Flask url_for ignoring port

Question

I have a Flask app running on port 5000. My server admin has configured nginx to forward this to port 5001 (sorry if I have the wrong terminology: the Flask app is running on port 5000, but the app is publicly accessible at http://the_url:5001).

All routes accessed directly in the browser work, but any redirect using url_for() seem to result in the port being missed from the URL — i.e. redirect(url_for('index')) redirects to http://the_url/ rather than http://the_url:5001/ (where the @app.route("/") triggers the function index()).

How do I make sure Flask adds the correct port when redirecting? If I change the default port to 5001, the nginx configuration will not work as it expects the app to be runnning on port 5000?

Possible duplicate of [Where do I define the domain to be used by url\_for() in Flask?](http://stackoverflow.com/questions/12162634/where-do-i-define-the-domain-to-be-used-by-url-for-in-flask) — ahmed, Oct 14 '15 at 11:19
Read commentaries for answer in http://stackoverflow.com/questions/12162634/where-do-i-define-the-domain-to-be-used-by-url-for-in-flask. You should remove 'http' part from config. — Jimilian, Oct 14 '15 at 11:42
I'd seen previous answers, but setting the `app.config["SERVER_NAME"]` variable stops the site running ... unless I am doing this wrong? (I just set it to: `the_url:5001`) — user2672537, Oct 14 '15 at 12:35
@user2672537, you need to setup `SERVER_NAME` = `localhost:5001` — Jimilian, Oct 14 '15 at 17:42
What helped me was this url (it's old, but still worked): https://flask.palletsprojects.com/en/1.0.x/deploying/wsgi-standalone/#proxy-setups — colidyre, Jun 02 '20 at 15:13

score 19 · Answer 1 · edited May 23 '17 at 12:34

19

add this to your Nginx config: proxy_set_header Host $http_host; or proxy_set_header Host $host:5001

read here

edited May 23 '17 at 12:34

Community

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1

answered Feb 14 '17 at 01:55

jiayi Peng

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11

Also use url_for(x, _external=True) so that it construct the URL based on headers – hgasimov Aug 18 '19 at 14:51

score 0 · Answer 2 · answered Oct 14 '15 at 17:38

Try adding something like this to the nginx config.

location / {
            proxy_pass http://localhost:5000;

            proxy_set_header X-Real-IP $remote_addr;
            proxy_set_header Host $host;
            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;

            proxy_set_header X-NginX-Proxy true;
        }

This way you can have your flask app running on localhost:5000. If you set up your server { listen 80; } config correctly (at the top of the config) the user should be able to hit port 80 and it will redirect to internal 5000 port. All my url_for() work perfectly.

Flask url_for ignoring port

2 Answers2