Anyway Config

Rails/Ruby plugin/application configuration tool which allows you to load parameters from different sources: YAML, Rails secrets, environment.

Allows you to easily follow the twelve-factor application principles and adds zero complexity to your development process.

Libraries using Anyway Config:

• Influxer

• AnyCable

• Sniffer

• and others.

Installation

1. Adding to a gem:

# my-cool-gem.gemspec
Gem::Specification.new do |spec|
  ...
  spec.add_dependency "anyway_config", "~> 1.0"
  ...
end

2. Adding to your project:

# Gemfile
gem "anyway_config", "~> 1.0"

3. Install globally:

$ gem install anyway_config

Usage

Pre-defined configuration

Create configuration class:

require 'anyway'

module MyCoolGem
  class Config < Anyway::Config
    attr_config user: 'root', password: 'root', host: 'localhost'
  end
end

attr_config creates accessors and default values. If you don't need default values just write:

attr_config :user, :password, host: 'localhost'

Then create an instance of the config class and use it:

module MyCoolGem
  def self.config
    @config ||= Config.new
  end
end

MyCoolGem.config.user #=> 'root'

Customize name

By default, Anyway Config uses the namespace (the outer module name) as the config name, but you can set it manually:

module MyCoolGem
  class Config < Anyway::Config
    config_name :cool
    attr_config user: 'root', password: 'root', host: 'localhost', options: {}
  end
end

Customize env variable names prefix

By default, Anyway Config uses underscored config name as a prefix for env variable names (e.g. config_name :my_app will result to parsing MY_APP_HOST variable). You can set env prefix explicitly, and it will be used as is:

module MyCoolGem
  class Config < Anyway::Config
    env_prefix :really_cool # now variables, starting wih `REALLY_COOL_`, will be parsed
    attr_config user: 'root', password: 'root', host: 'localhost', options: {}
  end
end

Provide explicit values

Sometimes it's useful to set some parameters explicitly during config initialization. You can do that using overrides option:

config = MyCoolGem::Config.new(
  overrides: {
    user: 'john',
    password: 'rubyisnotdead'
  }
)

# The value would not be overriden from other sources (such as YML file, env)
config.user == 'john'

Dynamic configuration

You can also create configuration objects without pre-defined schema (just like Rails.application.config_for but more powerful):

# load data from config/my_app.yml, secrets.my_app (if using Rails), ENV["MYAPP_*"]
config = Anyway::Config.for(:my_app)

Using with Rails

Your config will be filled up with values from the following sources (ordered by priority from low to high):

• RAILS_ROOT/config/my_cool_gem.yml (for the current RAILS_ENV, supports ERB). You can override this setting through special environment variable – 'MY_COOL_GEM_CONF' – containing the path to the YAML file.

• Rails.application.secrets.my_cool_gem

• ENV['MY_COOL_GEM_*'].

Using with Ruby

By default, Anyway Config is looking for a config YAML at ./config/<config-name>.yml e.g. ./config/my_cool_gem.yml. You can override this location the same way as for Rails.

Environmental variables work the same way too.

Config clear and reload

There are #clear and #reload functions on your config (which do exactly what they state).

Note: #reload also accepts overrides key to provide explicit values (see above).

OptionParser integration

It's possible to use config as option parser (e.g. for CLI apps/libraries). It uses optparse under the hood.

Example usage:

class MyConfig < Anyway::Config
  attr_config :host, :log_level, :concurrency, :debug, server_args: {}

  # specify which options shouldn't be handled by option parser
  ignore_options :server_args

  # provide description for options
  describe_options(
    concurrency: "number of threads to use"
  )

  # mark some options as flag
  flag_options :debug

  # extend an option parser object (i.e. add banner or version/help handlers)
  extend_options do |parser, config|
    parser.banner = "mycli [options]"

    parser.on("--server-args VALUE") do |value|
      config.server_args = JSON.parse(value)
    end

    parser.on_tail "-h", "--help" do
      puts parser
    end
  end
end

config = MyConfig.new

config.parse_options!(%w(--host localhost --port 3333 --log-level debug))

config.host # => "localhost"
config.port # => 3333
config.log_level # => "debug"

# Get the instance of OptionParser
config.option_parser

Rails.application.config_for vs Anyway::Config.for

Rails 4.2 introduced new feature: Rails.application.config_for. It looks very similar to Anyway::Config.for, but there are some differences:

Feature	Rails	Anyway Config
load data from config/app.yml	yes	yes
load data from secrets	no	yes
load data from environment	no	yes
return Hash with indifferent access	no	yes
support ERB within config/app.yml	yes	yes*
raise errors if file doesn't exist	yes	no

_{^*make sure that ERB is loaded}

But the main advantage of Anyway::Config is that it can be used without Rails!)

How to set env vars

Environmental variables for your config should start with your config name, uppercased and underscore-free.

For example, if your module is called "MyCoolGem" then the env var "MYCOOLGEM_PASSWORD" is used as config.password.

Environment variables are type-casted (case-insensitive).

Examples:

• "True", "t" and "yes" to true;

• "False", "f" and "no" to false;

• "nil" and "null" to nil (do you really need it?);

• "123" to 123 and "3.14" to 3.14.

Anyway Config supports nested (hashed) env variables. Just separate keys with double-underscore. For example, "MYCOOLGEM_OPTIONS__VERBOSE" is parsed as config.options["verbose"].

Array values are also supported:

# Suppose ENV["MYCOOLGEM_IDS"] = '1,2,3'
config.ids #=> [1,2,3]

If you want to provide a text-like env variable which contains commas then wrap it into quotes:

MYCOOLGEM="Nif-Nif, Naf-Naf and Nouf-Nouf"

Contributing

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 a new Pull Request