worker_respawner.rb

class Worker
  attr_reader :id

  def initialize(id)
    @id = id
    puts "Spawned new worker with id: #{id}"
  end

  def dead?
    return true if @killed

    result = (rand(6) == 0)
    puts "#{id} died" if result

    result
  end

  def kill
    puts "#{id} killed"
    @killed = true
  end

  def ==(other_val)
    return (id == other_val) if other_val.is_a?(Fixnum)
    super
  end
end

pool = {}
target_number = 5

while true
  pool.reject! { |k, v| v.dead? } # Clean out dead workers
  pool.each { |k, v| v.id >= target_number && v.kill }

  if pool.size < target_number
    target_number.times do |n|
      next if pool.value?(n)
      puts "Failed" if pool[n]
      pool[n] = Worker.new(n)
    end
  end

  puts "Active: #{pool.keys.inspect}"

  # Adjust how many workers we're rocking
  target_number += (rand(3) - 1)
  target_number = 0 if target_number < 0

  sleep 0.5
end