Account for tasks duration in LoopingCall delay

Fixes bug 1079725

Previously the time spent executing tasks was not accounted for
when determining how much time to sleep between task runs.

Now we subtract the duration of the last tasks run from the next
sleep interval.

Change-Id: I4b3e27d4aaa21d020159d46eea40bdd80361cea7

1 files changed, 40 insertions, 8 deletions

diff --git a/tests/unit/test_loopingcall.py b/tests/unit/test_loopingcall.py
index 11aa7e3..8307a11 100644
--- a/tests/unit/test_loopingcall.py
+++ b/tests/unit/test_loopingcall.py
@@ -14,9 +14,14 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
+import datetime
 import unittest
 
+from eventlet import greenthread
+import mox
+
 from openstack.common import loopingcall
+from openstack.common import timeutils
 
 
 class LoopingCallTestCase(unittest.TestCase):
@@ -38,15 +43,42 @@ class LoopingCallTestCase(unittest.TestCase):
         timer = loopingcall.LoopingCall(_raise_it)
         self.assertFalse(timer.start(interval=0.5).wait())
 
+    def _wait_for_zero(self):
+        """Called at an interval until num_runs == 0."""
+        if self.num_runs == 0:
+            raise loopingcall.LoopingCallDone(False)
+        else:
+            self.num_runs = self.num_runs - 1
+
     def test_repeat(self):
         self.num_runs = 2
 
-        def _wait_for_zero():
-            """Called at an interval until num_runs == 0."""
-            if self.num_runs == 0:
-                raise loopingcall.LoopingCallDone(False)
-            else:
-                self.num_runs = self.num_runs - 1
-
-        timer = loopingcall.LoopingCall(_wait_for_zero)
+        timer = loopingcall.LoopingCall(self._wait_for_zero)
         self.assertFalse(timer.start(interval=0.5).wait())
+
+    def test_interval_adjustment(self):
+        """Ensure the interval is adjusted to account for task duration"""
+        self.num_runs = 3
+
+        now = datetime.datetime.utcnow()
+        second = datetime.timedelta(seconds=1)
+        smidgen = datetime.timedelta(microseconds=10000)
+        timeoverrides = [now, now + second - smidgen,
+                         now, now + second + second,
+                         now, now + second + smidgen]
+
+        m = mox.Mox()
+        m.StubOutWithMock(greenthread, 'sleep')
+        greenthread.sleep(mox.IsAlmost(0.02))
+        greenthread.sleep(mox.IsAlmost(0.0))
+        greenthread.sleep(mox.IsAlmost(0.0))
+        m.ReplayAll()
+
+        try:
+            timeutils.set_time_override(timeoverrides)
+            timer = loopingcall.LoopingCall(self._wait_for_zero)
+            timer.start(interval=1.01).wait()
+        finally:
+            timeutils.clear_time_override()
+            m.UnsetStubs()
+            m.VerifyAll()