Konfig

Konfig is a Kubernetes friendly Rails configuration file. While Rails applications can easily read YAML files to load configurations, Kubernetes is good at serving individual configuration values as files via Kubernetes Secrets. This means your Rails application needs to read the same configuration file from a YAML file in development or an individual file while running in Kubernetes. Konfig can load configuration and secrets from both YAML or folders with individual files and present them to your application the same way.

Add this line to your application's Gemfile:

gem 'rb-konfig'

And then execute:

$ bundle

Or install it yourself as:

$ gem install rb-konfig

Konfig.configuration.mode = :yaml
Konfig.configuration.workdir = "settings/folder"
Konfig.load

or if you'd like to use it in Kubernetes:

Konfig.configuration.mode = :directory
Konfig.configuration.workdir = "settings/folder"
Konfig.load

Now you can use Konfig anywhere in the code:

puts Settings.some.configuration.value

In file mode, Konfig, looks for any of the files specified in default_config_files. By default and in a non-Rails environment this will be development.yml and development.local.yml files in work_dir. In a Rails environment, this will be ENVIRONMENT.yml and ENVIRONMENT.local.yml files (ie production.yml and production.local.yml) files. Files added to the list later will override the values in the earlier defined files. This means, production.local.yml values will override production.yml values. In kubernetes mode, it looks for a file for each one of the given configuration keys. For example:

# development.yml
some:
    configuration:
        value: true

# directory mode
$ ls config/settings
-rw-r--r--    1 khash  staff    20 10 May 07:20 some.configuration.value

$ cat config/settings/some.configuration.value
true

The value in some.configuration.value file can be true. Konfig tries to clean the file and coerce the value into the right type before returning. If the file or the key in yaml is missing, it will return a Konfig::MissingConfiguration is thrown.

By default YAML returns nil for a null value in a YAML file. This is also replicated in directory mode.

Settings can be overridden by values in environment variables. To override a value, set an environment variable that reflects the full path to the setting, replacing . with _ and prefixing it with KONFIG_. You can change the prefix using Konfig.configuration.env_prefix. For example, Settings.this.is.a.test can be overridden with KONFIG_THIS_IS_A_TEST. Environment variables are not parsed for Ruby (ERB) but are coerced into the right type just like other settings.

You can change or reach the following from Konfig.configuration

• namespace: Default is Settings
• delimiter: Default is .
• default_config_files: Default is [development.yml, development.local.yml]
• allow_nil: Default is true
• nil_word: Default is null
• mode: No default value
• workdir: No default value
• schema: Configuration validation schema. If available, the loaded, merged and parsed configuration is validated against this schema. See Dry-Schema for more information.
• fail_on_validation: Fail if schema validation fails

The directory mode, supports the following data types in files and tries to return the right type:

• Integer
• Float
• String
• Boolean
• JSON
• Null (see above)

YAML mode supports ERB in your YAML file, just like default Rails behavior

After checking out the repo, run bin/setup to install dependencies. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Konfig has a CLI to generate validation schema based on a given yaml file. To generate, run:

$ konfig gs --in sample.yml

This will generate the ruby code that can be used for Konfig.configuration.schema like the one below:

Konfig.configuration.schema do
  required(:some).schema do
    required(:setting).filled(:string)
    required(:another).filled(:integer)
    required(:and_more).filled(:bool)
  end
end

Bug reports and pull requests are welcome on GitHub at https://github.com/cloud66-oss/konfig.