[ Run cron jobs on rails (deployed over several servers) ]
What is the best way to run cron jobs on rails, when different machines have different jobs to do?
For example, server 1 runs cron job A, while server 2 runs cron job B
Is there a way to deploy the cron files along when we do a regular cap deploy?
Answer 1
take a look at the whenever gem, http://github.com/javan/whenever
It is great for automating cron tasks with rails with a clear DSL. We have been using it production for several months now and it just works and is very lightweight. Some examples from their README:
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
The README is very thorough, but there is also a good screencast on railscasts: http://railscasts.com/episodes/164-cron-in-ruby
It easily integrates with capistrano with the following code (copied from README):
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
As far as machine specific, you could use a local config file or even symlink the config/schedule.rb
file on deploy. I think I would include a local file that would be symlinked on deploy local_schedule.rb
and then put this at the top of the config/schedule.rb
if File.exists?(File.dirname(__FILE__) + '/config/local_schedule.rb')
require File.dirname(__FILE__) + '/local_schedule.rb'
end
Your schedule would run but then include anything local, just make sure it is symlinked before the cap task above is run and you should be good to go.
I hope this helps!