aws-lambda-nodejs-webpack

---

CDK Construct to build Node.js AWS lambdas using webpack

Table of contents:

• Usage example
• Features
• Why?
• Roadmap
• How to make changes and test locally
• Thanks

Usage example

yarn add aws-lambda-nodejs-webpack

// infra/super-app-stack.js
const sns = require("@aws-cdk/aws-sns");
const subscriptions = require("@aws-cdk/aws-sns-subscriptions");
const core = require("@aws-cdk/core");
const { NodejsFunction } = require("aws-lambda-nodejs-webpack");

module.exports = class SuperAppProductionStack extends core.Stack {
  constructor(scope, id, props) {
    super(scope, id, props);

    const slackNotificationsLambda = new NodejsFunction(
      this,
      "slack-notifications-lambda",
      {
        entry: "events/slack-notifications.js", // required
      },
    );
  }
};

// events/slack-notifications.js
import { WebClient as SlackWebClient } from "@slack/web-api";

export function handler(event) {
  const message = event.Records[0].Sns.Message;
  // do something with message
}

Features

• fast, no-docker CDK construct
• lambda output respects original files structure and node_modules (no inlining)
• lambda output only contains the necessary files, no README, tests, ...
• bundling happens in temporary directories, it never writes in your project directory
• source map support

Why?

There's already a dedicated aws-lambda-nodejs module for CDK but I had two major issues with it:

1. CDK uses docker for anything lambda build related. This means it mounts your whole Node.js project (not just the lambda code) inside Docker before running a bundler like Parcel. This is perfectly fine and performant on Linux and Windows, but this is extremely slow on macOS: a single cdk synth would take 2 minutes for a 3 lines lambda. Since it might take a very long time for Docker on macOS to get as fast as on Linux. Even their latest update (mutagen), while significantly faster, still takes 20s just to mount a Node.js project.
2. aws-lambda-nodejs generates a single file bundle with every local and external module inlined. Which makes it very hard to debug and read on the AWS console. I wanted a lambda output that mimicks my project file organization.

I want to be clear: I respect a LOT the work of the CDK team, and especially @jogold, author of aws-lambda-nodejs) that helped me a lot into debugging performance issues and explaining to me how everything works.

Roadmap

This is a list of features I thought could be interesting to users. If you need on of them, please contribute to the project.

• Test/Get feedback on TypeScript support
• Get feedback on monorepo support
• Allow passing webpack/babel options/a function that can update the full webpack configuration
• Allow native modules/passing externals, with option nativeModules or externals. They would have to be installed into a temp folder with npm_config_arch and npm_config_platform and aliased in webpack configuration/or considered as externals. Externals and nativeModules seems related options but may be completely different
• Use jsii to build the construct for other languages
• Add tests
• (if current way buggy): force people to provide aliases instead of considering cwd as base node_module
• Allow usage without the need of entry: new NodejsFunction(this, "slack-notifications-lambda"); that would mimic https://docs.aws.amazon.com/cdk/api/latest/docs/aws-lambda-nodejs-readme.html#nodejs-function
• [ ]
• Generate a bundle where entry is moved to /main.js
• Allow using TypeScript
• use webpack and babel cache
• remove webpackconfig from bundle
• pass runtime to babel target
• cdk synth generates different builds even when the lambda code does not changes, issue?
• Allow using babel, if you need preset-env
• add babel preset env by default
• add bundling timing information to output console note: this would pollute cdk synth
• Ask CDK team if this could live under their repositories Better be just community based
• Other ideas? Open an issue

How to make changes and test locally

// fork and clone
cd aws-lambda-nodejs-webpack
yarn
yarn link
yarn start

# in another terminal and project where you want to test changes
yarn link aws-lambda-nodejs-webpack
# cdk commands will now use your local aws-lambda-nodejs-webpack

Thanks

• the CDK team for this awesome project
• @jogold for his time while helping me debugging performance issues on Docker