Can not import modules from Lambda Layers with Serverless framework and TypeScript

Question

I have several functions in my serverless app. Two of them are for REST endpoints and one is SQS handler. They all are using the same libraries. So, I want to move them to Lambda Layer and share across functions to reduce size.

I'm using Serverless framework 2.46, TypeScript 4.3 and NodeJS 14. I have the following project structure:

/
 - layers/
   - nodejs/
     - node_modules/
     - package.json
 - src/
   - handlers/ - here are my handlers 
   - etc...

I've configured TypeScript to import libraries from the layer folder like this import middy from '/opt/nodejs/@middy/core';. Here is my tsconfig

{
  "compilerOptions": {
    "preserveConstEnums": true,
    "strictNullChecks": true,
    "sourceMap": true,
    "allowJs": false,
    "target": "ES2020",
    "module": "CommonJS",
    "outDir": ".build",
    "moduleResolution": "node",
    "esModuleInterop": true,
    "resolveJsonModule": true,
    "experimentalDecorators": true,
    "emitDecoratorMetadata": true,
    "lib": [
      "ES6",
      "ES2019",
      "ES2020"
    ],
    "baseUrl": ".",
    "paths": {
      "/opt/nodejs/*": [
        "layers/nodejs/node_modules/*"
      ]
    }
  },
  "exclude": [
    "node_modules",
    "opt/nodejs/node_modules"
  ]
}

And have serverless config like this

service: my_serverless-app
frameworkVersion: '2'
useDotenv: true
variablesResolutionMode: 20210326
configValidationMode: error

custom:
  stage: ${opt:stage, self:provider.stage}
  dbHost:
    local: ${env:DB_HOST, ''}
    dev: ${ssm:DB_HOST_DEV}

  dbPort:
    local: ${env:DB_PORT, ''}
    dev: ${ssm:DB_PORT_DEV}

  dbUser:
    local: ${env:DB_USER, ''}
    dev: ${ssm:DB_USER_DEV}

  dbPassword:
    local: ${env:DB_PASSWORD, ''}
    dev: ${ssm:DB_PASSWORD_DEV}

  dbName:
    local: ${env:DB_NAME, ''}
    dev: ${ssm:DB_NAME_DEV}

provider:
  name: aws
  region: us-east-1
  stage: dev
  runtime: nodejs14.x
  lambdaHashingVersion: 20201221
  environment:
    NODE_PATH: "./:opt/nodejs/node_modules"
    DB_HOST: ${self:custom.dbHost.${self:custom.stage}}
    DB_PORT: ${self:custom.dbPort.${self:custom.stage}}
    DB_USER: ${self:custom.dbUser.${self:custom.stage}}
    DB_PASSWORD: ${self:custom.dbPassword.${self:custom.stage}}
    DB_NAME: ${self:custom.dbName.${self:custom.stage}}

plugins:
  - serverless-plugin-typescript
  - serverless-offline

functions:
  getLedgerRecords:
    handler: src/handlers/ledger.ledgerRecords
    events:
      - http:
          path: /ledger-records
          method: get
    layers:
      - { Ref: CommonLibsLambdaLayer }

  getLedgerRecord:
    handler: src/handlers/ledger.ledgerRecord
    events:
      - http:
          path: /ledger-records/{id}
          method: get
    layers:
      - { Ref: CommonLibsLambdaLayer }

layers:
  CommonLibs:
    path: layers/nodejs
    description: "Common dependencies"
    compatibleRuntimes:
      - nodejs14.x

When I run the app locally via command serverless offline --stage local I have no error, but when I execute an REST endpoint (or any other) I have the following error:

[offline] Loading handler... (D:\Projects\services\.build\src\handlers\ledger)
[offline] _____ HANDLER RESOLVED _____
offline: Failure: Cannot find module '/opt/nodejs/@middy/core'
Require stack:
- D:\Projects\services\.build\src\handlers\ledger.js
- D:\Projects\services\node_modules\serverless-offline\dist\lambda\handler-runner\in-process-runner\InProcessRunner.js
- D:\Projects\services\node_modules\serverless-offline\dist\lambda\handler-runner\in-process-runner\index.js
- D:\Projects\services\node_modules\serverless-offline\dist\lambda\handler-runner\HandlerRunner.js
- D:\Projects\services\node_modules\serverless-offline\dist\lambda\handler-runner\index.js
- D:\Projects\services\node_modules\serverless-offline\dist\lambda\LambdaFunction.js
- D:\Projects\services\node_modules\serverless-offline\dist\lambda\LambdaFunctionPool.js
- D:\Projects\services\node_modules\serverless-offline\dist\lambda\Lambda.js
- D:\Projects\services\node_modules\serverless-offline\dist\lambda\index.js
- D:\Projects\services\node_modules\serverless-offline\dist\ServerlessOffline.js
- D:\Projects\services\node_modules\serverless-offline\dist\index.js
- D:\Projects\services\node_modules\serverless-offline\dist\main.js
- D:\Projects\services\node_modules\serverless\lib\classes\PluginManager.js
- D:\Projects\services\node_modules\serverless\lib\Serverless.js
- D:\Projects\services\node_modules\serverless\scripts\serverless.js
- D:\Projects\services\node_modules\serverless\bin\serverless.js

Also, I have the same problem when I'm trying to deploy the app. What am I doing wrong? Please drop me a link for tutorial how to configure lambda layers properly. Thanks in advance!

oieduardorabelo oieduardorabelo · Accepted Answer · 2021-07-21T12:13:48

your layer configuration is correct from the Serverless Framework and TypeScript perspective.

the problem could be in the packing of the project itself (e.g. internal of serverless-plugin-typescript)

i would suggest trying another TypeScript plugin, like serverless-esbuild

using your tsconfig.json example and samples from serverless.yml. I created an example here:

https://github.com/oieduardorabelo/2021-07-21-serverless-typescript-layers

it is using esbuild for packing and transpile TypeScript to JavaScript and it is working as expected

Can not import modules from Lambda Layers with Serverless framework and TypeScript

1 Answers