Using environment vars in lighttpd config files

Our game is hosted on a farm of servers behind a load balancer. All servers are identical except for their names (prod-01, prod-02, etc) and virtual IP addresses.

In PHP, if I try to access $_SERVER['SERVER_NAME'], I only got the domain name "prod.game.com". Actually, this was exactly the same var as the $_SERVER['HTTP_HOST'].

For logging purposes, I needed to know the name of the server that my script was currently running on. So I updated my lighttpd.conf

Lighty has a feature called include_shell that you can use in its config files. It will basically run a shell script and add its output to your file.

So I wrote a simple shell script to define a var.serverName (this is a custom value, name it as you want, but keep the var prefix) and then re-use when needed.

#!/bin/bash
echo 'var.serverName="'$(uname -n)'"'

Then, I included it in my lighttpd.conf file using include_shell "/etc/lighttpd/scripts/serverName.sh"

To define the PHP SERVER_NAME value:

setenv.add-environment = (
  "SERVER_NAME" => var.serverName
)

To add it as a Server: response Header:

server.tag = var.serverName

Note that include_shell directives are only called when you start lighty and not on every request.