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README.rdoc

Cronjobs

Cronjobs is a Rails plugin that allows to schedule tasks with a cronjob-like syntax.

This plugin was inspired by the Taskit plugin.

Up to now schedules no more fine than the day is available.

Install and setup

Gem

Add this line to your Gemfile

gem 'cronjobs', :git => 'git://github.com/mperrando/cronjobs.git'

and run bundler

bundle

Database

Create the migrations and run them.

rails g schedules_migration
rake db:migrate

System cron

You need to schedule a system cronjob that runs the rake task cronjobs:run with the desired periodicity.

This rake task looks for jobs whos schedules are not yet run, schedules them and then runs the execution engine that executes alla scheduled jobs not already launched.

Add to you crontab a line that invokes the cronjobs main task. The periodicity of the cronjob must depend on the finer granularity of your scheduled tasks.

In this example, the rake task is invoked each night at 1:10 AM.

10 1 * * * cd <your_project> && RAILS_ENV=<env> rake cronjobs:run

Usage

Create you cronjob

class MyCronjob < ActiveRecord::Base
    acts_as_cronjob

    def execute
        #place your code here
    end
end

Then create one or more schedules for one of these cronjobs. First of all create one job

job = MyCronjob.new

Then create a schedule for it

sch = Cronjobs::Schedule.new(job)

You can access the schedules created for a single cronjob

job.schedules

In the case the attribute schedules must represent something else in your model, you can change the attribute name to access the schedules with the option :as

class MyCronjob < ActiveRecord::Base
    acts_as_cronjob, :as => :programs
end

and access the schedules with

job.programs

Executions

Each schedule has an execution list, each element representing an execution of that schedule.

Internal

Scheduler

The schedueler calculates, for each all the schedules, the most recent moment in which the schedule shold have run. Then it looks for the schedules whose last_scheduled_at attribute is before that moment and creates a new execution for each of them.

NOTE: if the same job has two (or more) schedules, and such schedules implies that it runs at the same moment, then the job will be launched twice (or more times).

Executor

The executor takes care of running the executions that are scheduled by the scheduler.

DirectExecutor

This is the first, simple implmentation for an executor.

The executor looks for all the executions that are not launched yet, and simply launches them, one after the other, in a single threaded style.

TODO

  • support scheduling for finer intervals, up to the minute.

  • add new Executors that allow to run the jobs on external queueing engines such as beanstalkd.