import time
class memcached_queue_context():
"A context manager for queuing operations per key via memcached"
poll_interval = 0.005 # in seconds
def __init__(self, memcache_client, key_base):
self.mc = memcache_client
self.key_base = key_base
self.queue_push_key = self.key_base + "-push"
self.queue_wait_key = self.key_base + "-wait"
def __enter__(self):
# initialize the queues if needed
self.mc.add(self.queue_push_key, '1')
self.mc.add(self.queue_wait_key, '1')
# take a number
index = self.mc.incr(self.queue_push_key) - 1
# poll the queue until your number comes up
while True:
idx = int(self.mc.get(self.queue_wait_key)) # int() is critical!!!
if not idx < index:
break
time.sleep(self.poll_interval)
return
def __exit__(self, exc_type, exc_val, exc_tb):
# advance the queue
self.mc.incr(self.queue_wait_key)
return False
