eventmachine-fork-example.rb

require 'rubygems'
require 'eventmachine'

children = []

Signal.trap('SIGINT') do
  EventMachine.next_tick { EventMachine.stop_event_loop }
end

Signal.trap('EXIT') do
  puts "Killing #{children.size} children ..."

  children.each do |pid|
    Process.kill('SIGUSR1', pid) rescue Exception
  end
end

module Connection
  def receive_data(data)
    puts "\t#{data}"
  end
end

pipe = IO.pipe

EventMachine.run do
  puts "Father PID: #{Process.pid}"

  read = EventMachine.attach(pipe[0], Connection)

  EventMachine.add_periodic_timer(1) do
    puts "Father(#{Process.pid}): #{Time.now.to_s}"
  end

  4.times do |i|
    pid = EventMachine.fork_reactor do
      read.close_connection

      write = EventMachine.attach(pipe[1])

      Signal.trap('SIGUSR1') { EventMachine.stop_event_loop }
      Signal.trap('SIGCHLD') {}
      Signal.trap('EXIT')    {}

      EventMachine.add_periodic_timer(5) do
        write.send_data "Child[#{i}](#{Process.pid}): #{Time.now.to_s}"
      end
    end

    children << pid

    puts "Child[#{i}] PID: #{pid}"

    Process.detach(pid)
  end
end

On SIGINT after "stop_event_loop" you should do

children.each do |pid|
Process.kill('SIGUSR1', pid) rescue Exception
end

as in "EXIT". In other case you will see child processes in ps aux after parent gone. Hate zombie.