checkenv

Don't get surprised by your environment variables.

Rationale

At Bugout, we configure our applications using environment variables. This follows the Twelve Factor App methodology and generally serves us well.

Still, there are many ways to pass environment variables to an application process. For example, we store environment variables on AWS Systems Manager Parameter Store and on Google Cloud Secret Manager. When we deploy applications to our servers, the first step is to download these environment variables from the cloud store and write them to environment files. We then pass these environment files to the systemd services responsible for running the applications using the EnvironmentFile parameter.

In our development environments, we have files that are very similar to the systemd environment files, except they explicitly export the environment variables. We source these environment files before we run the development versions of our applications.

It can sometimes be difficult to understand:

1. Whether all the environment variables we expect to be defined in production actually have been.
2. What the particular value of a production environment actually is.
3. What the differences are between our expectations and the actual environment variables in a running application process.

We are building and maintaining checkenv to make it easier for us to diagnose and fix issues with application configuration via environment variables. We stand in solidarity with anyone else who experiences these kinds of issues. We are doing this for you, too! :)

Architecture

Because environment variables can come from different providers - an active shell, an environment file, a cloud configuration store - checkenv allows environment providers to be registered at build time using build tags.

This means that you can write a custom environment provider for checkenv and build a custom checkenv binary which supports your needs.

There is currently no need to support runtime plugins. Since doing so would make this program a lot more complicated, we have decided to forego runtime plugin functionality for now.

Usage

./checkenv plugins

Available plugins:

• env - Provides the environment variables defined in the checkenv process.
• file - Provides the environment variables defined in the env file with the given path.
• proc - Provides the environment variables set for the process with the given pid.
• aws_ssm - Provides environment variables defined in AWS Systems Manager Parameter Store.

aws_ssm plugin

In order to fetch parameters with tags Product = test and Node = true with export prefix execute following command

./checkenv show -export aws_ssm+Product:test,Node:true