Crono is a time-based background job scheduler daemon (just like Cron) for Ruby on Rails.
Currently, there is no such thing as Ruby Cron for Rails. Well, there's Whenever but it works on top of Unix Cron, so you can't manage it from Ruby. Crono is pure Ruby. It doesn't use Unix Cron and other platform-dependent things. So you can use it on all platforms supported by Ruby. It persists job states to your database using Active Record. You have full control of jobs performing process. It's Ruby, so you can understand and modify it to fit your needs.
Add the following line to your application's Gemfile:
gem 'crono'Run the bundle command to install it.
After you install Crono, you can run the generator:
rails generate crono:install
It will create a configuration file config/cronotab.rb and migration
Run the migration:
rake db:migrate
Now you are ready to move forward to create a job and schedule it.
- Crono v1.1.2 and older are compatible with Ruby 2.7.x and older
- Crono v2.0.0 and newer are compatible with Ruby 2.7.x and newer
You can specify a simple job by editing config/cronotab.rb:
# config/cronotab.rb
class TestJob
def perform
puts 'Test!'
end
end
Crono.perform(TestJob).every 5.secondsThen, run a crono process:
bundle exec crono -e development
Schedule list is defined in the file config/cronotab.rb, that created using rake crono:install. The semantic is pretty straightforward:
# config/cronotab.rb
Crono.perform(TestJob).every 2.days, at: {hour: 15, min: 30}
Crono.perform(TestJob).every 1.week, on: :monday, at: "15:30"You can schedule one job a few times if you want the job to be performed a few times a day or a week:
Crono.perform(TestJob).every 1.week, on: :monday
Crono.perform(TestJob).every 1.week, on: :thursdayThe at can be a Hash:
Crono.perform(TestJob).every 1.day, at: {hour: 12, min: 15}You can schedule a job with arguments, which can contain objects that can be serialized using JSON.generate
Crono.perform(TestJob, 'some', 'args').every 1.day, at: {hour: 12, min: 15}You can set some options that not passed to the job but affect how the job will be treated by Crono. For example, you can set to truncate job logs (which stored in the database) to a certain number of records:
Crono.perform(TestJob).with_options(truncate_log: 100).every 1.week, on: :mondayCrono can use Active Job jobs from app/jobs/. Here's an example of a job:
# app/jobs/test_job.rb
class TestJob < ActiveJob::Base
def perform(options)
# put you scheduled code here
# Comments.deleted.clean_up...
end
endThe ActiveJob jobs are convenient because you can use one job in both periodic and enqueued ways. But Active Job is not required. Any class can be used as a crono job if it implements a method perform:
class TestJob # This is not an Active Job job, but pretty legal Crono job.
def perform(*args)
# put you scheduled code here
# Comments.deleted.clean_up...
end
endHere's an example of a Rake Task within a job:
# config/cronotab.rb
require 'rake'
Rails.app_class.load_tasks
class Test
def perform
Rake::Task['crono:hello'].execute
end
end
Crono.perform(Test).every 5.secondsWith the rake task of:
# lib/tasks/test.rake
namespace :crono do
desc 'Update all tables'
task :hello => :environment do
puts "hello"
end
endPlease note that crono uses threads, so your code should be thread-safe
Run crono in your Rails project root directory:
bundle exec crono -e development
Usage:
Usage: crono [options] [start|stop|restart|run]
-C, --cronotab PATH Path to cronotab file (Default: config/cronotab.rb)
-L, --logfile PATH Path to writable logfile (Default: log/crono.log)
-P, --pidfile PATH Deprecated! use --piddir with --process_name; Path to pidfile (Default: )
-D, --piddir PATH Path to piddir (Default: tmp/pids)
-N, --process_name NAME Name of the process (Default: crono)
-m, --monitor Start monitor process for a deamon (Default false)
-e, --environment ENV Application environment (Default: development)
To run Crono as a daemon, please add to your Gemfile:
gem 'daemons'Then:
bundle install; bundle exec crono start RAILS_ENV=development
There are "start", "stop", and "restart" commands.
Crono can display the current state of Crono jobs.
Add the following to your config/routes.rb:
Rails.application.routes.draw do
mount Crono::Engine, at: '/crono'
...Access management and other questions described in the wiki.
For Rails 5, in case of the errors:
`require': cannot load such file -- rack/showexceptions (LoadError)
See the related issue #52
Use the capistrano-crono gem (github).
Feel free to create an issues
Please see LICENSE for licensing details.
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