== Introduction
Whenever is a Ruby gem that provides a clear syntax for defining cron jobs. It outputs valid cron syntax and can even write your crontab file for you. It is designed to work well with Rails applications and can be deployed with Capistrano. Whenever works fine independently as well.
Ryan Bates created a great Railscast about Whenever: http://railscasts.com/episodes/164-cron-in-ruby
Discussion: http://groups.google.com/group/whenever-gem
== Installation
$ sudo gem install whenever
== 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
More examples on the wiki: http://wiki.github.com/javan/whenever/instructions-and-examples
== Cron output
$ cd /my/rails/app
$ whenever
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
In your "config/deploy.rb" file do something like:
after "deploy:symlink", "deploy:update_crontab"
namespace :deploy do
desc "Update the crontab file"
task :update_crontab, :roles => :db do
run "cd #{release_path} && whenever --update-crontab #{application}"
end
end
This will update your crontab file, leaving any existing entries unharmed. When using the --update-crontab
option, Whenever will only update the entries in your crontab file related to the current schedule.rb file. You can replace the #{application}
with any identifying string you'd like. You can have any number of apps deploy to the same crontab file peacefully given they each use a different identifier.
If you wish to simply overwrite your crontab file each time you deploy, use the --write-crontab
option. This is ideal if you are only working with one app and every crontab entry is contained in a single schedule.rb file.
By mixing and matching the --load-file
and --user
options with your various :roles in Capistrano it is entirely possible to deploy different crontab schedules under different users to all your various servers. Get creative!
If you want to override a variable (like your environment) at the time of deployment you can do so with the --set
option: http://wiki.github.com/javan/whenever/setting-variables-on-the-fly
== Defining custom job types
You can define custom job types in your schedule file:
job_type :rails3_runner do |job|
job.command = "rails runner"
job.uses_bundler = true
end
every 1.day, :at => "2am" do
rails3_runner "MyModel.do_something_amazing"
end
This would create a job with the command "bundle exec rails runner".
By defining jobs like this, you can also make reusable system commands such as:
job_type :my_great_command do |job|
job.no_environment = true # this stops whenever appending '-e production' to the task
job.command = "/usr/bin/my_great_command"
end
every 3.days do
my_great_command "arg1 arg2 arg3"
end
== Credit
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
While building Whenever, I learned a lot by digging through the source code of Capistrano - http://github.com/jamis/capistrano
== 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
== 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.