This expression executes its children expression according to a cron schedule or at a given frequency.

  cron '15 4 * * sun' do # every sunday at 0415
    subprocess :ref => 'refill_the_acid_baths'
  end

or

  every '10m' do
    send_reminder # subprocess or participant
  end

The ‘tab’ or ‘interval’ attributes may be used, this is a bit more verbose, but, for instance, in XML, it is quite necessary :

  <cron tab="15 4 * * sun">
    <subprocess ref="refill_the_acid_baths" />
  <cron>

Triggered children subprocesses are ‘forgotten’. This implies they will never reply to the cron/every expression and they won‘t get cancelled when the cron/every expression gets cancelled (the cron/every schedule gets cancelled though, no new children will get cancelled).

"man 5 crontab" in the command line of your favourite unix system might help you with the semantics of the string expected by the cron expression.

an example use case

The cron/every expression appears often in scenarii like :

  concurrence :count => 1 do

    participant 'operator'

    cron '0 9 * * 1-5' do # send a reminder every weekday at 0900
      notify 'operator'
    end
  end

With a subprocess, this could become a bit more reusable :

  Ruote.process_defintion :name => 'sample' do

    sequence do
      with_reminder :participant => 'operator1'
      with_reminder :participant => 'operator2'
    end

    define 'with_reminder' do
      concurrence :count => 1 do
        participant '${v:participant}'
        cron '0 9 * * 1-5' do # send a reminder every weekday at 0900
          notify '${v:participant}'
        end
      end
    end
  end