request rate limiting + whitelist Google

Hello guys, Am wondering if once can rate-limit (reqs/second or /minute) globally, but also whitelist Google (and other crawlers), by hardcoding their reverse dns hosts in the config? If reverse dns/host check is no-go, can the same be achieved using user agent filter? Any ideas are greatly

host specific error messages

Hello guys, Is it possible to set host specific error files in the config? That is to server /etc/error/503.html for www.this.com but /etc/error/503_alter.html for www.that.com ? If so how? :) Both hosts are served by the same listen directive atm. Was looking at acls and hdr_beg(host) -i,