Access defined runtime environment variables from powertools

[Fahadmo]

Is your feature request related to a problem? Please describe.

AWS Lambda has defined runtime environment variables as shown here: https://docs.aws.amazon.com/lambda/latest/dg/configuration-envvars.html#configuration-envvars-runtime

In order to get the name of the variable we often need to go back to the documentation which can be frustrating.

Describe the solution you'd like

I would like to have something that would let me access all defined environment variables.
For example, this could be a class with a list of cached properties for each defined runtime variable.

@cache 
@property
def AWS_REGION(self):
    return os.environ.get("AWS_REGION")

Describe alternatives you've considered
Currently, we just run the following for each environment variable we need.

x = os.environ.get(<ENV VARIABLE NAME>)

[michaelbrewer]

@heitorlessa :)

I would like this by like this: https://www.starlette.io/config/

[saragerion]

@Fahadmo personally speaking, I think this idea is brilliant. Thanks for sharing it with us.

AppConfig is outside the scope of this issue, but curious to hear about how do you see this functionality working together with AppConfig (another configuration source for Lambda)?
https://aws.amazon.com/blogs/mt/introducing-aws-appconfig-lambda-extension-deploying-application-configuration-serverless/
Asking this not bring this AppConfig functionality into this issue, but just to understand better what is the desired DX considering that there might be more than 1 data source in the future.

[michaelbrewer]

@heitorlessa - So far i have found a couple interesting libraries as an inspiration for a simple framework for environment variables, defaults (.env or json settings) and parameters (appconfig, ssm, secrets manager etc..):

• python decouple and prettyconf - what i like about these libraries is how simple and lightweight they are. Prettyconf does have an example of using SSM.
• Starlette - config - is much like python decouple.
• dynaconf is super fancy and allows for nested properties and automatic type casting.

Personally i kind of likely the simpler prettyconf or Starlette - config api:

config = Configuration(loaders=[Environment(), EnvFile(filename=env_file), ParameterStore(), ...])
DEBUG = config('DEBUG', cast=bool, default=False)
DATABASE_URL = config('DATABASE_URL', cast=databases.DatabaseURL)
SECRET_KEY = config('SECRET_KEY', cast=Secret)
ALLOWED_HOSTS = config('ALLOWED_HOSTS', cast=CommaSeparatedStrings)

• loaders - could be environment then a json config file. Or SSM Parameter Store and then environment variables.
• cast - could be list, dict, json etc..

[ran-isenberg]

For people who use the parser and pydantic, there's already a very simple solution.
You can see the implementation here: https://isenberg-ran.medium.com/aws-lambda-environment-variables-best-practices-f760384c23ed. I have a branch and tests ready to go if you want.
It does not require adding any new libraries or dependencies.

Pydantic also has support for secrets and loading configuration from files.

Just a thought ;)
@heitorlessa

[michaelbrewer]

Simple but I want a zero dependency version.

[ran-isenberg]

So you dont want to add prettyconf or Starlette ? just implement a leaner version?

[michaelbrewer]

no. just the UX.

[michaelbrewer]

"couple interesting libraries as an inspiration for a simple framework"

[ran-isenberg]

I respect that.
I'm usually on the other side - I will add external dependencies if they are reliable, have good docs, the UX is great and somebody is maintaining them. If that does not exist, I will write the code myself.

[michaelbrewer]

i don't see the need for 70mb dependency i don't want for a simple environment utility which can be performs using vanilla python 3.7+. When a lambda is >5mb in size the performance drops too much for me use case.

Hopefully v2 of powertools is closer on the roadmap to allow for even smaller lambdas.