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Marko Djakovic for AWS Community Builders

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Deploy a NestJS API to AWS Lambda with Serverless Framework

Have you ever wondered how easy it can be to deploy and host an API? Scalable, stable, a piece of cake to deploy and costs almost nothing. The goal of this article is to demonstrate just that. We will develop a simple API which will be deployed to AWS cloud as a single Lambda function behind an API Gateway - a so-called Mono-Lambda. Whether Lambda "should" be used in that way is a different topic which I'd gladly discuss over beer. πŸ™‚πŸΊ

What to expect from this article?

We will just scratch the surface of NestJS framework and its neat development experience. Once we wire it with Serverless Framework, we'll learn how quickly our API can see the light of day, going from localhost to AWS cloud in just a few steps. To demonstrate this, we will create an API for managing a database of songs - Songs API, and we'll pretend it's not useless.

Requirements

Songs API will expose endpoints for listing all songs in the database, fetching a single song details, adding and removing songs. Given the requirements, the song model has properties id, name, artist, length in seconds, genre and album. API endpoints could look something like this:

  • GET songs
  • GET songs/:id
  • POST songs
  • DELETE songs/:id

Tech stack

  • NestJS - a powerful framework for creating sever-side applications
  • TypeORM - an ORM library for TypeScript, integrates nicely with Nest for database access
  • Serverless Framework - easy to use framework for developing and deploying serverless apps
  • Serverless Jetpack - a low-config plugin that packages our code to be deployed to AWS Lambda
  • Serverless Express - library that makes our "plain" NestJS API play nicely with Serverless
  • AWS managed services like Lambda, API Gateway and RDS

I hope it sounds fun and simple enough, so let's dig in.

Install Nest CLI and create a new project and module

npm i -g @nestjs/cli
nest new songs-api
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At this point the API is already set up - run it using npm run start and open localhost:3000 to see the hello world response. This is made possible by the main.ts file that is generated in the project root:

import { NestFactory } from '@nestjs/core';
import { AppModule } from './app.module';

async function bootstrap() {
  const app = await NestFactory.create(AppModule);
  await app.listen(3000);
}
bootstrap();
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Now we're going to create song module, which will contain the controller, service and entity definitions. Each of these can be created individually, but the Nest CLI provides a useful command to create the module and all the required files in it in one go. It comes in handy when creating REST APIs.

nest generate resource song
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Skeleton of the song module is generated. Next, we have to install dependencies for accessing the database. Since the API will run on top of a MySQL database, the following libraries should be added to the project:

npm install --save @nestjs/typeorm typeorm mysql2
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Implementation

Generating the module skeleton was convenient, but of course our business logic needs to be written. Perhaps we won't be needing all the generated DTOs, we might change or add some paths to the controller, and we need to implement our entity, of course.

Since we installed TypeORM dependency, let's use it to configure object-relational mapping for the Song entity according to the above specification:

import { Column, Entity, PrimaryGeneratedColumn } from 'typeorm';

@Entity()
export class Song {
  @PrimaryGeneratedColumn()
  id: number;

  @Column()
  name: string;

  @Column()
  artist: string;

  @Column()
  duration: number;

  @Column()
  genre: string;

  @Column()
  album: string;
}
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To make it work now we just need to add import to the module definition:

import { Module } from '@nestjs/common';
import { SongService } from './song.service';
import { SongController } from './song.controller';
import { TypeOrmModule } from '@nestjs/typeorm';
import { Song } from './entities/song.entity';

@Module({
  imports: [TypeOrmModule.forFeature([Song])],
  controllers: [SongController],
  providers: [SongService],
})
export class SongModule {
}
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Now, let's implement the service layer. SongService uses Repository provided by TypeORM to access the database:

import { Injectable } from '@nestjs/common';
import { InjectRepository } from '@nestjs/typeorm';
import { Repository } from 'typeorm';
import { Song } from './entities/song.entity';

