Google App Engine / Drive SDK: catching a lot HTTP Deadline exceptions

Question

Our app is deployed on the Google App Engine, Python runtime (2.7) and is consuming the Drive API. More and more it catches HTTPException because of an exceeded deadline, on different endpoints (Drive, OAuth, etc.)

We have implemented an exponential back-off mechanism with 5 tries. Our app is more and more reaching this limit (this morning for example we had a lot of these exceptions).

What could be the origin of this issues? Is it possible to increase the timeout delay?

Thanks for your help.

Here's a full stacktrace (OAuth2 API):

2013-06-07 21:11:10,851 ERROR An error occurred : Deadline exceeded while waiting for HTTP response from URL: https://accounts.google.com/o/oauth2/token
Traceback (most recent call last):
  File "/python27_runtime/python27_lib/versions/third_party/webapp2-2.3/webapp2.py", line 545, in dispatch
    return method(*args, **kwargs)
  File "/base/data/home/apps/s~unishared-gae/production.367909734400765242/main.py", line 733, in get
    creds = self.GetCodeCredentials() or self.GetSessionCredentials()
  File "/base/data/home/apps/s~unishared-gae/production.367909734400765242/main.py", line 301, in GetCodeCredentials
    creds = oauth_flow.step2_exchange(code)
  File "lib/oauth2client/util.py", line 128, in positional_wrapper
    return wrapped(*args, **kwargs)
  File "lib/oauth2client/client.py", line 1283, in step2_exchange
    headers=headers)
  File "lib/httplib2/__init__.py", line 1570, in request
    (response, content) = self._request(conn, authority, uri, request_uri, method, body, headers, redirections, cachekey)
  File "lib/httplib2/__init__.py", line 1317, in _request
    (response, content) = self._conn_request(conn, request_uri, method, body, headers)
  File "lib/httplib2/__init__.py", line 1286, in _conn_request
    response = conn.getresponse()
  File "/python27_runtime/python27_dist/lib/python2.7/httplib.py", line 500, in getresponse
    raise HTTPException(str(e))

Answer 1

This blog post published in 2011 talks about how to catch DeadlineExceededError with metaclass instead of using decorators. I do not sure this guides or solves you, but gives you a idea that may be helpful.

from google.appengine.api import mail
from google.appengine.ext.deferred import defer
from google.appengine.ext.webapp import RequestHandler
from google.appengine.runtime import DeadlineExceededError
import sys
from traceback import format_exception
from SOME_APP_SPECIFIC_LIBRARY import serve_500
from LAST_POST import email_admins

class DecorateHttpVerbsMetaclass(type):

    def __new__(cls, name, bases, cls_attr):
        verbs = ['get', 'post', 'put', 'delete']
        for verb in verbs:
            if verb in cls_attr and isinstance(cls_attr[verb], function):
                cls_attr[verb] = deadline_decorator(cls_attr[verb])

        return super(DecorateHttpVerbsMetaclass, cls).__new__(cls, name,
                                                              bases, cls_attr)

class ExtendedHandler(RequestHandler):
    __metaclass__ = DecorateHttpVerbsMetaclass

    def handle_exception(self, exception, debug_mode):
        traceback_info = ''.join(format_exception(*sys.exc_info()))
        email_admins(traceback_info, defer_now=True)

        serve_500(self)