@interval/envoy

🚛 Envoy

Envoy gives your TypeScript apps type safe access to environment variables.

Envoy accepts an envoy.config.ts file and an .env file as input and generates a single env.ts file which exports a constant for each variable as output.

There are a few major benefits to this approach:

1. You no longer need to keep track of what environment variables + secrets your app needs to run. Your envoy.config.ts defines them all.
2. By adding a envoy step before starting your app, you can prevent it from starting/deploying unless all required environment variables are present.
3. Because envoy generates a .ts env file, you get full editor support and static type checking. Mistyping a variable name will result in a compile time error, not a mysterious runtime bug.

Getting Started

1. Install Envoy

Using yarn:

yarn add @interval/envoy

1. Create your config + .env files

You'll next need to create an Envoy config file. This defines the variables that Envoy will expect.

⚙️ envoy.config.ts

import { EnvoyVariableSpec } from '@interval/envoy'

const vars: EnvoyVariableSpec[] = ['DATABASE_URL', 'STRIPE_API_KEY']

export default vars

Commit this to your repo!

🔐 .env

This is a standard .env file in KEY=VALUE format. Each key in this file should correspond to what you've defined in envoy.config.ts.

The values in this file are either secrets which you can't commit or environment specific configuration details which you shouldn't.

DATABASE_URL=postgres://[e-mail]:5432
STRIPE_API_KEY=sk_test_123456789101112131415

Don't commit this file!

1. Run envoy!

Running yarn envoy will look for a .env and envoy.config.ts file in your current working directory and will output an env.ts file that looks like this:

// THIS FILE WAS AUTOMATICALLY GENERATED BY ENVOY
// TO ADD A NEW ENVIRONMENT VARIABLE, RUN ENVOY
// DO NOT EDIT THIS FILE DIRECTLY

const DATABASE_URL = 'postgres://[e-mail]:5432'
const STRIPE_KEY = 'sk_test_123456789101112131415'

export { STRIPE_KEY, DATABASE_URL }

You can use this like any other TypeScript file. Just be sure that you don't commit this file as it contains your secrets that you defined manually in your .env file.

Behavior

If you define a variable in .env but exclude it from your envoy.config.ts, the resulting env.ts file will not contain that variable.

If you define a variable in envoy.config.ts, but don't define it in your .env, Envoy will fail and will exit with code 1.

Recommended usage

We suggest you run yarn envoy each time your app compiles. For example, at Interval, our yarn start:dev command runs yarn envoy && yarn ts:node.

Note that this library effectively hard codes your secrets into each build. Depending on your infrastructure, this may be a non-starter.