nginx sites-enabled file for generic rails project using unicorn

unicorn.conf

upstream unicorn_server {
        # This is the socket we configured in unicorn.rb
        server unix:/srv/www/example/shared/sockets/unicorn.sock fail_timeout=0;
}

server{
        listen 80 default;
        server_name example;
        root /srv/www/example/current/public;
        try_files $uri/index.html $uri.html $uri @unicorn;
        underscores_in_headers on;

        location @unicorn {
                
                # lock down hosts
                if ($host !~ ^(example.com)$ ) {
                  return 444;
                }

                proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
                proxy_set_header ACCESS_ID $http_access_id;

                proxy_set_header Access-ID2 $http_access_id;
                proxy_set_header Host $http_host;

                proxy_redirect off;

                proxy_pass http://unicorn_server;
        }

        # example of redirecting to an external blog
        #location /blog/ {
        #    proxy_pass http://example.com/blog/;
        #
        #    proxy_read_timeout 600;
        #
        #    proxy_set_header X-Real-IP 173.254.28.119;
        #    proxy_set_header Host $host;
        #    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        #}

        error_page 500 502 503 504 /500.html;
        location = /500.html {
                root /srv/www/example/current/public;
        }
}