Inspired by the ease of installing and setting up fitter-happier as a Rails application's health check, but frustrated by its lack of flexibility, OK Computer was born. It provides a robust endpoint to perform server health checks with a set of built-in plugins, as well as a simple interface to add your own custom checks.

For more insight into why we built this, check out our blog post introducing OK Computer.

OkComputer currently supports the following Rails versions:

• 6.1
• 6.0
• 5.2
• 5.1
• 4.2

If you use Grape instead of Rails, check out okcomputer-grape.

Add this line to your application's Gemfile:

gem 'okcomputer'

And then execute:

$ bundle

Or install it yourself as:

$ gem install okcomputer

To perform the default checks (application running and ActiveRecord database connection), do nothing other than adding to your application's Gemfile.

We also include a MongoidCheck, but do not register it. If you use Mongoid, replace the default ActiveRecord check like so:

OkComputer::Registry.register "database", OkComputer::MongoidCheck.new

If you use another database adapter, see Registering Custom Checks below to build your own database check and register it with the name "database" to replace the built-in check, or use OkComputer::Registry.deregister "database" to stop checking your database altogether.

Optionally require HTTP Basic authentication to view the results of checks in an initializer, like so:

# config/initializers/okcomputer.rb
OkComputer.require_authentication("username", "password")

To allow access to specific checks without a password, optionally specify the names of the checks:

# config/initializers/okcomputer.rb
OkComputer.require_authentication("username", "password", except: %w(default nonsecret))

By default, OkComputer routes are mounted at /okcomputer. If you'd like to use an alternate route, you can configure it with:

# config/initializers/okcomputer.rb
OkComputer.mount_at = 'health_checks'    # mounts at /health_checks

For more control of adding OkComputer to your routes, set OkComputer.mount_at = false to disable automatic mounting, and you can manually mount the engine in your routes.rb.

# config/initializers/okcomputer.rb
OkComputer.mount_at = false

# config/routes.rb, at any priority that suits you
mount OkComputer::Engine, at: "/custom_path"

Log check results by setting OkComputer.logger. Note: results will be logged at the info level.

OkComputer.logger = Rails.logger

[okcomputer] mycheck: PASSED mymessage (0s)

Register additional checks in an initializer, like so:

# config/initializers/okcomputer.rb
OkComputer::Registry.register "resque_down", OkComputer::ResqueDownCheck.new
OkComputer::Registry.register "resque_backed_up", OkComputer::ResqueBackedUpCheck.new("critical", 100)

# This check works on 2.4.0 and above versions of resque-scheduler
OkComputer::Registry.register "resque_scheduler_down", OkComputer::ResqueSchedulerCheck.new

The simplest way to register a check unique to your application is to subclass OkComputer::Check and implement your own #check method, which sets the display message with mark_message, and calls mark_failure if anything is wrong.

# config/initializers/okcomputer.rb
class MyCustomCheck < OkComputer::Check
  def check
    if rand(10).even?
      mark_message "Even is great!"
    else
      mark_failure
      mark_message "We don't like odd numbers"
    end
  end
end

OkComputer::Registry.register "check_for_odds", MyCustomCheck.new

Register an optional check like so:

# ...
OkComputer::Registry.register "some_optional_check", OkComputer::ResqueBackedUpCheck.new("critical", 100)
# ...

OkComputer.make_optional %w(some_optional_check another_optional_check)

This check will run and report its status, but will not affect the HTTP status code returned.

The plain-text output flows through Rails' internationalization framework. Adjust the output as necessary by defining okcomputer.check.passed and okcomputer.check.failed keys in your setup. The default values are available in okcomputer.en.yml.

By default, OkComputer runs checks in sequence. If you'd like to run them in parallel, you can configure it with:

# config/initializers/okcomputer.rb
OkComputer.check_in_parallel = true

• Perform a simple up check: https://example.com/okcomputer
• Perform all installed checks: https://example.com/okcomputer/all
• Perform a specific installed check: https://example.com/okcomputer/database

Checks are available as plain text (by default) or JSON by appending .json, e.g.:

• https://example.com/okcomputer.json
• https://example.com/okcomputer/all.json

If NewRelic is installed, OkComputer automatically disables NewRelic monitoring for uptime checks, as it will start to artificially bring your request time down.

If you'd like to intentionally count OkComputer requests in your NewRelic analytics, set:

# config/initializers/okcomputer.rb
OkComputer.analytics_ignore = false

$ bundle install

OkComputer tests are written with RSpec.

To run the full test suite:

$ rake spec

You may also use the environment variable RAILS_VERSION with one of the supported versions of Rails (found at the top of this file) to bundle and run the tests with a specific version of Rails.

1. Fork it
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create new Pull Request