python 实现 redis 分布式锁

from contextlib import contextmanager
from random import random

DEFAULT_EXPIRES = 15
DEFAULT_RETRIES = 5

@contextmanager
def dist_lock(key, client):
key = 'lock_%s' % key

try:
t = _acquire_lock(key, client)
yield t
finally:
_release_lock(key, client)

def ask_lock(key,client):
key = 'lock_%s' % key
if client.get(key):
return True
else:
return False

def _acquire_lock(key, client):
while 1:
get_stored = client.get(key)
if get_stored:
time.sleep(0.03)
else:
if client.setnx(key, 1):
client.expire(key,DEFAULT_EXPIRES)
return True
return False

def _release_lock(key, client):
client.delete(key)