python - 提取涉及 tornado.gen.Task 的异步代码

Question

我有许多 tornado.web.RequestHandler 类，它们使用 ID 和访问 key 安全 cookie 测试授权访问。我使用 gen.Task 通过内联回调异步访问 mongodb。由于其异步性，我无法找到一种方法来分解重复代码。我该怎么做？

class MyHandler(RequestHandler):
    @tornado.web.asynchronous
    @gen.engine
    def get(self):
        id = self.get_secure_cookie('id', None)
        accesskey = self.get_secure_cookie('accesskey', None)
        if not id or not accesskey:
            self.redirect('/a_public_area')
            return
        try:
            # convert to bson id format to access mongodb
            bson.objectid.ObjectId(id)
        except:
            # if not valid object id
            self.redirect('/a_public_area')
            return
        found_id, error = yield gen.Task(asyncmong_client_inst.collection.find_one, 
            {'_id': id, 'accesskey': accesskey}, fields={'_id': 1})
        if error['error']:
            raise HTTPError(500)
            return
        if not found_id[0]:
            self.redirect('/a_public_area')
            return

        # real business code follows

我想将上述因素纳入一个可能产生 HTTP 状态代码的函数中。

Answer 1

Tornado 有装饰器@tornado.web.authenticated。让我们使用它。

class BaseHandler(RequestHandler):
   def get_login_url(self):
        return u"/a_public_area"

    @gen.engine #Not sure about this step
    def get_current_user(self):
        id = self.get_secure_cookie('id', None)
        accesskey = self.get_secure_cookie('accesskey', None)
        if not id or not accesskey:
            return False

        #Are you sure need this? 
        try:
            # convert to bson id format to access mongodb
            bson.objectid.ObjectId(id)
        except:
            # if not valid object id
            return False

        #I believe that you don't need asynchronous mongo on auth query, so if it's not working - replace it with sync call
        found_id, error = yield gen.Task(asyncmong_client_inst.collection.find_one, 
            {'_id': id, 'accesskey': accesskey}, fields={'_id': 1})

        if error['error']:
            raise HTTPError(500)

        if not found_id[0]:
            return False

        return found_id


class MyHandler(BaseHandler):
    @tornado.web.asynchronous
    @tornado.web.authenticated
    @gen.engine
    def get(self):
        # real business code follows

到处使用 gen - 不是很好的做法。它可以把这个世界变成大意大利面。想想看。