resolv_timeout.rb

require 'net/http'
require 'socket'
def with_unresponsive_dns
  fake_dns_ip = "127.0.0.1"
  th = Thread.new do
    server = UDPSocket.new
    server.bind(fake_dns_ip, 53)
    server.recvfrom(16)
    sleep
  end

  original_dns = %x(cat /etc/resolv.conf |grep -i '^nameserver'|head -n1|cut -d ' ' -f2).strip
  `echo "$(sed 's/#{original_dns}/#{fake_dns_ip}/g' /etc/resolv.conf)" > /etc/resolv.conf`
  yield
ensure
  `echo "$(sed 's/#{fake_dns_ip}/#{original_dns}/g' /etc/resolv.conf)" > /etc/resolv.conf`
  th.kill
  th.join
end

now = Time.now
begin
  with_unresponsive_dns do
    uri = URI('http://example.com/some_path?query=string')
    puts "beginning HTTP request. This should timeout after 1s"
    Net::HTTP.start(uri.host, uri.port, open_timeout: 1)
  end
ensure
  puts "elapsed: #{Time.now - now}"
end