nginx config: Mysterious redirect loop when using a variable in the server_name directive. Where are the loot?

Question

Nginx

Hello. Faced with mysticism.
There is a config (one file):

server {
  server_name  www.test.ru;
  return        301 http://test.ru$request_uri;
}

server {
  set $somevar test.ru;
  listen   80;
  server_name  $somevar;
  root   /var/www/$somevar;
..и др.

When using it, there is an eternal redirect from test.ru even without www.
If you remove a piece

server {
  server_name  www.test.ru;
  return        301 http://test.ru$request_uri;
}

Or remove the variable from server_name
server_name test.ru;
Then everything will work like clockwork.
I don't understand the problem mechanism. Where are the loot?
Thanks for reading. I hope for answers. Any ideas are welcome.

Answer 1

The `server_name` directive cannot contain variables.
As a result, you have two servers, one named `www.test.ru`, the second named `$somevar`.
The request to the `test.ru` server does not find a server with the same name, gets to the default server, in this case the first one, and an endless redirect is obtained.