rfc2119 for keywords

PURPOSE

• to provide unified way to configure python2 and python3 application
• to be handy for developers, devops, QA and users with technical background

READINGS

• yaml tutorial
• http://yaml.org/spec/1.1/
• YAML IS NOT A JSON AND NOT A DATA SERIALIZATION FORMAT. ITS A OBJECT SERIALIZATION FORMAT

REQUIREMENTS

1. MUST support yaml out of the box
2. MUST configure program (standalone module or python package) by recursive merge developer defined configuration (defaults) and runtime provided configuration.
3. each configuration layer (e.g. defaults, runtime config, etc.) MUST be a nested mapping
4. number of merged layers is unlimited and MAY be redefined by developer
5. layer merge order MAY be redefined by developer
6. MUST contain set of yaml constructors
   • !url
   • !date
   • !datetime
   • !timedelta
   • !strjoin
   • !envvar
   • !regexp
   • !filecontent
7. SHOULD contain set of dangerous yaml constructors
   • !file
   • !socket
   • !yamlfile - includes yaml by file path or url
8. MAY process constructors with recursion detection (see REQUIREMENT NOTES)
9. MAY contain cli arg mapping constructors
10. SHOULD provide a way to extend set of constructors before configuration loaded
11. MUST provide a way to configure logging using logging.dictConfig and values from merged configuration
12. runtime configuration path MAY be redefined with envvar (like $ CONFIG=./some-config.yml program.py)
13. runtime configuration path MAY be redefined with cli arg (like $ program.py --config=./some-config.yml)
14. SHOULD enable sharing of anchors between layers
15. SHOULD NOT allow to redefine anchors that alredy defined in previous layers
16. MUST support filesystem path as configuration path
17. MUST support file://, http(s):// urls as configuration path
18. MAY support ftp:// urls as configuration path
19. MAY support git:// urls as configuration path

REQUIREMENT NOTES

• !class, !object, and !yamlfile are considered dangerous since class or object creation may require existing configuration that is not exists during constructor call. !yamlfile can refer !class or !object inside and/or cause infinte yaml load recursion or module load recursion.
• !file and !socket are considered dangerous since they are not serializable

IMPLEMENTATION

• provides <module>.<config> submodule that contains resulting configuration as mapping

???