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Lambda Packager

Lambda Packager builds your project's npm packages for use on AWS Lambda using AWS Lambda.

Motivation

AWS Lambda runs Node.js apps, but you have to provide the node_modules directory yourself. Building it on your local machine won't work if your dependencies contain native code that needs to be compiled. Amazon suggests running an EC2 instance, compiling the dependencies there manually, then copying them back to your machine over SSH.

Lambda Packager makes deploying Node.js code to AWS Lambda easy, by using Lambda itself to compile your dependencies.

Just provide Lambda Packager with a directory containing your Lambda function (it must contains a package.json file with a list of dependencies), and it will build a zip file of that directory with a Lambda-compatible node_modules directory that's ready to deploy.

Usage

Note: You must deploy the Lambda builder before these commands will work. See Deployment.

Command Line

lambda-packager package my-package output.zip

Programmatic

var lambdaPackager = require('lambda-packager');

lambdaPackager.build({
  from: 'my-package',
  to: 'output.zip'
});

Assuming my-package is a path to a directory with a package.json file, its dependencies will be compiled via Lambda, then the package plus the dependencies will be placed into my-package-function.zip.

Deployment

To build dependencies, Lambda Packager uploads your package.json to a Lambda function that builds your dependencies in the AWS environment.

To deploy this builder function to AWS, run the lambda-packager deploy command, which will prompt you for the name to use for the CloudFormation stack, as well as what region to create it in. It will automatically use the same credentials as the AWS CLI.

This command builds a CloudFormation stack that provisions everything needed to build dependencies for Lambda Packager:

  • IAM Role
  • Lambda Function
  • S3 Bucket

Make sure that the AWS account you have authorized via the AWS CLI has permission to create each of these resources.

Example

Imagine I have a Node.js Lambda function that I want to deploy. It's file structure looks like this:

simple-package
├── index.js
└── package.json

Your package.json contains a list of dependencies, like this:

{
  "dependencies": {
    "contextify": "0.1.14"
  }
}

contextify contains native code, so if I run npm install on my computer and upload my project to Lambda, it won't work. Instead, I'll use lambda-packager to build it:

lambda-packager package simple-package simple-package-lambda.zip

After a few seconds to a few minutes (depending on the number of dependencies), the package command will produce the simple-package-lambda.zip file in my current directory. That zip file, if expanded, would look like this:

simple-package
├── index.js
└── package.json
└── node_modules
    └── contextify

Because the zip file is just your package with a Lambda-compatible node_modules directory, it's ready to upload to your Lambda function, either via the AWS CLI, the AWS console, or via another tool.

How It Works

diagram of lambda packager architecture

npm packages written in pure JavaScript run fine on Lambda, but many packages contain native code (written in C or C++) that must be compiled. If you build those dependencies on your local machine, they're unlikely to work on the custom version of Amazon Linux that powers AWS Lambda.

Lambda Packager works by invoking a Lambda function running on AWS and uploading your project's package.json to it. It copies that package.json to a temporary directory, then runs npm install to compile the dependencies in the Lambda environments

Once compilation is complete, it uploads the Lambda-compatible dependencies to S3. Those dependencies are then downloaded back to your local machine.

To facilitate deployment, Lambda Packager will create a copy of your Node package, copy in the Lambda-built node_modules directory, and create a zip file that is ready to deploy via the AWS console or CLI utility.

Thanks

Lambda Packager was inspired by the Thaumaturgy project. I wanted to make something more automated that used my projects' package.json, rather than specifying dependencies manually. I also wanted something that bundled everything into a ready-to-deploy zip.

Work on this project is generously sponsored by Bustle Labs.