Ngnix conf that contains /check url that can go dark if file exists

nginx.conf

user www-data;
worker_processes 4;
pid /var/run/nginx.pid;



events {
  worker_connections 1024;
  use epoll;
  multi_accept on;
}


http {

  include /etc/nginx/mime.types;
  index    index.html index.htm;

  default_type application/octet-stream;

  sendfile     on;
  tcp_nopush   on;
  tcp_nodelay on;
  server_names_hash_bucket_size 128;
  keepalive_timeout    70;
  types_hash_max_size 2048;


  gzip on;
  gzip_disable "msie6";

  log_format  main_fmt '$remote_addr - $remote_user [$time_local]  $status '
    '"$request" $body_bytes_sent "$http_referer" '
    '"$http_user_agent" "$http_x_forwarded_for"';


  proxy_buffering    off;
  proxy_set_header   X-Real-IP $remote_addr;
  proxy_set_header   X-Scheme $scheme;
  proxy_set_header   X-Forwarded-For $proxy_add_x_forwarded_for;
  proxy_set_header   Host $http_host;

  access_log /var/log/nginx/access.log main_fmt;

  server {
      listen       8080;
      server_name  localhost;

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

      location /check {
        if (-f /tmp/check) {
           return  404;
        }
         add_header Content-Type text/plain;
         return 200 "UP";
      }


      error_page   500 502 503 504  /50x.html;
      location = /50x.html {
          root   /usr/share/nginx/html;
      }
  }

}