gistfile1.txt

        upstream thin {
          server unix:/tmp/thin.0.sock;
          server unix:/tmp/thin.1.sock;
          server unix:/tmp/thin.2.sock;
        }

        server {
          listen 80;

          location /status.html {
            proxy_pass http://thin;
          }

          if ($http_x_forwarded_proto = 'http') {
            rewrite ^/(.*)$ https://$server_name$request_uri? permanent;
          }

          location / {
            proxy_pass http://thin;
          }

https://gist.github.com/4386980