When to use Environment Vars vs CfnParameter?

[Nikola-Milovic]

Hello everyone, new to the CDK and cloud formation in general, I was just wondering, when do we use process.env vs CfnParameter? Accessing process variables just seems much easier, what would be the use case between these two? I know that process.env is available during synth and the CfnParameter are only available during deployment, but not sure what is the correct use case for them. When do I choose one over the other?

[chrisandrewcl]

Using CloudFormation parameters in CDK is usually discouraged, but it really depends on your use case.

E.g.:

• Are you using CDK to generate parameterizable templates that are later used by other people to feed them directly into CloudFormation? This might be a valid use case for CfnParameters.
• If not, you might be better off using environment variables or CDK context.

[Nikola-Milovic]

@chrisandrewcl That makes sense, thanks!

But this begs another question, context vs env variables? Any rules around those, or is it preference mostly? I saw that Context does some caching or something but not quite sure how that affects my development

[chrisandrewcl]

Both env vars and context will have the same results, so yes, I think it comes down to preference. Also, there's nothing to stop you from combining these approaches if you wish.

Having experimented with context parameters in a few projects, I prefer env vars:

• They are a common standard and are used everywhere for development and deployment.
• Locally, you can configure them just once in your console or load them with dotenv instead of typing long CLI calls with lots of context variables.
• When automating (e.g. on a CICD server) you can simply load them directly rather than somehow mapping them to context CLI parameters.

* Just for completeness, these are primarily for parameters in the "build" scope (e.g. defining small variations of your infrastructure). It's best not to use them for secrets and runtime settings, which are better handled by services like Secrets Manager, SSM Params, and AppConfig.

[Nikola-Milovic]

Thanks for such a clear answer. Now I have a much better understanding and can keep working on my project

[github-actions[bot]]

Hello! Reopening this discussion to make it searchable.