lazyConfig 0.2.2

lazily loading and overriding configuration for the lazy coder

lazyConfig

lazily loading and overriding configuration for the lazy coder

lazyConfig is an opinionated configuration provider. Loading .yml, .yaml or .json configuration files. Opinionated since it requires you to structure your configuration in a certain way in order to work.

Why lazyConfig?

see Motivation

Usage

In order to load your configuration folder into a dict like structure, simply point lazyConfig to the folder

from lazyConfig import Config

config = Config.from_path(
    config='/path/to/default/config',
    '/path/to/override',
    '/path/to/another/override/',
    ...
)

# or with environment variables:

config = Config.from_env(config='DEFAULT_CONFIG_ENV_VAR', 'OVERRIDE1', ...)

where the environment variables should contain the path to the configuration directories. Files are overriden left to right (i.e. the last argument has priority)

you can mix and match using Config.from_path and os.environ[ENV_VAR]

Assumptions about the file structure

Since filenames are used as keys in the config dict, without any caveats you would be forced to have a minimum depth of 1 for any configuration.

This might not make sense for some high level, flat configuration. For this reason there is a special filename __config__ (.yml,.yaml or .json), which allows you to define top level keys and values.

Example

config
    database
        configuration.yml
        __config__.yml
    app.yml
    __config__.yml

config/__config__.yml:

name: my-app
author: ME!
version: -1.0

app.yml:

primary_color: 'blue'
secondary_color: 'green'

config/database/__config__.yml:

connection:
    hosts:
        - {host: "myElasticsearchServer", port: 9200}
    timeout: 6000

config/database/configuration.yml:

indices:
    index1: {...}
    index2: {...}
pipelines:
    pipeline1: {...}

would be loaded as the following dictionary (formatted in yml for readability):

name: my-app
author: ME!
version: -1.0
app:
    primary_color: 'blue'
    secondary_color: 'green'
database:
    connection:
        hosts:
            - {host: "myElasticsearchServer", port: 9200}
        timeout: 6000
    configuration:
        indices:
            index1: {...}
            index2: {...}
        pipelines:
            pipeline1: {...}

So you could access index1 with:

config.database.configuration.indices.index1

Duplicate Keys

Duplicate Keys are not allowed. lazyConfig tries to find keys in

1. Keyfiles (__config__)
2. Filenames
3. Directories

in that order! It will not keep looking whether or not there is a duplicate and thus ignore a directory if a file with the same name (sans extension) or a key with the same name in the keyfile exists.

There might be a configuration validation function in the future to check for duplicate keys (in debug mode or on manual call)

Attribute access

Python does not allow attributes to start with a number. So

config.1attribute2breakthings

will not work. In these cases you will have to use

config['1attribute2breakthings']

Lists

Lists are overriden not extended. If the default configuration has the same key for a list as an override, then the default list is ignored and the override is used.

Extending Lists would mean that you can not remove elements with a configuration override. As this is not desirable you will just have to duplicate lists in its entirety if you want to change them (even if only slightly)

Since numbers are discouraged anyway, you can define Directory Lists like this:

config
    list
        0.yml
        1.yml
        2.yml
        3.yml

which is then converted to

config:
    list:
        - {content from 0.yml}
        - {content from 1.yml}
        - {content from 2.yml}

Directory Lists must start with 0 and end with n-1 where n is the number of files in the directory.

It is currently not possible to create a list of directories (instead of files). This might become a feature in a future version if requested

Security

Using pyYAML.unsafe_load(), lazyConfig is currently not meant for external data.

Future Features

things which I might get around to do some time:

• other configuration languages/parsers (e.g. TOML, safe config loaders, etc.)
• Configuration Validation
• Horizontal override (Templates, e.g. for indices)
• Configuration Setter

  Since it is not obvious where to set directory/file boundaries inside the dictionary, this is not as trivial as it might seem at first. It might be necessary to provide the grouping level as an argument.

• generate JSON Schema from default configuration

Versions

• 0.2.2 fix equality
• 0.2.1 fix broken iterator
• 0.2 Config implements Mapping
• 0.1.1 handle NULL environment variables
• 0.1: basic proof of concept