CheckerJobs

This gems provides a small DSL to check your data for inconsistencies.

Introduction

To ensure database integrity, DBMS provides some tools: foreign keys, triggers, strored procedures, ... Those tools aren't the easiests to maintain unless your project is based on them. Also, you may want to avoid to duplicate your business rules from your application to another language and add operational complexity around deployment.

This gem doesn't aim to replace those tools but provides something else that could serve a close purpose: ensure that you work with the data you expect.

This gem helps you schedule some verifications on your data and get alerts when something is unexpected. You declare checks that could contain any business code you like and then those checks are run by your application, in background jobs.

A small DSL is provided to helps you express your predicates:

• ensure_no will check that the result of a given block is zero?, empty? or false
• ensure_more will check that the result of a given block is >= than a given number
• ensure_fewer will check that the result of a given block is <= than a given number

and an easy way to configure notifications.

For instance, at Drivy we don't expect users to get a negative credit amount. It isn't easy to get all the validation right because many rules are in play here. Because of those rules the credit isn't just a column in our database yet but needs to be computed based on various parameters. What we would like to ensure is that no one ends up with a negative credit. We could write something like:

class UsersChecker
  include CheckerJobs::Base

  options sidekiq: { queue: :slow }

  notify :email, to: "[email protected]"

  ensure_no :negative_rental_credit do
    # The following code is an over-simplification
    # Real code is more performance oriented...

    user_ids_with_negative_rental_credit = []

    User.find_each do |user|
      if user.credit_amount < 0
        user_ids_with_negative_rental_credit << user.id
      end
    end

    user_ids_with_negative_rental_credit
  end
end

Then when something's wrong, you'll get alerted.

You'll find more use cases and tips in the wiki.

Installation

Add this line to your application's Gemfile:

gem 'checker_jobs'

Usage

Have a look at the examples directory of the repository to get a clearer idea about how to use and the gem is offering.

Configure

require "checker_jobs"

CheckerJobs.configure do |c|
  c.jobs_processor = :sidekiq

  c.notifier :bugsnag do |options|
    options[:formatter_class] = CheckerJobs::Notifiers::BugsnagDefaultFormatter
  end

  c.notifier :email do |options|
    options[:formatter_class] = CheckerJobs::Notifiers::EmailDefaultFormatter
    options[:email_options] = {
      from: "[email protected]",
      reply_to: "[email protected]",
    }
  end

  c.notifier :logger do |options|
    options[:logdev] = STDOUT
    options[:level] = Logger::INFO
  end

  c.repository_url = { github: "drivy/checker_jobs" }
end

This piece of code usually goes into the config/initializers/checker_jobs.rb file in a rails application. It relies on the fact that ActionMailer and sidekiq are already configured.

If you're on a different stack and you'll like to add a new job processor or notification backend in this gem, drop us a line.

Job Processor

At the moment, only Sidekiq is supported as a job processor to asynchronously check for data inconsitencies. The gem is designed to supports more processor. PRs are appreciated 🙏

Notifiers

We support different kind of notifiers, as of today we have the following:

• :bugsnag: uses Bugsnag to send notifications. It takes the global Bugsnag configuration.
• :email: uses ActionMailer to send emails. You can pass it any ActionMailer options.
• :logger: Uses Logger to output inconsitencies in the log. Takes the following params:
  • logdev: The log device. This is a filename (String) or IO object (typically STDOUT, STDERR, or an open file).
  • level: Logging severity threshold (e.g. Logger::INFO)

Write checkers

A checker is a class that inherits CheckerJobs::Base and uses the DSL to declare checks.

class UserChecker
  include CheckerJobs::Base

  options sidekiq: { queue: :fast }

  notify :email, to: "[email protected]"

  ensure_no :user_without_email do
    UserRepository.missing_email.size
  end
end

The UserChecker will have the same interface as your usual jobs. In this example, UserChecker will be a Sidekiq::Worker. Its #perform method will run the check named :user_without_email and if UserRepository.missing_email.size is greater than 0 then an email will be fired through ActionMailer to [email protected].

Schedule checks

Once you have checker jobs, you'll need to run them. There are many task schedulers out there and it isn't really relevant what you'll be using.

You have to enqueue your job as often as you like and that's it.

UserChecker.perform_async

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/drivy/checker_jobs.

You'll find out that the CI is setup to run test coverage and linting.

License

The gem is available as open source under the terms of the MIT License.