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

$ gem install whenever

Or with Bundler in your Gemfile.

gem 'whenever', :require => false

$ cd /my/rails/app
$ wheneverize .

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

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

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

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.

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"

By default, whenever runs jobs in the production environment. You can specify an environment to use in your deploy.rb file using:

set :whenever_environment, "dev"

If you are using capistrano multi-stage, and you have a rails environment for each stage, you might consider using:

set :whenever_environment do stage end

To configure jobs that should only run in one of your environments, you can add them in your schedule.rb like so:

case environment when "production" every 15.minutes do runner "Session.expire" end when "staging" every 30.minutes do runner "Session.expire" end when "qa" end

$ 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.

Whenever was created for use at Inkling (http://inklingmarkets.com) where I work. 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

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.

Copyright (c) 2009+ Javan Makhmali

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