A snippet for https://t.me/nginx_ru #3

events {}

error_log /var/log/nginx/error.log debug;

http {
    # Add CORS headers for all requests
    add_header 'Access-Control-Allow-Origin' '*' always;
    add_header 'Access-Control-Allow-Methods' 'GET, POST, OPTIONS' always;
    add_header 'Access-Control-Allow-Headers' 'DNT,User-Agent,X-Requested-With,If-Modified-Since,Cache-Control,Content-Type,Range,Authorization' always;

    map $http_x_proxy_port $xproxyport {
        default 80;  # Default port if X-PROXY-PORT header is not set
        ~^[0-9]+$ $http_x_proxy_port;  # Use the value of X-PROXY-PORT if it is a number
    }

    log_format custom_debug 'Host: $host, Container: $container, Port: $xproxyport, Path: $uri, X-PROXY-PORT: $http_x_proxy_port, complete proxying URL will be: http://$container:$xproxyport$rest_of_path';
    access_log /var/log/nginx/access.log custom_debug;

    server {

        listen 80;
        http2 on;
        server_name proxy;

        resolver 127.0.0.11;

        location / {
            root /usr/share/nginx/html;
            index index.html;

            proxy_set_header Host $host;
            proxy_set_header X-Real-IP $proxy_protocol_addr;
            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
            proxy_set_header X-Forwarded-Proto $scheme;

            if ($request_method = OPTIONS) {
                add_header 'Content-Type' 'text/plain; charset=utf-8';
                add_header 'Content-Length' 0;
                return 204;
            }
        }

        location ~ ^/proxy/([^/]+)(/.*)?$ {
            # Extract container name from the URL
            set $container $1;
            set $rest_of_path $2;


            if ($request_method = OPTIONS) {
                add_header 'Content-Type' 'text/plain; charset=utf-8';
                add_header 'Content-Length' 0;
                return 204;
            }

            # Proxy the request to the respective container and port
            proxy_pass http://$container:$xproxyport$rest_of_path;
            proxy_set_header Host "0.0.0.0";
            proxy_set_header X-Real-IP $remote_addr;
            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
            proxy_set_header X-Forwarded-Proto $scheme;
        }
    }
}