sync.rb

require 'celluloid'
require 'active_job'

class MasterQueue
  include Celluloid

  attr_accessor :jobs, :current_job

  def initialize
    @jobs = Queue.new
    @current_job = nil

    @timer = every(1) {
      if !@jobs.empty? && (@current_job.nil? || @current_job.complete)
        @current_job = @jobs.pop
        @current_job.perform
      end

      puts "fired timer. jobs: #{@jobs.size}"
    }
  end

  def push_job(job)
    @jobs << job
  end
end

class MyJob < ActiveJob::Base
  attr_accessor :name
  attr_accessor :complete

  def initialize(name)
    @name = name
  end

  def perform
    sleep( rand(1) )
    puts "performing: #{@name}"
    @complete = true
  end
end

queue = MasterQueue.new
10.times { |i|
  queue.push_job( MyJob.new(i) )
}

while(true)
  sleep(5)
end