Crono - Job scheduler for Rails

Crono is a time-based background job scheduler daemon (just like Cron) for Ruby on Rails.

The Purpose

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.

Requirements

Tested with latest MRI Ruby 2.5+, 2.6+, 2.7+, Rails 5.*, and Rails 6.*. Other versions are untested but might work fine.

Installation

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:

bin/rails generate crono:install

It will create a configuration file config/cronotab.rb and migration Run the migration:

bin/rails db:migrate

Now you are ready to move forward to create a job and schedule it.

Usage

Create Job

Crono can use Active Job jobs from app/jobs/. The only requirement is that the perform method should take no arguments.

Here's an example of a job:

# app/jobs/test_job.rb
class TestJob < ActiveJob::Base
  def perform
    # put you scheduled code here
    # Comments.deleted.clean_up...
  end
end

The 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
end

Here'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'].invoke
  end
end

Crono.perform(Test).every 5.seconds

With the rake task of:

# lib/tasks/test.rake
namespace :crono do
  desc 'Update all tables'
  task :hello => :environment do
    puts "hello"
  end
end

Please note that crono uses threads, so your code should be thread-safe

Job Schedule

Schedule list is defined in the file config/cronotab.rb, that created using 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: :thursday

The 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: :monday

Run

To run Crono, first add it to your project as a binstub :

In your Rails project root directory:

bundle binstubs crono

then :

bin/crono --help

crono usage:

Usage: crono [options]
    -C, --cronotab PATH              Path to cronotab file (Default: config/cronotab.rb)
    -e, --environment ENV            Application environment (Default: development)

Run as a daemon

To run Crono as a daemon, please use systemd or supervisor.

• systemd config sample
• monit config sample

Web UI

Crono comes with a Sinatra application that can display the current state of Crono jobs. Add sinatra and haml to your Gemfile

gem 'haml'
gem 'sinatra', require: nil

Add the following to your config/routes.rb:

Rails.application.routes.draw do
  mount Crono::Web, at: '/crono'
  ...
end

Access management and other questions described in the wiki.

Known issues

For Rails 5, in case of the errors:

`require': cannot load such file -- rack/showexceptions (LoadError)

See the related issue #52

Capistrano

Use the capistrano-crono gem (github).

Support

Feel free to create issues

Known Issues

• Is not compatible with the protected_attributes gem. See: #43

License

Please see LICENSE for licensing details.