I’ve recently settled on a clever use of to prep AWS Lambda Functions for deployment. I’d like to tell you how I’m using NPM and why it’s better than Webpack or Serverless Framework. npm pack If you’re deploying JavaScript to AWS Lambda you’re likely aware there’s more than one way to do it. JavaScript and Serverless do not suffer from a lack of packaging tools. So far I’ve tried: Serverless Serverless + Webpack plugin + Babel SAM + Webpack SAM + NPM (lately) Why I use SAM instead of Serverless Serverless Framework is great if you’re new to the AWS ecosystem, especially CloudFormation. It also manages packaging and deployment of your JavaScript. After some time with Serverless I discovered a few things: I found myself guessing about the specific CloudFormation Serverless would generate I became concerned that I didn’t understand it was generating what it was why Many plugins jump outside of CloudFormation and use the AWS SDK. This can result in config that is not idempotent I found Serverless’ lifecycle hooks for plugins were not well documented I had to learn CloudFormation anyway so I could configure the resources I needed Over time I found most of my Serverless YAML was hand-written CloudFormation SAM abstracts only the most tedious bits of CloudFormation so I know what’s going on in there In a nutshell, SAM offers me the right level of visibility and control. Why I’m not using Webpack + Babel This is simple: . Yes, Webpack + Babel produce sourcemaps. Yes, Babel lets you use new language features. Yes, Webpack can produce lean packages. Here’s how things work for me in practice: debugging Theres , except by editing your code in the AWS console. If you’re redeploying between runs you’ll never get there a whole class of bugs that cannot be understood in a reasonable amount of time The output of Webpack and Babel are not intended to be human readable. Good luck working in a tight feedback loop in the console Lambda supports Node 8.10 which has good enough coverage of the latest language features. The only “big” features 8.10 lacks are async generators and for-await-of. In my experience, a tiny fraction of Node developers understand how to use these features properly Thus, I stick to the language features available in Node 8.10 and I don’t use Babel. For a list of Node 8.10's working features see Node 9.11.2 in . Node.green Why I use NPM instead of Webpack Why might I use Node Package Manager to package JavaScript to run on Node? The possibilities abound. npm pack NPM has a command called “pack” which It’s much easier to use than Webpack. builds a package of everything you want and none of what you don’t want. By default grabs everything except: npm pack What’s in .npmignore What’s in node_modules To include dependencies from add them (explicitly) to the key in . No more Googling “webpack node externals aws-sdk”. NPM will trace the dependencies of the packages you deem necessary and add them to your package. node_modules bundleDependencies package.json bundleDependencies in package.json There’s also a handy flag . For example, will add axios to at install time. -B npm install -B axios bundleDependencies Here’s what output looks like: npm pack Output from ' ' npm pack TAR to ZIP Here’s the wrinkle: produces a TAR and Lambda expects a ZIP. In addition, NPM places everything under . This is a simple fix in the NPM script in . The script is called after . For more info on NPM pre/post scripts see . npm pack package/ postpack package.json postpack pack this page "postpack": "tarball=$(npm list — depth 0 | sed ‘s/@/-/g; s/ .*/.tgz/g; 1q;’); tar -tf $tarball | sed ‘s/^package\\///’ | zip -[@r](http://twitter.com/r "Twitter profile for @r") package; rm $tarball" Postpack script in package.json Now we’ll get a each time we run . package.zip npm pack If you aren’t big on shell commands this one can look daunting. I promise it’s not that bad. Here’s an explanation of what it does. First, we figure out the name of the TAR file, without running again ( ). We can’t run in (even though it gives us the file name) because it’ll cause a recursive loop. npm pack explain-shell npm pack postpack tarball=$(npm list — depth 0 | sed ‘s/@/-/g; s/ .*/.tgz/g; 1q;’); Next, we take everything in the tar file and put it in ( ). package.zip explain-shell tar -tf $tarball | sed ‘s/^package\\///’ | zip -@r package; Finally, we delete the tar file ( ). explain-shell rm $tarball You don’t have to leave the script as a long one-liner in , feel free to pull it out into a bash file and make it more readable. package.json Deploy Have a look at the I created for this article, particularly . sample repository this commit git clone [https://github.com/ryanwmarsh/sam-with-npm](https://github.com/ryanwmarsh/sam-with-npm) cd sam-with-npm/hello_world npm install npm pack cd .. aws s3 mb s3://sam-with-npm sam package --template-file template.yaml --output-template-file packaged.yaml --s3-bucket sam-with-npm sam deploy --template-file packaged.yaml --stack-name sam-with-npm --capabilities CAPABILITY_IAM aws cloudformation describe-stacks --stack-name sam-with-npm --query 'Stacks[].Outputs' Output of ‘describe-stacks’ Finally, check it with your endpoint curl https://xxxxxxxxxx.execute-api.us-east-1.amazonaws.com/Prod/hello/ Closing I hope you found that this simplifies your tooling and workflow. If you have any questions about Serverless or DevOps I’m a freelance coach and I help teams reach maximum development output with minimal pain. You can always find me at or ryan@thestack.io http://thestack.io
