Loading precedence (latter overrides former):

1. Load application default settings (config/default.yml)
2. Load environment settings
3. Load custom settings

Default settings of the application is provided by the upstream, therefore, it should not be modified.

There are four types of environments: development, testing, staging and production. Environment can be set by using the shell environment variable: ENV. If the environment variable is not specified, it is set to development as default. Environment settings override default settings.

Custom settings override environment settings. The search path for custom settings is:

1. Environment variable SETTINGS
2. config/settings.yml

If both paths are not available, that means the custom settings are not specified.

config/settings.yml is a custom settings, therefore, it will be ignored by git in .gitignore file:

config/settings.yml

The complete directory structure regarding to the configuration setup:

config/
├── default.yml
├── environments
│   ├── development.yml
│   ├── production.yml
│   ├── staging.yml
│   └── testing.yml
└── settings.yml

Quick start command:

$ node app

Fully customized start command:

$ ENV=production SETTINGS=/path/to/settings.yml node app