Use the oslo_utils stop watch in decaying timer

The decaying timer can now just use the functionality
of the oslo_utils stop watch to avoid having to maintain
similar information itself; now it just becomes a thin
layer ontop of that object that provides its functionality.

Change-Id: I1b014b821a6b980590ca5b4d850a515d55c42208

oslo_messaging/_drivers/common.py

@@ -18,10 +18,10 @@
 import copy
 import logging
 import sys
-import time
 import traceback
 
 from oslo_serialization import jsonutils
+from oslo_utils import timeutils
 import six
 
 import oslo_messaging
@@ -334,24 +334,16 @@ def deserialize_msg(msg):
 
 class DecayingTimer(object):
     def __init__(self, duration=None):
-        self._duration = duration
-        self._ends_at = None
+        self._watch = timeutils.StopWatch(duration=duration)
 
     def start(self):
-        if self._duration is not None:
-            self._ends_at = time.time() + max(0, self._duration)
+        self._watch.start()
 
     def check_return(self, timeout_callback=None, *args, **kwargs):
         maximum = kwargs.pop('maximum', None)
-
-        if self._duration is None:
+        left = self._watch.leftover(return_none=True)
+        if left is None:
             return maximum
-        if self._ends_at is None:
-            raise RuntimeError(_("Can not check/return a timeout from a timer"
-                               " that has not been started."))
-
-        left = self._ends_at - time.time()
         if left <= 0 and timeout_callback is not None:
             timeout_callback(*args, **kwargs)
-
         return left if maximum is None else min(left, maximum)

oslo_messaging/tests/test_utils.py

@@ -13,8 +13,6 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
-import time
-
 import mock
 
 from oslo_messaging._drivers import common
@@ -67,16 +65,24 @@ class TimerTestCase(test_utils.BaseTestCase):
         remaining = t.check_return(maximum=2)
         self.assertEqual(2, remaining)
 
-    def test_duration_expired_no_callback(self):
+    @mock.patch('oslo_utils.timeutils.now')
+    def test_duration_expired_no_callback(self, now):
+        now.return_value = 0
         t = common.DecayingTimer(2)
-        t._ends_at = time.time() - 10
-        remaining = t.check_return()
-        self.assertAlmostEqual(-10, remaining, 0)
+        t.start()
 
-    def test_duration_callback(self):
+        now.return_value = 3
+        remaining = t.check_return()
+        self.assertEqual(0, remaining)
+
+    @mock.patch('oslo_utils.timeutils.now')
+    def test_duration_callback(self, now):
+        now.return_value = 0
         t = common.DecayingTimer(2)
-        t._ends_at = time.time() - 10
+        t.start()
+
+        now.return_value = 3
         callback = mock.Mock()
         remaining = t.check_return(callback)
-        self.assertAlmostEqual(-10, remaining, 0)
+        self.assertEqual(0, remaining)
         callback.assert_called_once