How to use connection pool in Rails2.3.5 with WEBrick and MySQL?

We use Rails 2.3.5, MySQL, and WEBrick.

ActiveRecord call ConnectionPool#checkout and create new connection to
MySQL when receive a first HTTP request.
At this time, register to connection pool its connection in

but, Rack::Handler::WEBrick#service call body.close in ensure section
when return the HTTP response.
It call another method. after some call, it call
ConnectionPool#clear_reloadable_connections and clear its connection

As a result, the connection was created by every request and spend
time for connection.

How to use connection pool?