Can not import modules from Lambda Layers with Serverless framework and TypeScript - node.js

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!

Answer 1

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