How to fix error 502?

Question

Google

6 sites are stored on one server. When going by IP, it gets to a site that constantly crashes (502 nginx)
Access log (for today there are already more than 60 thousand similar requests)

163.172.178.28 - - [23/Sep/2016:08:20:29 +0300] "POST /xmlrpc.php HTTP/1.1" 502 166 "-" "Googlebot/2.1 (+ www.google.com/bot.html ) " "-"
163.172.178.28 - - [23/Sep/2016:08:20:29 +0300] "POST /xmlrpc.php HTTP/1.1" 499 0 "-" "Googlebot/2.1 (+ www.google. com/bot.html) " "-"

And the error log, also some crazy number of requests

2016/09/23 08:20:29 [error] 12847#12847: *21054884 connect() to unix:/var/run/site.sock failed (11: Resource temporarily unavailable) while connecting to upstream, client: 163.172. 178.28, server: ddxt.gov35.ru, request: "POST /xmlrpc.php HTTP/1.1", upstream: "fastcgi://unix:/var/run/site.sock:", host: "213.176.1.1"

How to solve the problem? or just remove robots.txt from indexing?

Answer 1

163.172.178.28 is not a Google address. Looks like your site is under attack.
Vulnerability overview and solutions:
https://www.digitalocean.com/community/tutorials/h...
https://habrahabr.ru/post/215543/