Nginx proxy pass to localhost:3000 for development, suitable to put it in sites-available/

proxypass-site

upstream dev {
  server 127.0.0.1:3000;
}
    
server {
  listen       80;
      
  # You could put a server_name directive here (or multiple) if
  # you have not setup wildcard DNS for *.dev domains
  # See http://jessedearing.com/nodes/9-setting-up-wildcard-subdomains-on-os-x-10-6

  # If we choose a root, then we can't switch things around easily
  # Using /dev/null means that static assets are served through
  # Rails instead, which for development is okay
  root         /dev/null;

  index        index.html index.htm;
 
  try_files  $uri/index.html $uri.html $uri @dev;
 
  location @dev {
    proxy_set_header  X-Real-IP        $remote_addr;
    proxy_set_header  X-Forwarded-For  $proxy_add_x_forwarded_for;
    proxy_set_header  Host             $http_host;
    proxy_redirect    off;
    proxy_pass        http://dev;
  }
  error_page   500 502 503 504  /50x.html;
}