@Injectable()
export class SongService {
  constructor(
    @InjectRepository(Song) private songRepository: Repository<Song>,
  ) {
  }

  async create(song: Song): Promise<Song> {
    return await this.songRepository.save(song);
  }

  async findAll(): Promise<Song[]> {
    return await this.songRepository.find();
  }

  async findOne(id: number): Promise<Song> {
    return await this.songRepository.findOne({ id });
  }

  async remove(id: number): Promise<void> {
    await this.songRepository.delete(id);
  }
}
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For simplicity, I'll re-use the entity as a DTO, so we can remove the whole dto folder that was generated. Then our controller and service will be rewritten to look something like this:

import { Body, Controller, Delete, Get, Param, ParseIntPipe, Post } from '@nestjs/common';
import { SongService } from './song.service';
import { Song } from './entities/song.entity';

@Controller('songs')
export class SongController {
  constructor(private readonly songService: SongService) {
  }

  @Post()
  async create(@Body() song: Song): Promise<Song> {
    return await this.songService.create(song);
  }

  @Get()
  async findAll(): Promise<Song[]> {
    return await this.songService.findAll();
  }

  @Get(':id')
  async findOne(@Param('id', ParseIntPipe) id: number): Promise<Song> {
    return await this.songService.findOne(id);
  }

  @Delete(':id')
  async remove(@Param('id', ParseIntPipe) id: number): Promise<void> {
    await this.songService.remove(id);
  }
}
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As a general rule, it's always better to de-couple DTO and entity classes and have some sort of object mapper.

Database

Database is mentioned quite a few times, but where is it? πŸ€”

Firstly, let's test our code against a local MySQL database. Once you connect to local server, execute the following init script:

CREATE DATABASE `songsapi`;

USE `songsapi`;

CREATE TABLE `song`
(
    `id`       int(11)      NOT NULL AUTO_INCREMENT,
    `name`     varchar(200) NOT NULL,
    `artist`   varchar(200) NOT NULL,
    `duration` int(11)      DEFAULT NULL,
    `genre`    varchar(45)  DEFAULT NULL,
    `album`    varchar(200) DEFAULT NULL,
    PRIMARY KEY (`id`)
) ENGINE = InnoDB
  DEFAULT CHARSET = utf8;
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After that make sure the API can connect to it by adding the following configuration to app.module.ts:

import { Module } from '@nestjs/common';
import { AppController } from './app.controller';
import { AppService } from './app.service';
import { TypeOrmModule } from '@nestjs/typeorm';
import { SongModule } from './song/song.module';

@Module({
  imports: [
    TypeOrmModule.forRoot({
      type: 'mysql',
      host: 'localhost',
      port: 3306,
      username: 'root',
      password: 'xxx',
      database: 'songsapi',
      autoLoadEntities: true,
    }),
    SongModule,
  ],
  controllers: [AppController],
  providers: [AppService],
})
export class AppModule {
}
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Feel free to hardcode the values above to those corresponding to your local database configuration.

Run it πŸš€

Type npm run start in the terminal and in a few seconds it should be up and running. Test it by sending some requests:

curl -X POST 'localhost:3000/songs' \
--header 'Content-Type: application/json' \
--data-raw '{
    "name": "In corpore sano",
    "artist": "Konstrakta",
    "duration": 182,
    "album": "In corpore sano",
    "genre": "pop"
}'
# Response:
# {"name":"In corpore sano","artist":"Konstrakta","duration":182,"album":"In corpore sano","genre":"pop","id":1}

# Get a single song by id
curl 'localhost:3000/songs/1'
# Response:
# {"name":"In corpore sano","artist":"Konstrakta","duration":182,"album":"In corpore sano","genre":"pop","id":1}
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It works! Now that we've tested our API locally, it's time to deploy it to the cloud and make it available to the world!

