Detect, within single-page apps, if user has been logged out, and require re-login

[jamalex]

Context: A lot of interaction with the site now happens without page reloads (within a single-page app portion of the site, e.g. sidebar and content navigation/viewing). We only check logged-in status on first page load.

Expected: If the user gets logged out (via a timeout, or via logging out in a different tab), this should be detected ASAP and the user should be prompted to login.

Observed: User is still shown as logged in, but API requests start returning 403's or otherwise erroring out/doing funny stuff.

Possible solutions:

For detecting logouts:

• Less preferred: Detect 403's in API responses
• More preferred: Augment API requests with metadata regarding things like being logged out (in parallel with the tastypie-metadata-level response data, so these fields won't be loaded into the data).

For requiring logins:

• Less preferred: Redirect entire page to login page (at least setting the ?next param to bring them back after)
• More preferred: Popup a Backbone.js-driven login modal, which allows inline AJAX-based login without navigating and losing page state.

[jamalex]

#2939 was an initial (constrained) attempt at this, on the nalanda branch, but isn't general-purpose.

[anuragkanungo]

Would work on it soon.