我有一些使用Celery线程的非常简单的定期代码。它只是打印“ Pre”和“
Post”，然后在它们之间睡眠。此链接的网站改编而成

from celery.task import task
from celery.task import periodic_task
from django.core.cache import cache
from time import sleep
import main
import cutout_score
from threading import Lock

import socket
from datetime import timedelta
from celery.decorators import task, periodic_task

def single_instance_task(timeout):
  def task_exc(func):
    def wrapper(*args, **kwargs):
        lock_id = "celery-single-instance-" + func.__name__
        acquire_lock = lambda: cache.add(lock_id, "true", timeout)
        release_lock = lambda: cache.delete(lock_id)
        if acquire_lock():
            try:
                func()
            finally:
                release_lock()
    return wrapper
  return task_exc

LOCK_EXPIRE = 60 * 5 # Lock expires in 5 minutes
@periodic_task(run_every = timedelta(seconds=2))
def test():
    lock_id = "lock"

    # cache.add fails if if the key already exists
    acquire_lock = lambda: cache.add(lock_id, "true", LOCK_EXPIRE)
    # memcache delete is very slow, but we have to use it to take
    # advantage of using add() for atomic locking
    release_lock = lambda: cache.delete(lock_id)

    if acquire_lock():
        try:
            print 'pre'
            sleep(20)
            print 'post'
        finally:
            release_lock()
        return
    print 'already in use...'

此代码 永不 打印'already in use...'; 使用@single_instance_task装饰器时也会发生相同的现象。

你知道怎么了吗

编辑：我简化了问题，以便它不会写入内存（使用全局或django缓存）； 我还是没看'already in use...'

编辑：当我将以下代码添加到我的Django settings.py文件中时（通过更改
https://docs.djangoproject.com/en/dev/topics/cache/中的代码，一切都按预期工作，
但仅当我使用port时11211 （奇怪的是，我的服务器在端口8000上）

CACHES = {
    'default': {
        'BACKEND': 'django.core.cache.backends.memcached.MemcachedCache',
        'LOCATION': [
            '127.0.0.1:11211'
        ]
    }
}