Config Logic

Config Logic is a configuration management tool for Ruby/Rails applications. It wraps any set of config files in a managed access layer which supports

caching
multi argument, hash style, or dot style access
ordered overlays
dynamic or static multiplexing

Requirements

The following gems will be installed along with config_logic

activesupport (2.2.2+)
buffered_logger (0.1.2+)

Installation

gem install config_logic

Usage

Imagine that your application has a config directory with the following layout,

config/config_prod.yml -->

    :key1: 1 
    :key2: 2
    :key3: 3

config/config_dev.yml -->

    :key1: 11 
    :key2: 12 
    :key3: 13

config/dir1/config_prod.yml -->

    :key1: 11 
    :key2: 12 
    :key3: 13

config/dir1/config_dev.yml -->

    :key4: 1
    :key5: 2
    :key6: 3

Initialization

c = ConfigLogic.new('path/to/config/dir')
c = ConfigLogic.new(['path1', 'path2'])

Data Access

c.config.key1        => 1
c[:config][:key1]    => 1
c['config']['key1']  => 1
c(:config, :key1)    => 1
c('config', 'key1')  => 1
c.unknown            => nil
c.config.unknown     => nil

Rebuilding the Config Cache

c.reload!

Applying Overlays

An Overlay allows multiple config values to be merged in a specified order. The merge order is determined by the order of the key names in the :inputs parameter.

Global

c = ConfigLogic.new('path/to/config/dir', :overlays => [ { :name => 'config',
                                                           :inputs => [:config_prod, :config_dev] } ] )
c.config.key1 => 11
c.config.key2 => 12
c.config.key3 => 13
c.config.dir1.key1 => 11
c.config.dir1.key2 => 12
c.config.dir1.key3 => 13
c.config.dir1.key4 => 1
c.config.dir1.key5 => 2
c.config.dir1.key6 => 3

Local

c.config.insert_overlay( { :name => 'config',
                           :inputs => [:config_prod, :config_dev] } )
c.config.key1 => 11
c.config.key2 => 12
c.config.key3 => 13
c.config.dir1.key1 => 1
c.config.dir1.key2 => 2
c.config.dir1.key3 => 3
c.config.dir1.key4 => nil

Applying Multiplexers

A multiplexer groups multiple config values and uses the result of a supplied code block to choose the appropriate one. Multiplexers can be static or dynamic. A static multiplexer is evaluated when it is created and its result replaces the key group specified. A dynamic multiplexer is evaluated every time it's called. Multiplexers are static by default.

Global

c = ConfigLogic.new('path/to/config/dir', :multiplexers => [ { :name => 'key',
                                                               :selector => Proc.new {1 + 1 },
                                                               :inputs => {1 => :key1, 2 => :key2, 3 => :key3} } ] )
c.config.key => 2
c.config.key1 => nil
c.config.key2 => nil
c.config.key3 => nil
c.config.dir1.key => 2
c.config.dir1.key1 => nil
c.config.dir1.key2 => nil
c.config.dir1.key3 => nil

Local

c.config.insert_multiplexer({ :name => 'key',
                              :selector => Proc.new {1 + 1 },
                              :inputs => {1 => :key1, 2 => :key2, 3 => :key3} })
c.config.key => 2
c.config.key1 => nil
c.config.key2 => nil
c.config.key3 => nil
c.config.dir1.key => nil
c.config.dir1.key1 => 1
c.config.dir1.key2 => 2
c.config.dir1.key3 => 3

Static vs Dynamic

A dynamic multiplexer will re-evaluate the selecor proc every time it's called

c.config.insert_multiplexer({ :name => 'key',
                              :static => false,
                              :selector => Proc.new { rand(3) + 1 },
                              :inputs => {1 => :key1, 2 => :key2, 3 => :key3} })
c.config.key => 2 = time = 0
c.config.key => 1 = time = 0 + n

Credits

Inspired by RConfig (Rahmal Conda) / activeconfig (Enova Financial)