aws-lambda-s3-dotenv

AWS's Lambda functions are incredibly powerful constructs for any cloud architecture. Coupled with versions and aliases, Lambda is well-suited for many use cases.

However...

Since environment variables are tied to a function's version, and not its alias, it makes it really difficult to do things like use the same Lambda function but point it at different environments (e.g. Dev, QA, Prod). Barring this functionality, this module will read configuration from an S3 bucket, store it in a path you specify (inside of /tmp), and either read the config from the filesystem cache, or refresh from S3.

A common way of loading configurable environment variables is the popular module dotenv. As such, this module will first check to see if there's a .env file in a cache location you specify (again, this should be prefixed with /tmp if you are running this on Lambda, as this is the only writable filepath). If it cannot find a local file to use, it will fetch a file from S3 and save it to the cache location.

TIP: It is helpful to pass the cache location as an environment variable separate from dotenv, as you can use something like CONFIG_LOCATION = .env for development on your local machine and CONFIG_LOCATION = /tmp in Lambda.

NOTE:: The localPath passed into the module should be relative to the root of your project. For example, if you are trying to load a file located at project/subdir/.env and your source file is located at project/subdir/index.js, your localPath should be ./subdir/.env, as opposed to ./.env or similar.

Installation

npm install aws-lambda-s3-dotenv

Usage

const loadConfig = require("aws-lambda-s3-dotenv");

exports.handler = function (event, context, callback) {
    let cacheLocation = ".env";
    loadConfig(cacheLocation, "s3-bucket", "s3-bucket-key", function(err) {
        if (err) console.log(err);
        else {
            require('dotenv').config({path: cacheLocation});

            // Do stuff with your environment variables
            
            callback();
        }
    });
}

Tests

npm test