如何保持龙卷风呼叫异步？

Question

While doing an async mongodb query like the one in the below class how is this call really non-blocking if I still have access to an argument like self.get_argument("ip_address") inside the callback function? Or should I not access to the argument like this to keep the call async?

class MainHandler(tornado.web.RequestHandler):
    def get(self):
        app_key = self.get_argument("app_key")

        #async call to mongodb. call _valid_app afterwards
        db.apps.find_one({'app_key': app_key}, callback=self._valid_app);

    def _valid_app(self, response, error):
       if error:
           raise tornado.web.HTTPError(500)

       if response:
           ip_address = self.get_argument("ip_address")
           #rest of the code
       else:
           print("invalid app_key")

Answer 1

The instance self referenced in the callback function will be hanging around until the end of the callback function, therefore self.arguments will always be available inside _valid_app .

Maybe you can be confused by what would happen if another request to the same handler were made during the async call to Mongo. This would not be a problem because, for any new request a new instance of MainHandler is created, not interfering with the previous one.