class StartupMiddleware(object):
 def __init__(self):
  #啟動后臺任務(wù)APScheduler
  init_scheduler()
 
  from django.core.exceptions import MiddlewareNotUsed
  raise MiddlewareNotUsed #TIP 拋出此異常，則Django將從 middleware 棧中移出該 middleware，請求就不會經(jīng)過此middleware
 
 def process_request(self, request):
  print("*****enter startup middleware")

scheduler = None
def init_scheduler():
 global scheduler
 lock = threading.Lock() # TIP 多線程同步代碼
 with lock:
  if scheduler and scheduler.running:
   print('*****APScheduler is already started, pid:{}, tid:{}'.format(os.getpid(), threading.current_thread().getName()))
   return scheduler
  executors = {
   'default': ThreadPoolExecutor(5),#線程模式下進程池大小
   'processpool': ProcessPoolExecutor(5),#進程模式下進程池大小
  }
  job_defaults = {
   'coalesce': True, #如果有幾次未執(zhí)行，條件可以時是否只執(zhí)行一次
   'max_instances': 1, #同一個job同一時間最多有幾個實例再跑
  }
 
  scheduler = BackgroundScheduler(executors=executors, job_defaults=job_defaults, timezone=timezone(TIME_ZONE))
 
  scheduler.add_job(...)
  scheduler.start()
  return scheduler