Amazon Lambda Node.js Library

This library provides constructs for Node.js Lambda functions.

Node.js Function

Define a NodejsFunction:

new lambda.NodejsFunction(this, 'my-handler');

By default, the construct will use the name of the defining file and the construct's id to look up the entry file:

.
├── stack.ts # defines a 'NodejsFunction' with 'my-handler' as id
├── stack.my-handler.ts # exports a function named 'handler'

This file is used as "entry" for esbuild. This means that your code is automatically transpiled and bundled whether it's written in JavaScript or TypeScript.

Alternatively, an entry file and handler can be specified:

new lambda.NodejsFunction(this, 'MyFunction', {
  entry: '/path/to/my/file.ts', // accepts .js, .jsx, .ts and .tsx files
  handler: 'myExportedFunc'
});

All other properties of lambda.Function are supported, see also the AWS Lambda construct library.

The NodejsFunction construct automatically reuses existing connections when working with the AWS SDK for JavaScript. Set the awsSdkConnectionReuse prop to false to disable it.

Lock file

The NodejsFunction requires a dependencies lock file (yarn.lock, pnpm-lock.yaml or package-lock.json). When bundling in a Docker container, the path containing this lock file is used as the source (/asset-input) for the volume mounted in the container.

By default, the construct will try to automatically determine your project lock file. Alternatively, you can specify the depsLockFilePath prop manually. In this case you need to ensure that this path includes entry and any module/dependencies used by your function. Otherwise bundling will fail.

Local bundling

If esbuild is available it will be used to bundle your code in your environment. Otherwise, bundling will happen in a Lambda compatible Docker container.

For macOS the recommendend approach is to install esbuild as Docker volume performance is really poor.

esbuild can be installed with:

$ npm install --save-dev esbuild@0

OR

$ yarn add --dev esbuild@0

To force bundling in a Docker container even if esbuild is available in your environment, set bundling.forceDockerBundling to true. This is useful if your function relies on node modules that should be installed (nodeModules prop, see below) in a Lambda compatible environment. This is usually the case with modules using native dependencies.

Working with modules

Externals

By default, all node modules are bundled except for aws-sdk. This can be configured by specifying bundling.externalModules:

new lambda.NodejsFunction(this, 'my-handler', {
  bundling: {
    externalModules: [
      'aws-sdk', // Use the 'aws-sdk' available in the Lambda runtime
      'cool-module', // 'cool-module' is already available in a Layer
    ],
  },
});

Install modules

By default, all node modules referenced in your Lambda code will be bundled by esbuild. Use the nodeModules prop under bundling to specify a list of modules that should not be bundled but instead included in the node_modules folder of the Lambda package. This is useful when working with native dependencies or when esbuild fails to bundle a module.

new lambda.NodejsFunction(this, 'my-handler', {
  bundling: {
    nodeModules: ['native-module', 'other-module'],
  },
});

The modules listed in nodeModules must be present in the package.json's dependencies or installed. The same version will be used for installation. The lock file (yarn.lock, pnpm-lock.yaml or package-lock.json) will be used along with the right installer (yarn, pnpm or npm).

When working with nodeModules using native dependencies, you might want to force bundling in a Docker container even if esbuild is available in your environment. This can be done by setting bundling.forceDockerBundling to true.

Configuring esbuild

The NodejsFunction construct exposes some esbuild options via properties under bundling:

new lambda.NodejsFunction(this, 'my-handler', {
  bundling: {
    minify: true, // minify code, defaults to false
    sourceMap: true, // include source map, defaults to false
    target: 'es2020', // target environment for the generated JavaScript code
    loader: { // Use the 'dataurl' loader for '.png' files
      '.png': 'dataurl',
    },
    define: { // Replace strings during build time
      'process.env.API_KEY': JSON.stringify('xxx-xxxx-xxx'),
      'process.env.PRODUCTION': JSON.stringify(true),
      'process.env.NUMBER': JSON.stringify(123),
    },
    logLevel: LogLevel.SILENT, // defaults to LogLevel.WARNING
    keepNames: true, // defaults to false
    tsconfig: 'custom-tsconfig.json', // use custom-tsconfig.json instead of default,
    metafile: true, // include meta file, defaults to false
    banner : '/* comments */', // requires esbuild >= 0.9.0, defaults to none
    footer : '/* comments */', // requires esbuild >= 0.9.0, defaults to none
  },
});

Command hooks

It is possible to run additional commands by specifying the commandHooks prop:

new lambda.NodejsFunction(this, 'my-handler-with-commands', {
  bundling: {
    commandHooks: {
      // Copy a file so that it will be included in the bundled asset
      afterBundling(inputDir: string, outputDir: string): string[] {
        return [`cp ${inputDir}/my-binary.node ${outputDir}`];
      }
      // ...
    }
    // ...
  }
});

The following hooks are available:

• beforeBundling: runs before all bundling commands
• beforeInstall: runs before node modules installation
• afterBundling: runs after all bundling commands

They all receive the directory containing the lock file (inputDir) and the directory where the bundled asset will be output (outputDir). They must return an array of commands to run. Commands are chained with &&.

The commands will run in the environment in which bundling occurs: inside the container for Docker bundling or on the host OS for local bundling.

Customizing Docker bundling

Use bundling.environment to define environments variables when esbuild runs:

new lambda.NodejsFunction(this, 'my-handler', {
  bundling: {
    environment: {
      NODE_ENV: 'production',
    },
  },
});

Use bundling.buildArgs to pass build arguments when building the Docker bundling image:

new lambda.NodejsFunction(this, 'my-handler', {
  bundling: {
      buildArgs: {
        HTTPS_PROXY: 'https://127.0.0.1:3001',
      },
  }
});

Use bundling.dockerImage to use a custom Docker bundling image:

new lambda.NodejsFunction(this, 'my-handler', {
  bundling: {
    dockerImage: cdk.DockerImage.fromBuild('/path/to/Dockerfile'),
  },
});

This image should have esbuild installed globally. If you plan to use nodeModules it should also have npm, yarn or pnpm depending on the lock file you're using.

Use the default image provided by @aws-cdk/aws-lambda-nodejs as a source of inspiration.