nginx configuration using cloudflare ip and nginx with-http_realip module

backend.conf

upstream app {
    # Path to Unicorn SOCK file, as defined previously
    server unix:/servers/sites/backend-saas/shared/tmp/sockets/.unicorn.sock fail_timeout=0;
}

server {
  listen 80;
  server_name passworks.io;
  return 301 $scheme://www.passworks.io$request_uri;
}

server {

    listen 80;
    server_name www.passworks.io;

    add_header X-UA-Compatible "IE=edge";

    # Application root, as defined previously
    root /servers/sites/backend-saas/current/public;

    try_files $uri/index.html $uri @app;

    client_max_body_size 10M;

    location @app {
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header Host $http_host;
        proxy_redirect off;
        proxy_pass http://app;

        #
        # Cloudflare IPV4 and IPV6 IP collection
        # make sure that you have nginx compiled with `with-http_realip_module` module
        # http://nginx.org/en/docs/http/ngx_http_realip_module.html
        # see if you have me module compiled using: nginx -V
        #
        # Updated list of IP's:
        # https://www.cloudflare.com/ips-v6
        # https://www.cloudflare.com/ips-v4
        #
        set_real_ip_from   199.27.128.0/21;
        set_real_ip_from   173.245.48.0/20;
        set_real_ip_from   103.21.244.0/22;
        set_real_ip_from   103.22.200.0/22;
        set_real_ip_from   103.31.4.0/22;
        set_real_ip_from   141.101.64.0/18;
        set_real_ip_from   108.162.192.0/18;
        set_real_ip_from   190.93.240.0/20;
        set_real_ip_from   188.114.96.0/20;
        set_real_ip_from   197.234.240.0/22;
        set_real_ip_from   198.41.128.0/17;
        set_real_ip_from   162.158.0.0/15;
        set_real_ip_from   104.16.0.0/12;
        set_real_ip_from   2400:cb00::/32;
        set_real_ip_from   2606:4700::/32;
        set_real_ip_from   2803:f800::/32;
        set_real_ip_from   2405:b500::/32;
        set_real_ip_from   2405:8100::/32;
        real_ip_header     CF-Connecting-IP;

    }

    location ~ ^/(assets|images|javascripts|stylesheets|swfs|system)/ {
          gzip_static       on;
          expires           max;
          add_header        Cache-Control public;
          add_header        Last-Modified "";
          add_header        ETag "";

          open_file_cache          max=1000 inactive=500s;
          open_file_cache_valid    600s;
          open_file_cache_errors   on;
          break;
        }


        error_page 500 502 503 504 /500.html;
        keepalive_timeout 10;
}