class Bundler::Persistent::Net::HTTP::Persistent::Pool

def checkout net_http_args
  stacks = Thread.current[@key] ||= {}
  stack  = stacks[net_http_args] ||= []
  if stack.empty? then
    conn = @available.pop connection_args: net_http_args
  else
    conn = stack.last
  end
  stack.push conn
  conn
end