How to configure proxying in nginx depending on dns?

Question

Nginx

Good afternoon!
There is a proxy server (proxy-01) with such dns dev.example.com test.example.com preprod.example.com. With proxy-01, requests come to app-01/app-02 (dev/test/preprod sites here) all sites have the same locations, but different root_documents.
I know how to resolve proxying using upstreams by hanging sites on different ports.
The question is how to do it all on one port?
Thank you!

Answer 1

From what I understand, you need something like this:

server {
        listen 80;
        server_name app.example.com;

        location / {
                proxy_pass http://app-01/;
        }
}

server {
        listen 80;
        server_name preprod.example.com;

        location / {
                proxy_pass http://app-02/;
        }
}

Answer 2

Guys Pavel Mezhuev ky0 Alexey Ten , thank you!
Below is an example config. For each site, a separate
nginx-proxy config

upstream dev {
    server 172.17.1.1;
}

server {

        listen       80;
        server_name  dev.example.com;
        client_max_body_size 32m;


        server_name_in_redirect off;

        gzip on;
        gzip_types text/plain text/css application/json application/x-javascript text/xml application/xml application/xml+rss text/javascript application/javascript;



        location / {
            proxy_set_header Host $host;
            proxy_set_header X-Forwarded-Host $host;
            proxy_set_header X-Forwarded-Server $host;
            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
            proxy_set_header X-Real-IP $remote_addr;
            proxy_pass http://dev;

        }
}

nginx app

server {

        listen       80;
        server_name  dev.example.com;

        set $app_dir "/opt/app/dev/app";

        root $app_dir;
        index index.html;
        client_max_body_size 32m;

        access_log "/var/log/nginx/dev.access.log";
        error_log "/var/log/nginx/dev.error.log";


        location / {
        	root $app_dir;
            index index.html;
            add_header 'X-XSS-Protection' "1; mode=block;";
            try_files $uri $uri/ /index.html =404;
        }
}