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
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
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"
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.
If your production environment uses RVM (Ruby Version Manager) you will run into a gotcha that causes your cron jobs to hang. This is not directly related to Whenever, and can be tricky to debug. Your .rvmrc files must be trusted or else the cron jobs will hang waiting for the file to be trusted. A solution is to disable the prompt by adding this line to your user rvm file in ~/.rvmrc
rvm_trust_rvmrcs_flag=1
This tells rvm to trust all rvmrc files, which is documented here: http://wayneeseguin.beginrescueend.com/2010/08/22/ruby-environment-version-manager-rvm-1-0-0/
$ 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). 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
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.
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