You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
116 lines
3.1 KiB
116 lines
3.1 KiB
#!/usr/bin/python
|
|
# -*- coding: utf-8 -*-
|
|
|
|
from __future__ import absolute_import, division, print_function, \
|
|
with_statement
|
|
|
|
import collections
|
|
import logging
|
|
import time
|
|
|
|
|
|
# this LRUCache is optimized for concurrency, not QPS
|
|
# n: concurrency, keys stored in the cache
|
|
# m: visits not timed out, proportional to QPS * timeout
|
|
# get & set is O(1), not O(n). thus we can support very large n
|
|
# TODO: if timeout or QPS is too large, then this cache is not very efficient,
|
|
# as sweep() causes long pause
|
|
|
|
|
|
class LRUCache(collections.MutableMapping):
|
|
"""This class is not thread safe"""
|
|
|
|
def __init__(self, timeout=60, close_callback=None, *args, **kwargs):
|
|
self.timeout = timeout
|
|
self.close_callback = close_callback
|
|
self._store = {}
|
|
self._time_to_keys = collections.defaultdict(list)
|
|
self._keys_to_last_time = {}
|
|
self._last_visits = collections.deque()
|
|
self.update(dict(*args, **kwargs)) # use the free update to set keys
|
|
|
|
def __getitem__(self, key):
|
|
# O(1)
|
|
t = time.time()
|
|
self._keys_to_last_time[key] = t
|
|
self._time_to_keys[t].append(key)
|
|
self._last_visits.append(t)
|
|
return self._store[key]
|
|
|
|
def __setitem__(self, key, value):
|
|
# O(1)
|
|
t = time.time()
|
|
self._keys_to_last_time[key] = t
|
|
self._store[key] = value
|
|
self._time_to_keys[t].append(key)
|
|
self._last_visits.append(t)
|
|
|
|
def __delitem__(self, key):
|
|
# O(1)
|
|
del self._store[key]
|
|
del self._keys_to_last_time[key]
|
|
|
|
def __iter__(self):
|
|
return iter(self._store)
|
|
|
|
def __len__(self):
|
|
return len(self._store)
|
|
|
|
def sweep(self):
|
|
# O(m)
|
|
now = time.time()
|
|
c = 0
|
|
while len(self._last_visits) > 0:
|
|
least = self._last_visits[0]
|
|
if now - least <= self.timeout:
|
|
break
|
|
if self.close_callback is not None:
|
|
for key in self._time_to_keys[least]:
|
|
if self._store.__contains__(key):
|
|
if now - self._keys_to_last_time[key] > self.timeout:
|
|
value = self._store[key]
|
|
self.close_callback(value)
|
|
for key in self._time_to_keys[least]:
|
|
self._last_visits.popleft()
|
|
if self._store.__contains__(key):
|
|
if now - self._keys_to_last_time[key] > self.timeout:
|
|
del self._store[key]
|
|
del self._keys_to_last_time[key]
|
|
c += 1
|
|
del self._time_to_keys[least]
|
|
if c:
|
|
logging.debug('%d keys swept' % c)
|
|
|
|
|
|
def test():
|
|
c = LRUCache(timeout=0.3)
|
|
|
|
c['a'] = 1
|
|
assert c['a'] == 1
|
|
|
|
time.sleep(0.5)
|
|
c.sweep()
|
|
assert 'a' not in c
|
|
|
|
c['a'] = 2
|
|
c['b'] = 3
|
|
time.sleep(0.2)
|
|
c.sweep()
|
|
assert c['a'] == 2
|
|
assert c['b'] == 3
|
|
|
|
time.sleep(0.2)
|
|
c.sweep()
|
|
c['b']
|
|
time.sleep(0.2)
|
|
c.sweep()
|
|
assert 'a' not in c
|
|
assert c['b'] == 3
|
|
|
|
time.sleep(0.5)
|
|
c.sweep()
|
|
assert 'a' not in c
|
|
assert 'b' not in c
|
|
|
|
if __name__ == '__main__':
|
|
test()
|
|
|