デプロイ済の Layer 構成

  └─ nodejs/
      ├─ @layer/
      │     └─ util/
      │          ├─ index.js
      │          ├─ package.json
      │          └─ package-lock.json
      │
      ├─ node_modules/
      ├─ package.json
      └─ package-lock.json

デプロイ済の Layer 実装

index.js

module.exports = {
  sample: value => {
    return value;
  },
};

Layer（ARN）をアタッチした Lambda 定義

※ Layer（ARN）を SSM に格納しておいた場合

stack.ts

import * as cdk from '@aws-cdk/core';
import * as lambda from '@aws-cdk/aws-lambda';
import * as lambdaNodejs from '@aws-cdk/aws-lambda-nodejs'
import * as ssm from '@aws-cdk/aws-ssm';
export class AwsCdkTsStack extends cdk.Stack {
  constructor(scope: cdk.Construct, id: string, props?: cdk.StackProps) {
    super(scope, id, props);

    const utilLayerArnParamName = '/layer/utilLayerArn';
    const utilLayerArn = ssm.StringParameter.valueForStringParameter(this, utilLayerArnParamName);
    const utilLayer = lambda.LayerVersion.fromLayerVersionArn(this, 'utilLayer', utilLayerArn);

    new lambdaNodejs.NodejsFunction(this, 'api', {
      layers: [utilLayer],
      bundling: {
        externalModules: ['@layer/util']
      },
    })
  }
}

Layer を使用する Lambda 実装

stack.api.ts

import { Handler } from 'aws-lambda'
const util = require('@layer/util');

export const handler: Handler = async () => {

  const result = util.sample(100);
}