config.yml

---
    environment: production
    chdir: /path/to/my/app
    address: 127.0.0.1
    user: root
    group: root
    port: 4567
    pid: /path/to/my/app/thin.pid
    rackup: /path/to/my/app/config.ru
    log: /path/to/my/app/thin.log
    max_conns: 1024
    timeout: 30
    max_persistent_conns: 512
    daemonize: true

gistfile1.txt

thin -s 2 -C config.yml -R config.ru start

lighttpd.conf

$HTTP["host"] =~ "(www\.)?mydomain\.com"  {
        proxy.balance = "fair"
        proxy.server =  ("/" =>
                                (
                                        ( "host" => "127.0.0.1", "port" => 4567 ),
                                        ( "host" => "127.0.0.1", "port" => 4568 )
                                )
                        )
}