Rainbows! is an HTTP server for sleepy Rack applications. It is based
Unicorn, but designed to handle applications that expect long
request/response times and/or slow clients.
We now use IO#trysendfile in the sendfile 1.1.0 to reduce the
cost of generating backtraces for slow clients (from EAGAIN).
Nothing new for people not serving static files (but more
on the way).
Existing “sendfile” gem users must upgrade to 1.1.0
or risk being left without sendfile support at all: