Introduction

Whenever is a Ruby gem that provides a clear syntax for writing and deploying cron jobs.

Installation

$ gem install whenever

Or with Bundler in your Gemfile.

gem 'whenever', :require => false

Getting started

$ cd /my/rails/app
$ wheneverize .

This will create an initial "config/schedule.rb" file you.

Example schedule.rb file

every 3.hours do
  runner "MyModel.some_process"       
  rake "my:rake:task"                 
  command "/usr/bin/my_great_command"
end

every 1.day, :at => '4:30 am' do 
  runner "MyModel.task_to_run_at_four_thirty_in_the_morning"
end

every :hour do # Many shortcuts available: :hour, :day, :month, :year, :reboot
  runner "SomeModel.ladeeda"
end

every :sunday, :at => '12pm' do # Use any day of the week or :weekend, :weekday 
  runner "Task.do_something_great"
end

every '0 0 27-31 * *' do
  command "echo 'you can use raw cron sytax too'"
end

More examples on the wiki: http://wiki.github.com/javan/whenever/instructions-and-examples

Define your own job types

Whenever ships with three pre-defined job types: command, runner, and rake. You can define your own with job_type.

For example:

job_type :awesome, '/usr/local/bin/awesome :task :fun_level'

every 2.hours do
  awesome "party", :fun_level => "extreme"
end

Would run /usr/local/bin/awesome party extreme every two hours. :task is always replaced with the first argument, and any additional :whatevers are replaced with the options passed in or by variables that have been defined with set.

The default job types that ship with Whenever are defined like so:

job_type :command, ":task :output"
job_type :rake,    "cd :path && RAILS_ENV=:environment rake :task :output"
job_type :runner,  "cd :path && script/runner -e :environment ':task' :output"

If a script/rails file is detected (like in a Rails 3 app), runner will be defined to fit:

job_type :runner,  "cd :path && script/rails runner -e :environment ':task' :output"

If a :path is not set it will default to the directory in which whenever was executed. :environment will default to 'production'. :output will be replaced with your output redirection settings which you can read more about here: http://github.com/javan/whenever/wiki/Output-redirection-aka-logging-your-cron-jobs

All jobs are by default run with bash -l -c 'command...'. Among other things, this allows your cron jobs to play nice with RVM by loading the entire environment instead of cron's somewhat limited environment. Read more: http://blog.scoutapp.com/articles/2010/09/07/rvm-and-cron-in-production

You can change this by setting your own :job_template.

set :job_template, "bash -l -c ':job'"

Or set the job_template to nil to have your jobs execute normally.

set :job_template, nil

And you'll see your schedule.rb converted to cron sytax. Note: running whenever with no options does not display your current crontab file, it simply shows you the output of converting your schedule.rb file.

Capistrano integration

Use the built-in Capistrano recipe for easy crontab updates with deploys.

In your "config/deploy.rb" file:

require "whenever/capistrano"

Take a look at the recipe for options you can set. http://github.com/javan/whenever/blob/master/lib/whenever/capistrano.rb For example, if you're using bundler do this:

set :whenever_command, "bundle exec whenever"
require "whenever/capistrano"

If you are using different environments (such as staging, production), then you may want to do this:

set :whenever_environment, defer { stage }
require "whenever/capistrano"

The capistrano variable :stage should be the one holding your environment name. This will make the correct :environment available in your schedule.rb.

The whenever command

$ cd /my/rails/app
$ whenever

This will simply show you your schedule.rb file converted to cron syntax. It does not read or write your crontab file. Run whenever --help for a complete list of options.

Credit

Whenever was created for use at Inkling (http://inklingmarkets.com). Their take on it: http://blog.inklingmarkets.com/2009/02/whenever-easy-way-to-do-cron-jobs-from.html

Thanks to all the contributors who have made it even better: http://github.com/javan/whenever/contributors

Discussion / Feedback / Issues / Bugs

For general discussion and questions, please use the google group: http://groups.google.com/group/whenever-gem

If you've found a genuine bug or issue, please use the Issues section on github: http://github.com/javan/whenever/issues

Ryan Bates created a great Railscast about Whenever: http://railscasts.com/episodes/164-cron-in-ruby It's a little bit dated now, but remains a good introduction.

License

Copyright (c) 2009+ Javan Makhmali

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.