How to force logout when Knox created token has expired?

I developed my Django based webapp with token authentication by following this tutorial of Brad Traversy (https://www.youtube.com/watch?v=0d7cIfiydAc) using Knox for authentication and React/Redux for the frontend. Login/logout works fine (here is Brad's code: https://github.com/bradtraversy/lead_manager_react_django/blob/master/leadmanager/frontend/src/actions/auth.js --> logout using a POST request), besides one issue: When the user stays away from the computer for a long time, the token expires in the meanwhile. So when the user returns they are still in the logged in zone of the website, but as soon as they open a React component with data loading from the DB a 401 error is thrown in the console ("Failed to load resource: the server responded with a status of 401 (Unauthorized)"). Then the user has to go on "logout" and login again.

This is not optimal, I would prefer that after the user returns, the system realizes the token expiry and logs the user automatically out. I have thought of the following approaches, but I am not sure how to implement it or which one is best:

1. For every API request: if the answer is 401 --> logout (this might also log the user out in case the token has not expired, but if there is some other permission problem) - seems not optimal to me.

2. Instead one could also create a testing route e.g. api/auth/check with a Django view including the typical check

   permission_classes = [permissions.IsAuthenticated]

and if 401 returned --> logout. So that would mean for every database request I have another rather unspecific database request before.

3. Check at every API request specifically if the token has expired --> how to do it? In the docs (https://james1345.github.io/django-rest-knox/) I couldn't find a method to check token validity. I see in the database table "knox_authtoken" an expiry date and a huge code in the column "digest", but this is obviously encrypted data and cannot be compared with the token value that one has in the browser under local storage.

I would be glad to receive recommendations on how to best implement this!

Jazzy's answer - option 3 - brought me on the right way (thank you!), but working with timers on the frontend side, was initially not successful, since starting a timer within a React component would only run as long as this component is visible. I have no component that is visible all the time of the user session. I changed the expiry duration of the token within Django settings from default value of 8 hours to 72 hours and implemented an idle check on the frontend with this package: https://www.npmjs.com/package/react-idle-timer . So as soon as my application is not used for 2 hours I call the logout action (api/auth/logout). With this approach I don't need to care about the expiry time of the token on Django side, since no user will be active throughout 72 hours. As soon as he logs in again, he will receive a new token.

New solution: I decided to not bother users too often with logging in and found this nice strategy:

• we choose to never expire Knox tokens
• we set expiry date for Django session to 90 days from last login
• if user does not log in for > 90 days, he will make at some point a request to the backend (e.g. data requests), there we include a check if the session data is available

if 'some_session_variable' in request.session:
    # whatever logic you need
else:
    return HttpResponse("logout")

Since session variable will not be available after the expiry the 'logout' string is returned. On the frontend we check every response for 'logout' string. If it is being returned we initiate the logout process. The idle timer is not used anymore (as it is not so reliable in my experience).