Rails: How to split write/read query across master/slave databases

My website has a very heavy read traffic than write traffic.To improve
the
performance of my website i have decided to go with master/slave
database
configuration.

while searching on the internet about master/slave configuration for
rails
i came across the octopusgem. This gem is very nice and provide the
great
interface for distributing query across different master and slave
servers.

But the issue is that my rails application is very big and if i use
octopus gem
then i can’t go though a millions of source code line to change the
query
distribution(sending read query to slave server and write query to
master
server) across master and slave servers.MySQL Proxy seems to be a great
way
to resolve this issue but since it is in alpha version i don’t want to
use
it.

So my question is what is the best way to split read/write query across
master/slave server?? is it possible to split read/write query without
using any gems in rails??

Thanks,