Giovanni Di Milia Giovanni Di Milia - 2 years ago 121
Python Question

Decide when to refresh OAUTH2 token with Python Social Auth

I believe this is mostly a question about best practices.

I have an OAUTH2 provider that issues access tokens (valid for 10 hours) as long as refresh tokens.

I found here that it is pretty easy to refresh the access token but I cannot understand how to decide when it is time to refresh.

The easy answer is probably "when it does not work any more", meaning when I get a HTTP 401 from the backend.
The problem with this solution is that it is not that efficient, plus I can only assume I got a 401 because the token has expired.

I my django app I found that the

user social auth
has an
Extra data
field containing something like this:

"scope": "read write",
"expires": 36000,
"refresh_token": "xxxxxxxxxxxxx",
"access_token": "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx",
"token_type": "Bearer"

but I am not sure how to use the

So my question is: how do I know if an access token has expired and I need to refresh it?

I just found this comment that seems relevant, but I cannot understand how to plug this new function in the pipeline in order to work during the token refresh.

Answer Source

I eventually figured this out. The reason I was initially confused was because there are actually two cases:

  1. When the user comes from a login, so when basically the pipeline get executed.
  2. When the token is refreshed calling the user social auth method refresh_token

To solve the first case

I created a new function for the pipeline:

def set_last_update(details, *args, **kwargs):  # pylint: disable=unused-argument
    Pipeline function to add extra information about when the social auth
    profile has been updated.
        details (dict): dictionary of informations about the user
        dict: updated details dictionary
    details['updated_at'] = datetime.utcnow().timestamp()
    return details

in the settings I added it in the pipeline right before the load_extra_data

    # the following custom pipeline func goes before load_extra_data

and, still in the settings I added the new field in the extra data.


For the second case:

I overwrote the refresh_token method of my backend to add the extra field.

def refresh_token(self, token, *args, **kwargs):
    Overridden method to add extra info during refresh token.
        token (str): valid refresh token
        dict of information about the user
    response = super(EdxOrgOAuth2, self).refresh_token(token, *args, **kwargs)
    response['updated_at'] = datetime.utcnow().timestamp()
    return response

Still in the backend class, I added an extra field to extract the expires_in field coming from the server.

    ('refresh_token', 'refresh_token', True),
    ('expires_in', 'expires_in'),
    ('token_type', 'token_type', True),
    ('scope', 'scope'),

At this point I have the timestamp when the access token has been created (updated_at) and the amount of seconds it will be valid (expires_in).

NOTE: the updated_at is an approximation, because it is created on the client and not on the provider server.

Now the only thing missing is a function to check if it is time to refresh the access token.

def _send_refresh_request(user_social):
    Private function that refresh an user access token
    strategy = load_strategy()
    except HTTPError as exc:
        if exc.response.status_code in (400, 401,):
            raise InvalidCredentialStored(
                message='Received a {} status code from the OAUTH server'.format(

def refresh_user_token(user_social):
    Utility function to refresh the access token if is (almost) expired
        user_social (UserSocialAuth): a user social auth instance
        last_update = datetime.fromtimestamp(user_social.extra_data.get('updated_at'))
        expires_in = timedelta(seconds=user_social.extra_data.get('expires_in'))
    except TypeError:
    # small error margin of 5 minutes to be safe
    error_margin = timedelta(minutes=5)
    if datetime.utcnow() - last_update >= expires_in - error_margin:

I hope this can be helpful for other people.

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