Motorhead
Motorhead is a prototyping framework for Rails. It's something akin to "feature toggle". It can be used for "A/B testing" as well. But essentially, the main purpose of this framework is to provide a way to rapidly and safely deliver new features to the production environment.
Installation
Bundle into your Rails app.
Features
Isolated Engine
Motorhead helps you mounting specially creafted Isolated Engines onto the main Rails app. An engine can contain whole MVC components, which means that you can encapsulate everything that are needed for your new feature under one single directory. This helps your team creating multiple new features simultaneously without causing code conflict.
Conditional Execution
Each Motorhead engine can be configured to be enabled/disabled. The condition is not just a flag but can be a Ruby Proc which will be dynamically evaluated on each request in the controller context.
Error-proof
If any RuntimeError happens inside an engine on the production environment, Motorhead absorbs the error and executes the appropriate fallback code so that the end users would never even notice the occurrence of the error.
Extending Action Methods in the Main App
Motorhead provides an interface to override the main app's controller actions.
Partially Extending Views in the Main App
Motorhead provides a hook to partially overwrite any part of your existing view.
Structure
main_app
├── Gemfile
├── Gemfile.lock
├── Rakefile
├── app
│ ├── assets
│ ├── controllers
│ ├── engines
│ │ ├── my_awesome_new_feature
│ │ │ ├── app
│ │ │ │ ├── assets
│ │ │ │ ├── controllers
│ │ │ │ │ └── my_awesome_new_feature
│ │ │ │ │ └── welcome_controller.rb
│ │ │ │ ├── helpers
│ │ │ │ │ └── my_awesome_new_feature
│ │ │ │ │ └── welcome_helper.rb
│ │ │ │ ├── mailers
│ │ │ │ ├── models
│ │ │ │ └── views
│ │ │ │ ├── layouts
│ │ │ │ │ └── my_awesome_new_feature
│ │ │ │ │ └── application.html.erb
│ │ │ │ └── my_awesome_new_feature
│ │ │ │ └── welcome
│ │ │ ├── config
│ │ │ │ └── routes.rb
│ │ │ ├── lib
│ │ │ │ ├── my_awesome_new_feature
│ │ │ │ │ └── engine.rb
│ │ │ │ ├── my_awesome_new_feature.rb
│ │ │ │ └── tasks
│ │ │ ├── my_awesome_new_feature.gemspec
│ │ │ └── test
│ │ └── yet_another_new_feature
│ │ ├── app
│ │ ...
│ ├── helpers
│ ├── mailers
│ ├── models
│ └── views
├── bin
├── config
├── db
...
Components
lib/ENGINE_NAME/engine.rb
Put active_if
directive inside the Engine class. The whole engine will only be executed if the block is evaluated to be truthy on runtime.
Example:
# app/engines/my_awesome_new_feature/config/routes.rb
module MyAwesomeNewFeature
class Engine < ::Rails::Engine
include Motorhead::Engine
# this whole engine will be executed only when logged in as admin users
active_if { current_user.admin? }
end
end
You can configure a path to mount the Engine via mount_at
directive. This value is defaulted to "/", which means the Engine routes will be mixed into the main app's routes.
Example:
# app/engines/my_awesome_new_feature/config/routes.rb
module MyAwesomeNewFeature
class Engine < ::Rails::Engine
include Motorhead::Engine
# all routes inside this Engine will be prefixed by "/harley"
mount_at 'harley'
end
end
routes.rb
All routes in engines' routes.rb will be automatically prepended to the main app's Routes.
Controllers
Controllers can be a normal Engine controller.
Or, you can craft a controller class inheriting a controller that exists in the main app, and overriding some action methods.
From inside the actions in engines, you can call the main app's action via super
.
Example:
# app/engines/my_awesome_new_feature/app/controllers/my_awesome_new_feature/welcome_controller.rb
class MyAwesomeNewFeature::WelcomeController < ::WelcomeController
include Motorhead::Controller
def index
# invoking the main app's action first
super
# adding some more business logic
@notifications = Notification.for current_user
end
end
Views
When an engine renders the views, it looks up app/views/ENGINE_NAME/ directory first, then the main app's view directory next. This way you can overwrite views per template/partial file.
Also, Motorhead adds new :engine
option to render
method, which enables you to explicitly inject a piece of HTML from an engine into any place of the app.
render :engine
takes an `ENGINE_NAME/view_path' parameter.
Example:
# app/engines/my_awesome_new_feature/app/views/my_awesome_new_feature/welcome/_index.html.haml
.new_feature
Some contents for new feature
# app/views/welcome/index.html.haml
= render engine: 'my_awesome_new_feature/welcome/index' do
Some contents that will be shown by default
Generators
Motorhead provides some handy code generators.
Generating an engine
% rails g motorhead ENGINE_NAME
Example:
% rails g motorhead my_awesome_new_feature
This generates a motorhead Engine in ~/app/engines/my_awesome_new_feature/ directory.
Generating an engine + a controller extension that extends an existing controller
% rails g motorhead ENGINE_NAME CONTROLLER_NAME [action action] [options]
Example:
% rails g motorhead my_awesome_new_feature welcome index
This generates a motorhead Engine in ~/app/engines/my_awesome_new_feature/ directory. Plus, a controller that extends WelcomeController and implements index action inside the Engine.
Managing Engines
Motorhead includes a tiny admin console Engine call "RoadCrew" through which you can easily enable/disable each mounted Engine.
To use this, require 'motorhead/road_crew'
when bundling motorhead gem in your Gemfile:
# Gemfile
gem 'motorhead', path: '~/src/motorhead', require: ['motorhead', 'motorhead/road_crew']
then render the road_crew/button
Engine partial to put a button inside somewhere in your view (usually in the header or footer?):
# app/views/layouts/application.html.erb
<%= render engine: 'road_crew/button' %>
You might also want to configure the RoadCrew Engine's active_if
directive for security.
# config/initializers/mh_road_crew.rb
RoadCrew::Engine.active_if { current_user.admin? }
Contributing
Pull requests are welcome on GitHub at https://github.com/amatsuda/motorhead.
Todo
-
Better generator
-
Model extension
-
Documentation
Special Thanks
This product is deeply inspired by Chanko.
License
The gem is available as open source under the terms of the MIT License.