Disibuted CRON?!

dcron.rb

# Job, Desc, Interval, Tick, updated_at

class Job
  attr_reader :name
  attr_accessor :task, :working

  def initialize(name, interval, offset)
    @name = name
    @interval = interval
    @offset = offset
    @executed_at = 0
    @alive = false
  end

  def check(at = Time.now)
    frame = (at.to_i % @interval) - @offset
    # check how often the interval was checked, what if
    # the job finished in a time longer than the interval?
    if (frame >= 0) && (frame < @interval * 0.20) &&
       (at.to_i - @executed_at) >= @interval
      if @alive
        @working.call(at.to_i - @executed_at) if @working
        @alive = false if @alive && rand > 0.7
      else
        @task.call(at.to_i - @executed_at) if @task
        @executed_at = at.to_i
        @alive = true
      end
    end
  end
end

# UPDATE jobs SET updated_t = Time.now, tick = tick + 1, worker = 1
# WHERE Time.now - updated_at >= 1 AND id = X

# SELECT worker, active FROM jobs WHERE id = X

jobs = [
  Job.new("Clean dishes every 5s", 5, 0),
  Job.new("Clean kitchen", 
          24 * 60 * 60,
           8 * 60 * 60 - 2 * 60 * 60 + # 2h (GMT + Summertime)
               23 * 60)
]

jobs.each_with_index do |job, i|
  job.task = lambda { |after|
    puts "execute #{job.name.inspect} by #{i + 1}. thread after #{after}"
  }

  job.working = lambda { |since|
    puts "still processing since #{since}"
  }
end

workers = []
5.times do |i|
  workers << Thread.new do
    sleep i * rand

    loop do
      jobs.each do |job|
        job.check
      end

      sleep 5 * rand
    end
  end
end

workers.each(&:join)