EngineTimer: fix misuse of epsilon when firing timer (#399)

Due to rounding errors with floating-point numbers, we use an EPSILON
value for error margin, but it should be used only when comparing
input parameters, not when firing a timer.

Closes #399.

Change-Id: I8f056848c61b48dd59d91f44c09c9caf17c7fa58

Author: thiell

lib/ClusterShell/Engine/Engine.py

@@ -311,7 +311,7 @@ def fire_expired(self):
         # timer is fired, but only once per call.
         expired_timercases = []
         now = time.time()
-        while self.timers and (self.timers[0].fire_date - now) <= EPSILON:
+        while self.timers and self.timers[0].fire_date <= now:
             expired_timercases.append(heapq.heappop(self.timers))
             self._dequeue_disarmed()
 

tests/TaskTimerTest.py

@@ -428,17 +428,22 @@ def testForceDelayedRepeaterAutoClose(self):
         INTERVAL = 0.25
         task = task_self()
         teh = self.__class__.TForceDelayedRepeaterAutoCloseChecker()
-        bootstrap = task.shell("sleep %f" % INTERVAL)
+        bootstrap = task.shell("sleep %f" % (2 * INTERVAL))
         repeater1 = task.timer(INTERVAL, teh, INTERVAL, autoclose=True)
         repeater2 = task.timer(INTERVAL, teh, INTERVAL, autoclose=True)
         task.resume()
         # Expected behavior: both timers will fire after INTERVAL, the first
         # one will block thread for INTERVAL+0.1, the second one will also
         # block for INTERVAL+0.1 more time. Then at next runloop the engine
         # will see our shell command termination so will unregister associated
-        # worker client. At this point, only autoclosing timers remain
+        # worker client. At this point, only non-autoclosing timers remain
         # registered, so timer firing will be skipped and runloop will exit.
-        self.assertEqual(teh.count, 2)
+        #
+        # Why two possible values below? This has changed due to #399:
+        # count will be 1 if one timer is fired first (most likely without
+        #   epsilon batching effect fixed in #399)
+        # count will be 2 if both timers are fired during the same runloop
+        self.assertTrue(teh.count in (1, 2))
 
     def testMultipleAddSameTimerPrivate(self):
         """test multiple add() of same timer [private]"""