rails 2 and slow external services

[ghazel at gmail.com]

Hi,

Some of my page loads (currently serviced by Unicorn) spend a great
deal of time waiting for external services (OpenID, OAuth, etc over
Net::HTTP and curb), so I'm looking at Rainbows!. I use Rails 2.3.10.
Which concurrency model in Rainbows! is best suited for this sort of
page? I'm not totally clear on which parts if any of Rails are
thread-safe.

Thanks in advance!

-Greg