Fix _poll_connection not timeout issue (2/2)

Backport bugfix about the last cherry-pick.

The title of the commit in master was:
  rabbit: fix timeout timer when duration is None

but this was changed since it didn't describe the actual change.

Change-Id: I7f4cb3075f776c63aa7dc497173677f92b68c16d
(cherry picked from commit 44132d4344902f98007e6e58ea3bee56c701b400)

2 files changed, 17 insertions, 2 deletions

diff --git a/oslo/messaging/_drivers/common.py b/oslo/messaging/_drivers/common.py
index 24fee5e..a8137bd 100644
--- a/oslo/messaging/_drivers/common.py
+++ b/oslo/messaging/_drivers/common.py
@@ -360,13 +360,13 @@ class DecayingTimer(object):
             self._ends_at = time.time() + max(0, self._duration)
 
     def check_return(self, timeout_callback, *args, **kwargs):
+        maximum = kwargs.pop('maximum', None)
         if self._duration is None:
-            return None
+            return None if maximum is None else maximum
         if self._ends_at is None:
             raise RuntimeError(_("Can not check/return a timeout from a timer"
                                " that has not been started."))
 
-        maximum = kwargs.pop('maximum', None)
         left = self._ends_at - time.time()
         if left <= 0:
             timeout_callback(*args, **kwargs)
diff --git a/tests/test_utils.py b/tests/test_utils.py
index 1321009..38ee1d0 100644
--- a/tests/test_utils.py
+++ b/tests/test_utils.py
@@ -13,6 +13,7 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
+from oslo.messaging._drivers import common
 from oslo.messaging import _utils as utils
 from tests import utils as test_utils
 
@@ -47,3 +48,17 @@ class VersionIsCompatibleTestCase(test_utils.BaseTestCase):
 
     def test_version_is_compatible_no_rev_is_zero(self):
         self.assertTrue(utils.version_is_compatible('1.23.0', '1.23'))
+
+
+class TimerTestCase(test_utils.BaseTestCase):
+    def test_duration_is_none(self):
+        t = common.DecayingTimer()
+        t.start()
+        remaining = t.check_return(None)
+        self.assertEqual(None, remaining)
+
+    def test_duration_is_none_and_maximun_set(self):
+        t = common.DecayingTimer()
+        t.start()
+        remaining = t.check_return(None, maximum=2)
+        self.assertEqual(2, remaining)