Flask redirect(url_for) error with gunricorn + nginx

Question

I am having a problem with the redirect(url_for) function in my flask app.

Any redirect(url_for("index")) line redirects the application from domain.com/app to ip-addr/app, where the ip-addr is my own client machines ip, not the server's.

This has gotten me very confused, and I don't know where exactly the issue occurs, as it only happens on the server and not on any local testing.

Details:

I am using the reverse proxy setup found here http://flask.pocoo.org/snippets/35/. My nginx config is setup like so

location /app {
                proxy_set_header X-Script-Name /app;
                proxy_set_header Host $http_host;
                proxy_set_header X-Forwarded-Host $proxy_add_x_forwarded_for;
                proxy_redirect off;
                proxy_set_header X-Real-IP $remote_addr;
                proxy_set_header X-Scheme $scheme;
                proxy_connect_timeout 60;
                proxy_read_timeout 60;
                proxy_pass http://localhost:8000/;
        }

I have gunicorn running my flask app as a upstart task. Any hints?

EDIT:

So I dug around a bit and found that the this git report had similar issues, https://github.com/omab/django-social-auth/issues/157.

Nginx - Gunicorn serving to Nginx via localhost (127.0.0.1:1234). Unfortunately, when I authenticate with social platforms, the redirect URL social-auth is sending them to is 127.0.0.1:1234/twitter/complete, which obviously can't be resolved by the client's browser.

It seems my Flask app is not getting the memo to update its redirect routes.

Answer 1

I found a solution. I had to use redirect(url_for(location, _external=True)) for all my redirects.

It seems url_for(x, _external=True) will take all variables in my nginx proxy_set_header to construct the url, while the url_for(x) is not doing that.

This works for both server and local development.

Answer 2

Adding include proxy_params fixed it for me.

location / {
    proxy_pass http://...;
    include proxy_params;
}