parameter-store-environ 0.1.2

A simple configuration variable wrapper around AWS SSM Parameter Store

ps-environ

Description

This is a simple wrapper around AWS SSM Parameter Store. It is designed to cache and parse variables from Parameter Store for a specific service and stage. It is heavily inspired by django-environ and shares a (simplified) interface.

For more on Parameter Store, read the AWS documentation.

Installation

Install with pip:

pip install parameter-store-environ 

Usage

The wrapper assumes that variables in parameter store are in the following format: /<SERVICE>/<STAGE>/<VARIABLE_NAME>

So, for example:

/api/dev/DEBUG
/api/prod/DB_HOST

The wrapper is agnostic to the variable name, but we recommend you follow the convention for environment variables and use all caps and underscores.

In your settings/configuration module, import the module and create a new instance of the wrapper

from ps_environ import Env
config = Env(service='api', stage='dev')

# When called directly, the string value is returned
assert config('DEBUG') == 'True'

# Use casting methods to return the type you need
assert config.bool('DEBUG') == True

Schemas

You can define a schema when you instantiate the wrapper to avoid having to call the casting methods

config = Env(service='api', stage='dev', schema={
    'DEBUG': bool,
    'MAX_RETRIES': int,
})

assert config('DEBUG') == True
assert config('MAX_RETRIES') == 5

Supported casting types: bool, float, int, set, list, tuple, json

Additional Notes:

• list, tuple, set: These types expect the values to be separated by commas. E.g. 1,2,3
• json: A regular JSON string is expected. E.g. {'foo': 'bar'}

Environment Variable Override

If the variable is also set in the environment, that value will take precedence.

Default Values

You can set a default value by setting the default keyword. If no default is set and the value is neither in the environment variables or in parameter store, an ImproperlyConfigured exception will be raised.

assert config('DB_HOST', default='localhost') == 'localhost'

AWS Credentials

ps-environ uses boto3 to interface with parameter store and therefore uses the same mechanism for authentication. See the configuring credentials in the Boto 3 documentation for more information.