environment-settings 0.0.3

Environment specific management of application configuration

Environment Settings

The environment_settings package allows applications to manage multiple runtime environment configurations in a central location using settings stored as normal python modules. Inspired by the [Django settings framework] (https://docs.djangoproject.com/en/dev/ref/settings/), the settings are loaded dynamically using a context manager at the application entry point. Additionally, the environment_settings module provides a decorator that can be used to load the correct settings for automated tests.

Usage

The following guide shows a typical application structure with support for multiple environment configurations. The conf package contains configuration files for each environment.

my-app
|--my_app
|  |--conf
|  |  |--__init__.py
|  |  |--dev.py
|  |  |--uat.py
|  |  |--unittest.py
|  |  `--prod.py
|  |--app.py
|  `--lib.py
|--tests
|  `--unittests
|     `--test_lib.py
|--pyproject.toml
|--README.md
`--setup.py

Settings package configuration

Add the following code to the packge __init__.py to mark it as "settings enabled"

# my_app/conf/__init__.py
from environment_settings import Settings

settings = Settings(package=__name__)

Settings file layout

Each settings file are implemented as normal python modules. Settings should be UPPERCASE as per the example below. Any other python code will not be visible in the settings context.

# my_app/conf/dev.py
GOOD_SETTING_EXAMPLE = 'I am visible'
bad_setting_example = 'I am not visible'

Initialising the settings context at the application entry point

Before any setting can be used, the settings context needs to be activated. Failure to active the context will result in an ImproperlyConfigured exception

# my_app/app.py
from my_app.conf import settings

with settings.environment('dev'):
    print(settings.GOOD_SETTINGS_EXAMPLE)

# Out[0]: 
# I am visible

print(settings.GOOD_SETTINGS_EXAMPLE)

# Out[1]:
# Traceback (most recent call last):
# ...
# ImproperlyConfigured: Requested GOOD_SETTINGS_EXAMPLE, but settings are not configured. You must define the settings.environment(name)

Using settings throughout the application

The centralised settings object can be imported anywhere throughout the application:

# my_app/lib.py
from my_app.conf import settings

def my_func():
    return settings.GOOD_SETTINGS_EXAMPLE

Testing

environment_settings also provides a decorator that can be used to provide test specific settings in test cases:

# my_app/conf/unittest.py
GOOD_SETTINGS_EXAMPLE = 'unittest example'

# tests/unittests/test_lib.py
from my_app.conf import settings
from my_app import lib

@settings.environment('unittest')
class TestLib:
    def test_lib(self):
        assert lib.my_func() == 'unittest example'