DiceBag is a library of rake tasks for configuring web apps in the style of The Twelve-Factor App. Configuration values are picked up from the environment and used to populate configuration files from templates. Pre-packaged templates for common configuration files are provided.

Add the following to your Gemfile:

gem 'dice_bag'

If you are using these tasks outside of a Rails project, add the following to your Rakefile or wherever your local rake tasks are defined:

require 'dice_bag/tasks'

Run the following command to see the new tasks:

[bundle exec] rake -D config

When the rake "config" task is run, configuration files are populated for all ERB template files in the project that have a ".dice" extension. Configuration values from the environment are made available to the templates through the configured object.

For example, take a "database.yml.dice" file containing this template:

development:
  database: development
  username: <%= configured.database_username || 'root' %>
  password: <%= configured.database_password %>

Then run the following command:

[bundle exec] rake DATABASE_USERNAME=alice DATABASE_PASSWORD=xyzzy config

The following "database.yml" file is generated:

development:
  database: development
  username: alice
  password: xyzzy

See the feature documentation for further examples and functionality.

As discussed in The Twelve-Factor App section on configuration, do not commit your generated configuration files to source control. Instead, commit the templates to source control and then regenerate the configuration files at deployment time by running the rake config:deploy task.

Pre-packaged templates for the following configuration files in the config directory are provided:

• database.yml for Rails
• newrelic.yml for NewRelic

Run the following command to generate them:

[bundle exec] rake config:generate_all

As with your own templates, you should commit these pre-packaged templates to source control.

You can customize these pre-packaged template to your needs but if the change is a generic fix or extension, please consider contributing it back to this project so that everyone benefits.

If you want DiceBag to generate your own pre-packaged templates when you run the rake "config:generate_all" task, you can create a plug-in. Read the templates.md file to learn how to do this.

• Andrew Smith
• Jordi Carres
• Dan Hoizner
• Aaron Weiner
• Luke Greene
• Johnny Lo