def _schedule_expiration (self):
""" Sets up a timer that will call _expire_old_connections when the
oldest connection currently in the free pool is ready to expire. This
is the earliest possible time that a connection could expire, thus, the
timer will be running as infrequently as possible without missing a
possible expiration.
If this function is called when a timer is already scheduled, it does
nothing.
If max_age or max_idle is 0, _schedule_expiration likewise does nothing.
"""
if self.max_age is 0 or self.max_idle is 0:
# expiration is unnecessary because all connections will be expired
# on put
return
if ( self._expiration_timer is not None
and not getattr(self._expiration_timer, 'called', False)):
# the next timer is already scheduled
return
try:
now = time.time()
self._expire_old_connections(now)
# the last item in the list, because of the stack ordering,
# is going to be the most-idle
idle_delay = (self.free_items[-1][0] - now) + self.max_idle
oldest = min([t[1] for t in self.free_items])
age_delay = (oldest - now) + self.max_age
next_delay = min(idle_delay, age_delay)
except (IndexError, ValueError):
# no free items, unschedule ourselves
self._expiration_timer = None
return
if next_delay > 0:
# set up a continuous self-calling loop
self._expiration_timer = Timer(next_delay, GreenThread(hubs.get_hub().greenlet).switch,
self._schedule_expiration, [], {})
self._expiration_timer.schedule()
