nginx/gunicorn connection hanging for 60 seconds

Question

I'm doing a HTTP POST request against a nginx->gunicorn->Django app. Response body comes back quickly, but the request doesn't finish completely for about 60 more seconds.

By "finish completely" I mean that various clients I've tried (Chrome, wget, Android app I'm building) indicate that request is still in progress, as if waiting for more data. Listening in from Wireshark I see that all data arrives quickly, then after 60 seconds ACK FIN finally comes.

The same POST request on local development server ( ./manage.py runserver ) executes quickly. Also, it executes quickly against gunicorn directly, bypassing nginx. Also works quickly in Apache/mod_wsgi setup.

GET requests have no issues. Even other POST requests are fine. One difference I'm aware of is that this specific request returns 201 not 200.

I figure it has someting to do with Content-Length headers, closed vs keepalive connections, but don't yet know how things are supposed to work correctly.

• Backend server (gunicorn) is currently closing connections, this makes sense.
• Should backend server include Content-Length header , or Transfer-encoding: chunked ? Or should nginx be able to cope without these, and add them as needed?
• I assume connection keep-alive is good to have, and should not be disabled in nginx.

Update: Setting keepalive_timeout to 0 in nginx.conf fixes my problem. But, of course, keep-alive is gone. I'm still not sure what's the issue. Probably something in the stack (my Django app or gunicorn) doesn't implement chunked transfer correctly, and confuses clients.

Answer 1

It sounds like your upstream server (gunicorn) is somehow holding the connection open on that specific api call - I don't know why (depends on your code, I think), but the default proxy_read_timeout option in nginx is 60 seconds, so it sounds like this response isn't being received, for some reason.

I use a very similar setup and I don't notice any issues on POSTs generally, or any other requests.

Note that return HttpResponse(status=201) has caused me issues before - it seems Django prefers an explicitly empty body: return HttpResponse("", status=201) to work. I usually set something in the body where I'm expected to - this may be something to watch out for.