I use ngix as reverse proxy. Is there a way to show a specifc html page, if the port (e.g. 1111) is not available (e.g. during restart of the application):

location /app/ {
    proxy_pass http://127.0.0.1:1111/;
    proxy_set_header X-Real-IP $remote_addr;
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
}