444 return code and rate limiting

[c0nw0nk]

What I would say to do is write IP's from your toolkit or what ever you are
using for reading your access.log and those that trigger and spam the 503
error within milliseconds or what ever range it is you can do an API call
and add those IP's to be blocked at a router level.

With CloudFlare you can have CloudFlare block those IP's before they reach
your server like so
https://api.cloudflare.com/#user-level-firewall-access-rule-properties

If you use OVH you can write the IP's that trigger 503's to OVH's Firewall
https://api.ovh.com/console/#/ip/{ip}/firewall#POST

This should be of interest too
https://twitter.com/olesovhcom/status/779297257199964160

But anything the firewall does not get your server now has a way to
communicate with your router / firewall to prevent this requests even
hitting the machine any more.

Posted at Nginx Forum: https://forum.nginx.org/read.php?2,269873,269881#msg-269881