figtion

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`---^-^--^--^---`--' hjw

A simple configuration interface with plaintext and encrypted file support.

Benefits

• seemless Python dict interface
  • unified config definition and defaults
• YAML text file source for file-system input & serialization
  • nested entries supported
  • optional live reloading
• simple precedence
  • defaults keys define config keys
  • YAML values override defaults values
• secrets support
  • secrets saved to private YAML file
  • secrets encrypted at rest via environment variable
  • update & mask from public YAML file

Examples

Config Definition and Defaults

import figtion

defaults = {'my server'       : 'www.bestsite.web'
           ,'number of nodes' : 5
           ,'password'        : 'huduyutakeme4'
           ,'nested stuff'    : {'breakfast' : 'coffee'}
           ,'listed stuff'    : ['a','b','c']}

cfg = figtion.Config(defaults=defaults,filepath='./conf.yml')

print(cfg['my server'])  

This will print either 'www.bestsite.web' or the value of 'my server' in ./conf.yml if it is something else.

defaults strictly defines the schema. Only keys present in defaults from a serial file will be retained. If you want to risk unspecified input keys and load everything from the YAML file, you can either omit the defaults parameter or set promiscuous=True when constructing Config.

Self-Documenting Plaintext

Specify if/when you want to update stored plaintext file.

cfg = figtion.Config(..., promiscuous=True)
...
cfg.dump()

If concise=True, only modified values are stored in text file. If promiscuous=False (default behavior), deprecated values are quietly removed. Otherwise, serialized YAML will clarify default, modified, and deprecated values:

##############################
####       Modified       ####
##############################
my server: www.newsite.web


##############################
####       Default        ####
##############################
number of nodes: 5


##############################
####      Deprecated      ####
##############################
fave cat: Zelda

Dynamic Reloading

cfg = figtion.Config(defaults=defaults, filepath='./conf.yml', reload_interval=5)

# ...some time later, after ./conf.yml has been edited externally...
value = cfg['my server']   # triggers an mtime check; reloads if changed

if cfg.changed:
    # propagate the new values to your application, then clear the flag
    restart_workers()
    cfg.changed = False

reload_interval is in seconds and defaults to 5. Pass 0 to check on every read, or None to disable dynamic reloading entirely. The changed flag is only set when an actual value differs after reload. Touching the file without changing content will not flip it.

Config Secrets

When you want a public config file and a separate secret one. To keep secret encrypted "at rest", set a secret key environment variable FIGKEY.

os.environ["FIGKEY"] = "seepost-itnote"

cfg = figtion.Config(defaults=defaults,filepath='./conf.yml',secretpath='./creds.yml')
cfg.mask('password')

print(cfg['password'])

This will print the value of 'password', which is stored in ./creds.yml and not ./conf.yml. If the value of 'password' is changed in either YAML file, the password will be updated in ./creds.yml and masked from ./conf.yml the next time the class is loaded in Python. If a secret key is present via environment variable FIGKEY, the values in ./creds.yml will be encrypted using that key. The dictionary object returned for cfg contains the true value.

If you want everything treated as secret, provide a secretpath and omit filepath:

cfg = figtion.Config(secretpath='./creds.yml')

In this case, no call to mask is needed and everything is encrypted at rest.

Encryption Details

This uses the pynacl bindings to the libsodium library, which uses the XSalsa20 algorithm for encryption. The encryption key provided by the FIGKEY environment variable is truncated to a 32-byte string.