How to implement a non-block online RSS portal?

To implement an online rss reader just like is not
difficult.Every registered user will add their feeds to their customed
online rss reader.However,if any user have sent their request of reading
rss to the server,the server will not return until the content of the
feed is fetched and then return back.During this process,the ruby
process is blocked until the feeds is fetched, if lots of users want to
do that,will it cause a block? Since each fcgi or mongrel instance means
one ruby process and ruby does not provide a local thread.

I would use BackgroundRB to load the feeds, parse them, and place
them in a database. The client
can then poll periodically for the update.