How to make proxying dynamic in nginx?

Question

Nginx

Hello.
The task is to dynamically proxy to different servers depending on the subdomain (which server to proxy to is decided based on the information that lies in redis (via lua)). That is, the lua script fills in the $server variable = it is equal to either 1 or 2.
Openresty server.
location /
{
set $server "";
set $redisPort "6379";
set $redisDatabase "22";
set $redisHost "localhost";
set $domain "domain.ru";
# lua script fills $server variable = it is either 1 or 2
access_by_lua_file "/home/lua-scripts/subdomain.lua";
# Here we need code that will do proxying depending on the $server parameter
}
How to make it so that if the server variable $server = 1 - do not do proxying at all (stay on this server for php processing), if 2 - do = proxy_pass http://122.22.22:6789 ?
Tried through if ($server = 2) { proxy_pass http://122.22.22:6789 } - but it doesn't work for some reason.
Thanks in advance

Answer 1

Map module to help: nginx.org/ru/docs/http/ngx_http_map_module.html

Answer 2

Tried:

proxy_pass http://127.0.0.1:6789;

if ( $server ~ 2 ) {
  proxy_pass http://122.22.22:6789;
}

Answer 3

For example, through the Lua module.
And you are already studying Lua, judging by your questions
https://habrahabr.ru/post/321864/
https://habrahabr.ru/company/2gis/blog/199504/
https://habrahabr.ru/post/215237/
https://habrahabr.ru/post/326486/