.CoordinationDriver):
     def run_watchers(self, timeout=None):
         result = []
         for group_id in self.get_groups().get(timeout=timeout):
-            group_members = set(self.get_members(group_id)
-                                .get(timeout=timeout))
+            try:
+                group_members = self.get_members(group_id).get(timeout=timeout)
+            except coordination.GroupNotCreated:
+                group_members = set()
+            else:
+                group_members = set(group_members)
             old_group_members = self._group_members.get(group_id, set())
             for member_id in (group_members - old_group_members):
                 result.extend(
diff --git a/tooz/tests/test_coordination.py b/tooz/tests/test_coordination.py
index 509f07d..69aa39b 100644
--- a/tooz/tests/test_coordination.py
+++ b/tooz/tests/test_coordination.py
@@ -330,6 +330,38 @@ class TestAPI(testscenarios.TestWithScenarios,
         self._coord.run_watchers()
         self.assertIsNone(self.event)
 
+    def test_watch_join_group_disappear(self):
+        if not hasattr(self._coord, '_destroy_group'):
+            self.skipTest("This test only works with coordinators"
+                          " that have the ability to destroy groups.")
+
+        self._coord.create_group(self.group_id).get()
+        self._coord.watch_join_group(self.group_id, self._set_event)
+        self._coord.watch_leave_group(self.group_id, self._set_event)
+
+        member_id_test2 = self._get_random_uuid()
+        client2 = tooz.coordination.get_coordinator(self.url,
+                                                    member_id_test2)
+        client2.start()
+        client2.join_group(self.group_id).get()
+
+        while True:
+            if self._coord.run_watchers():
+                break
+        self.assertIsInstance(self.event,
+                              tooz.coordination.MemberJoinedGroup)
+        self.event = None
+
+        # Force the group to disappear...
+        self._coord._destroy_group(self.group_id)
+
+        while True:
+            if self._coord.run_watchers():
+                break
+
+        self.assertIsInstance(self.event,
+                              tooz.coordination.MemberLeftGroup)
+
     def test_watch_join_group_non_existent(self):
         self.assertRaises(tooz.coordination.GroupNotCreated,
                           self._coord.watch_join_group,