SessionMiddleware support 503 status code

[SessionIssue]

Hi guys,

I have the following situation. In one of my applications I'm having an issue with returning the right status code.
For example I had this situation where I wanted to list 1000 results, this normally takes a couple of seconds, but during this request, my DB went offline or got stuck for some reason. Currently, this resulted in a 500 status code.
In the API client that interfaces with this code we want to return a 503 because of an external source that only retries tasks on specific status codes (like 503), The current SessionMiddleware hijacks the statuscode and makes it impossible to raise a Service Unavailable (503).

if response.status_code != 500:
                    try:
                        request.session.save()
                    except UpdateError:
                        raise SessionInterrupted(
                            "The request's session was deleted before the "
                            "request completed. The user may have logged "
                            "out in a concurrent request, for example."
                        )
                    response.set_cookie(
                        settings.SESSION_COOKIE_NAME,
                        request.session.session_key, max_age=max_age,
                        expires=expires, domain=settings.SESSION_COOKIE_DOMAIN,
                        path=settings.SESSION_COOKIE_PATH,
                        secure=settings.SESSION_COOKIE_SECURE or None,
                        httponly=settings.SESSION_COOKIE_HTTPONLY or None,
                        samesite=settings.SESSION_COOKIE_SAMESITE,
                    )

As my DB is offline, this results in a 400 error, as the session can't be saved. But this is incorrect, as the base request isn't a bad request.
I rewrote this small piece in a custom middleware that inherits the SessionMiddleware, but this is not a futureproof solution:

**if response.status_code not in [500, 503]:**
                    try:
                        request.session.save()
                    except UpdateError:
                        raise SessionInterrupted(
                            "The request's session was deleted before the "
                            "request completed. The user may have logged "
                            "out in a concurrent request, for example."
                        )
                    response.set_cookie(
                        settings.SESSION_COOKIE_NAME,
                        request.session.session_key, max_age=max_age,
                        expires=expires, domain=settings.SESSION_COOKIE_DOMAIN,
                        path=settings.SESSION_COOKIE_PATH,
                        secure=settings.SESSION_COOKIE_SECURE or None,
                        httponly=settings.SESSION_COOKIE_HTTPONLY or None,
                        samesite=settings.SESSION_COOKIE_SAMESITE,
                    )

It's a small change, but it will make it hard for us to keep track of all the Django updates.

Do you have a solution for this issue?

Thanks in advance.

[Mariusz Felisiak]

Thanks for this ticket, however it is a support question and Trac is not a support channel.

[Mariusz Felisiak]

I'm not sure why we should treat 503 differently. IMO, we could reconsider avoiding session saving when status code > 500 🤔

PS. Do not reopen tickets without further explanation.

[SessionIssue]

Replying to Mariusz Felisiak:

I'm not sure why we should treat 503 differently. IMO, we could reconsider avoiding session saving when status code > 500 🤔

PS. Do not reopen tickets without further explanation.

I assume you mean code >= 500 right?
That would fix the problem and seems like a convenient solution to me.
Thanks a lot! 😁

[Carlton Gibson]

Happy to look at a patch (with tests) adjusting the check to if response.status_code >= 500:

[SessionIssue]

Replying to Carlton Gibson:

Happy to look at a patch (with tests) adjusting the check to if response.status_code >= 500:

Is this a patch we can expect to see in 3.2 (LTS), or will this only be patched in the upcoming 4.2 LTS?
Thanks in advance.

[Abhinav Yadav]

​PR

[Mariusz Felisiak <felisiak.mariusz@…>]

In 17472c3:

Fixed #34173 -- Skipped saving sessions on 5xx responses.