在django-xadmin中APScheduler的启动初始化实例

class StartupMiddleware(object):
 def __init__(self):
  #启动后台任务APScheduler
  init_scheduler()
 
  from django.core.exceptions import MiddlewareNotUsed
  raise MiddlewareNotUsed #TIP 抛出此异常，则Django将从 middleware 栈中移出该 middleware，请求就不会经过此middleware
 
 def process_request(self, request):
  print("*****enter startup middleware")

scheduler = None
def init_scheduler():
 global scheduler
 lock = threading.Lock() # TIP 多线程同步代码
 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),#线程模式下进程池大小
   'processpool': ProcessPoolExecutor(5),#进程模式下进程池大小
  }
  job_defaults = {
   'coalesce': True, #如果有几次未执行，条件可以时是否只执行一次
   'max_instances': 1, #同一个job同一时间最多有几个实例再跑
  }
 
  scheduler = BackgroundScheduler(executors=executors, job_defaults=job_defaults, timezone=timezone(TIME_ZONE))
 
  scheduler.add_job(...)
  scheduler.start()
  return scheduler