Node.js Lambda Tracing and Bundlers Compatibility

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Overview

Datadog’s tracing libraries (dd-trace) are known to be not compatible with bundlers, like Webpack or esbuild, due to the use of conditional imports and other issues. While bundlers cannot build dd-trace, your application can still use the dd-trace and datadog-lambda-js libraries provided by the prebuilt Datadog Lambda layer. Follow the instructions below.

Webpack

Follow the installation instructions for Node.js and ensure the Datadog Lambda layer for Node.js is added to your Lambda function.
Exclude datadog-lambda-js and dd-trace, either by removing them from your package.json or by setting an exclude rule. Excluding them tells the bundler to skip building them as dependencies, since they are already available in the Lambda runtime provided by the Datadog Lambda layer.

Mark your dependencies as externals. This tells the bundler to exclude them from the output bundle; instead, they are packaged in node_modules.

webpack.config.js

const nodeExternals = require("webpack-node-externals");

module.exports = {
  // Use webpack-node-externals to exclude all node dependencies.
  // You can manually set the externals too.
  externals: [nodeExternals()],
  module: {
    rules: [
      {
        // Provided by the Datadog Lambda layer and the Lambda Runtime.
        exclude: [
          // AWS SDK v3
          /^@aws-sdk.*/,
          // AWS SDK v2
          /aws-sdk/,
          /datadog-lambda-js/,
          /dd-trace/
        ],
      }
    ]
  },
}

If you are using the serverless-webpack plugin and have the option includeModules set to any value other than false, the plugin automatically packs external modules under node_modules. Therefore, you must force exclude datadog-lambda-js and dd-trace. Skip this step if you don’t use serverless-webpack or you don’t have the includeModules option in your serverless.yml.

serverless.yml

custom:
  webpack:
    # You only need the following if you already have the includeModules option configured.
    includeModules:
      # ... your existing configuration for includeModules
      forceExclude:
        # @aws-sdk for the AWS SDK v3
        - @aws-sdk
        # aws-sdk for the AWS SDK v2
        - aws-sdk
        - datadog-lambda-js
        - dd-trace
    packagerOptions:
      scripts:
        # Optional, only needed when they are included as transitive dependencies 
        - rm -rf node_modules/datadog-lambda-js node_modules/dd-trace

To have more control around what dependencies are included, you could also include your webpack.config.js in your serverless-webpack configuration:

custom:
  webpack:
    forceExclude:
      # @aws-sdk for the AWS SDK v3
      - @aws-sdk
      # aws-sdk for the AWS SDK v2
      - aws-sdk
      - datadog-lambda-js
      - dd-trace
    webpackConfig: 'webpack.config.js'

esbuild

Follow the installation instructions for Node.js and ensure the Datadog Lambda layer for Node.js is added to your Lambda function.
Remove datadog-lambda-js and dd-trace from your package.json and the build process, since they are already available in the Lambda runtime provided by the Datadog Lambda layer.

Mark your dependencies as externals. This tells the bundler to exclude them from the output bundle; instead, they are packaged in node_modules.

esbuild.config.js

const esbuild = require('esbuild');

esbuild.build({
  // ... your existing esbuild configuration
  // Same effect as manually passing each dependency to `external`
  packages: 'external'
})

If you are using the serverless-esbuild plugin, you can externalize all dependencies with the esbuild-node-externals as an esbuild plugin. Automatically packs external modules under node_modules.

serverless.yml

custom:
  esbuild:
    exclude: 
      # @aws-sdk for the AWS SDK v3
      - @aws-sdk
      # aws-sdk for the AWS SDK v2
      - aws-sdk
      - datadog-lambda-js
      - dd-trace
    plugins: plugins.js
    # You can also set the specific dependencies to externalize instead of using `plugins`
    external: [...]

// plugins.js
const { nodeExternalsPlugin } = require('esbuild-node-externals')

module.exports = [nodeExternalsPlugin()]

AWS CDK

If you deploy Node.js Lambda functions using the NodeJsFunction construct, but aren’t using esbuild or Typescript, you can still use Datadog to observe your serverless applications.

Follow the installation instructions for Node.js and ensure the Datadog Lambda layer for Node.js is added to your Lambda function.
Remove datadog-lambda-js and dd-trace from your package.json and the build process, since they are already available in the Lambda runtime provided by the Datadog Lambda Layer.

Use the NodejsFunction construct in the CDK. Ensure you set the entry property to be the path to the file containing your Lambda function handler, the depsLockFilePath to the path to your lock file for the package manager you are using, and the bundling.commandHooks.beforeBundling to ensure all dependencies are installed.

lambdaFunction.ts

const nodeFunction = new NodejsFunction(this, "test", {
  runtime: Runtime.NODEJS_20_X,
  entry: './functions/consumer/index.js', // The Javascript file for your Lambda function handler
  handler: 'handler',
  depsLockFilePath: './package-lock.json', // The path to the lock file for your respective package manager (npm, yarn etc)
  bundling: {
    commandHooks: {
      beforeBundling(inputDir: string, outputDir: string) {
        return [
          `cd ${inputDir}`,
          'npm install', // Ensure all dependencies are installed before your Javascript file is zipped and deployed
        ]
      },
      beforeInstall() {
        return []
      },
      afterBundling() {
        return []
      }
    },
    externalModules: ['@aws-sdk/client-dynamodb'] // The AWS SDK is included as part of the Node.js Lambda runtime
  }
});

AWS CDK & esbuild

The NodeJsFunction construct in the AWS CDK uses esbuild. The default configuration is not compatible with Datadog’s tracing libraries. The CDK allows you to override the default configuration and provide a custom esbuild file to support bundling and the Datadog tracing libraries:

Follow the installation instructions for Node.js and ensure the Datadog Lambda layer for Node.js is added to your Lambda function.
Remove datadog-lambda-js and dd-trace from your package.json and the build process, since they are already available in the Lambda runtime provided by the Datadog Lambda Layer.

Create an esbuild file for each of your Lambda functions. A seperate esbuild file is required per Lambda function so that each entry point can be specified seperately. Notice the entryPoint and outfile properties. For example, if you had a second Lambda function in your project named producer, then the entry point would be ./functions/producer.ts and the outfile would be /out/producer/index.js

buildConsumer.js

const ddPlugin = require('dd-trace/esbuild')
const esbuild = require('esbuild')

esbuild.build({
  entryPoints: ['./functions/consumer.ts'],
  outfile: 'out/consumer/index.js',
  plugins: [ddPlugin],
  // Other esbuild configuration
  external: [
    // esbuild cannot bundle native modules
    '@datadog/native-metrics',

    // required if you use profiling
    '@datadog/pprof',

    // required if you use Datadog security features
    '@datadog/native-appsec',
    '@datadog/native-iast-taint-tracking',
    '@datadog/native-iast-rewriter',

    // required if you encounter graphql errors during the build step
    'graphql/language/visitor',
    'graphql/language/printer',
    'graphql/utilities',
    '@aws-sdk/client-sqs'

    // if you are using the package, instead of the layer
    'datadog-lambda-js'
  ]
}).catch((err) => {
  console.error(err)
  process.exit(1)
})

When defining your NodeJsFunction in the CDK, use the Code.fromCustomCommand function to specify the path to your custom esbuild file and an output folder. For each separate Lambda function, specify the individual esbuild file defined in step three. The output folder should match the folder of the outfile in your esbuild file.