如何在 GAE 任务队列中执行需要 OAuth 的操作？

Question

我有一个简单的 Google App Engine 应用，其中包含一个更新 YouTube 播放列表的 /update 页面。它看起来像这样：

class UpdatePage(webapp2.RequestHandler):

    @decorator.oauth_required
    def get(self):
        update_result = self.update_playlist()
        ...

routes = [('/update', UpdatePage),
          (decorator.callback_path, decorator.callback_handler())]
app = webapp2.WSGIApplication(routes, debug=True)

它按预期工作，update_playlist() 方法完成了它的工作，但事实证明，在某些情况下它可以运行很长时间，导致DeadlineExceededError。因此，在阅读了可用选项之后，我认为 Task Queue API 是可行的方法（对吗？），我正在尝试使用它，遵循 Using Push Queues in Python 指南。

→ 简而言之，我将UpdatePage 拆分为UpdatePageHandler + UpdatePageWorker：

class UpdateHandlerPage(webapp2.RequestHandler):

    @decorator.oauth_required
    def get(self):
        taskqueue.add(url='/updateworker')

class UpdateWorkerPage(webapp2.RequestHandler):

    def post(self):
        update_result = self.update_playlist()
        ...

routes = [('/update', UpdateHandlerPage),
          ('/updateworker', UpdateWorkerPage),
          (decorator.callback_path, decorator.callback_handler())]
app = webapp2.WSGIApplication(routes, debug=True)

不幸的是，在拆分之后，我的 OAuth2 装饰器似乎不再起作用：

INFO     2013-05-30 17:08:53,971 discovery.py:709] URL being requested: https://www.googleapis.com/youtube/v3/playlists?alt=json&part=snippet%2Cstatus
WARNING  2013-05-30 17:08:53,975 urlfetch_stub.py:480] Stripped prohibited headers from URLFetch request: ['content-length']
INFO     2013-05-30 17:08:54,351 client.py:493] Refreshing due to a 401
INFO     2013-05-30 17:08:54,361 appengine.py:276] make: Got type <class 'google.appengine.api.datastore_types.Blob'>
INFO     2013-05-30 17:08:54,363 appengine.py:289] validate: Got type <class 'oauth2client.client.OAuth2Credentials'>
INFO     2013-05-30 17:08:54,364 client.py:680] Refreshing access_token
INFO     2013-05-30 17:08:54,746 client.py:699] Failed to retrieve access token: {
  "error" : "invalid_grant"
}
INFO     2013-05-30 17:08:54,757 appengine.py:276] make: Got type <class 'google.appengine.api.datastore_types.Blob'>
INFO     2013-05-30 17:08:54,759 appengine.py:289] validate: Got type <class 'oauth2client.client.OAuth2Credentials'>
INFO     2013-05-30 17:08:54,761 appengine.py:289] validate: Got type <class 'oauth2client.client.OAuth2Credentials'>
INFO     2013-05-30 17:08:54,762 appengine.py:265] get: Got type <class 'oauth2client.appengine.CredentialsModel'>

如果不是装饰UpdateHandlerPage:get，而是装饰UpdateWorkerPage:post，我会得到一个无限失败循环：

INFO     2013-05-30 17:24:31,307 discovery.py:190] URL being requested: https://www.googleapis.com/discovery/v1/apis/youtube/v3/rest?userIp=127.0.0.1
INFO     2013-05-30 17:24:34,960 dev_appserver.py:3105] "GET /update HTTP/1.1" 200 -
INFO     2013-05-30 17:24:35,060 dev_appserver.py:3105] "POST /updateworker HTTP/1.1" 302 -
WARNING  2013-05-30 17:24:35,065 taskqueue_stub.py:1980] Task task1 failed to execute. This task will retry in 0.100 seconds
INFO     2013-05-30 17:24:35,240 dev_appserver.py:3105] "POST /updateworker HTTP/1.1" 302 -
WARNING  2013-05-30 17:24:35,245 taskqueue_stub.py:1980] Task task1 failed to execute. This task will retry in 0.200 seconds
...

我能做什么？感谢您的帮助！

Answer 1

由于任务队列任务将由您的应用程序生成，因此您的原始请求中的任何标头都不会被发送。特别是，Cookies 标头通过您的应用程序的 SACSID cookie 识别您的用户（由 App Engine 用户 API 提供）。

更新：（这是在原始帖子之后添加的。）由于没有 cookie，标识用户的 SACSID cookie 将不存在，因此 decorator.oauth_required 名称将每次在 cron 作业运行时强制重定向（即 HTTP 302）。

您最好将 App Engine 用户 ID 传递给您的任务，而不是尝试从装饰器中获取当前用户。首先获取当前用户（在您的装饰方法中）：

from google.appengine.api import users
# Guaranteed not to be None by the decorator
current_user = users.get_current_user()

然后在任务中传递 App Engine 用户 ID

import urllib
query_string = urllib.urlencode({'user_id': current_user.user_id()})
taskqueue.add(url='/updateworker?' + query_string)

然后在你的任务中，你可以检索到 user_id

# This is the 'user_id' you appended in the query string
user_id = self.request.get('user_id')

并使用它来获取该用户的凭据as is done in the decorator：

from oauth2client.appengine import CredentialsModel
from oauth2client.appengine import StorageByKeyName
# This assumes you are using the defaults for OAuth2Decorator,
# which your above code is
credentials = StorageByKeyName(
    CredentialsModel, user_id, 'credentials').get()