micro-optimize no timer case

cassandra/connection.py

@@ -973,10 +973,12 @@ class TimerManager(object):
         :return: next end time, or None
         """
         queue = self._queue
+        if self._new_timers:
             new_timers = self._new_timers
             while new_timers:
                 heappush(queue, new_timers.pop())
 
+        if queue:
             now = time.time()
             while queue:
                 try:
@@ -994,11 +996,3 @@ class TimerManager(object):
             return self._queue[0][0]
         except IndexError:
             pass
-
-    @property
-    def next_offset(self):
-        try:
-            next_end = self._queue[0][0]
-            return next_end - time.time()
-        except IndexError:
-            pass

cassandra/io/libevreactor.py

@@ -19,6 +19,7 @@ import os
 import socket
 import ssl
 from threading import Lock, Thread
+import time
 import weakref
 
 from six.moves import range
@@ -144,9 +145,9 @@ class LibevLoop(object):
 
     def _update_timer(self):
         if not self._shutdown:
-            self._timers.service_timeouts()
+            next_end = self._timers.service_timeouts()
-            offset = self._timers.next_offset or 100000  # none pending; will be updated again when something new happens
+            if next_end:
-            self._loop_timer.start(offset)
+                self._loop_timer.start(next_end - time.time())  # timer handles negative values
         else:
             self._loop_timer.stop()