Flask API & nginx alongside each other - nginx

Question

I have a server that I'm trying to set up. I have a Flask server that needs to run on api.domain.com, while I have other subdomains pointing to the server. I have one problem. 2/3 subdomains have no problem using nginx. Meanwhile, my script tries to bind to port 80 on the same machine, therefore failing. Is there a way I can bind my Flask REST script to port 80 ONLY for the subdomain 'api'?
My current config is:
server {
server_name api.domain.me;
location / {
error_page 404 /404.html;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header X-Forwarded-Proto $http_x_forwarded_proto;
proxy_http_version 1.1;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection "upgrade";
proxy_max_temp_file_size 0;
proxy_pass http://127.0.0.1:5050/;
proxy_cache off;
proxy_read_timeout 240s;
}
}
There's a little problem though, nginx likes to turn all POST requests into GET requests, any ideas?
Thanks!

Answer 1

There is no way binding two different applications on port 80 at the same time.
I would set up your api like this:
Bind your Flask API to Port 8080.
On NGINX you can configure you subdomain pointing to your Flask Application
upstream flask_app {
server 127.0.0.1:8080;
}
sever {
listen 80;
server_name api.domain.com;
location / {
proxy_pass http://flask_app/;
proxy_set_header Host $host;
}
}

Answer 2

I actually found out after a bit of diagnosis.
server {
if ($host = api.domain.me) {
return 301 https://$host
}
# managed by Certbot
had to become:
server {
if ($host = api.domain.me) {
return 497 '{"code":"497", "text": "The client has made a HTTP request to a port listening for HTTPS requests"}';
}
Because Certbot tries to upgrade the request to https but the HTTP method gets changed to GET because of the 301 response code.