MRI pipe limit (on OS X). This script fails on my Mac after creating 125 x 2 pipe endpoints, raising "Too many open files (Errno::EMFILE)" This is the cause of the problem illustrated here: https://gist.github.com/Felixyz/5788285

gistfile1.rb

wakeups = []
wakers = []

puts "Creating pipes..."

200.times do |n|
  puts "[#{n}]"
  wakeup, waker = IO.pipe
  wakeups << wakeup
  wakers << waker
end

puts "Closing pipes..."
wakeups.each {|pipe| pipe.close rescue nil}
wakers.each {|pipe| pipe.close rescue nil}

Just in case anyone stumbles upon this: the problem is the OS limit on open files, as seen by running ulimit -a
Seems the default value has been increased btw 10.8.2 and 10.8.4. In any case, raising the number of allowed file descriptors solves the problem. (http://superuser.com/questions/261023/how-to-change-default-ulimit-values-in-mac-os-x-10-6)

Interesting to note that JRuby copes even with a small ulimit -n value.