Moving to the cloud πŸŒ₯

NOTE 1: It is assumed that you already have an AWS account, so creating one will not be covered.

NOTE 2: Make sure you have enough privileges to follow the steps. In case of IAM user, the shortcut is to have arn:aws:iam::aws:policy/AdministratorAccess managed policy attached.

Configure AWS account credentials

Add a profile to your AWS credentials file (usually ~/.aws/credentials):

...
[profile-name]
region=your_region
aws_access_key_id=xxx
aws_secret_access_key=yyy
aws_session_token=... (if applicable)
...
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After that an environment variable should be set to activate the profile:

export AWS_PROFILE=profile-name
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You should be ready to interact with your AWS cloud, feel free to quickly test if it's setup correctly by listing all S3 buckets for example:

aws s3 ls

Spin up a free-tier RDS database

So far we have successfully tested the API with local MySQL database, but now we need one on AWS. It can be done manually through the AWS Console, or you can execute the CloudFormation template provided here.

*WARNING: Please be informed about the pricing and free-tier eligibility of your account. All new AWS customers should get 1 year of free tier for certain services. Otherwise you might incur some costs as described in the official AWS RDS pricing guide -> https://aws.amazon.com/rds/mysql/pricing

AWSTemplateFormatVersion: '2010-09-09'

Resources:
  SongsDatabase:
    Type: AWS::RDS::DBInstance
    Properties:
      AllocatedStorage: 20
      DBInstanceClass: db.t3.micro
      DBInstanceIdentifier: songs-database
      PubliclyAccessible: true
      StorageType: gp2
      MasterUsername: xxx # change
      MasterUserPassword: yyy # change
      Engine: mysql
      EngineVersion: 8.0.28
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Save the file above as rds.yaml for example and run it using AWS CLI:

aws cloudformation deploy --stack-name songs-api-db --template-file rds.yaml
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In a few minutes the database will be ready.

Obtain the database URL either through AWS Console by navigating to RDS, or by listing exports of CloudFormation using the following command aws cloudformation list-exports. Connect to it and execute the database init script as it was done for the local instance.

Now that our database is running in the cloud, it's time to reconfigure our app to work with the RDS database instead of local one - so don't forget to update the relevant details like url, password and the rest in app.module.ts file. After that it's ready to be deployed, which is covered in the next ste.

Install and configure Serverless Framework

Install Serverless Framework CLI:

npm install -g serverless
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In the root of the project, we should create the serverless.yaml file which describes the deployment:

service: songs-api

frameworkVersion: '3'

plugins:
  - serverless-jetpack

provider:
  name: aws
  runtime: nodejs14.x
  region: eu-central-1 # or whatever your region is

functions:
  api:
    handler: dist/lambda.handler
    events:
      - http:
          method: any
          path: /{proxy+}
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With this configuration, the API Gateway will just proxy every request to the Lambda function and our NestJS app will handle it. The handler value is a file that contains the entry point for our app and will be explained in a minute.

Notice the serverless-jetpack plugin - it takes care of packaging our app very efficiently for Serverless. There are other plugins for this, but I've discovered this one recently and it's a lot faster than others I've used so far. Read more about it on its official github page.

Install it as a dev dependency using npm:

npm i -D serverless-jetpack
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Now there's one more step before we can deploy our API - Serverless Express library to make it work in Lambda environment and it concerns the function handler.

Serverless Express

Install serverless-express library that bootstraps Express based apps to work with Lambda:

npm i @vendia/serverless-express
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Then, in the source folder create a lambda.ts file that contains the Lambda handler function, which is the entry point, as referenced in the above serverless.yaml.

import { configure as serverlessExpress } from '@vendia/serverless-express';
import { NestFactory } from '@nestjs/core';
import { AppModule } from './app.module';

let cachedServer;

export const handler = async (event, context) => {
  if (!cachedServer) {
    const nestApp = await NestFactory.create(AppModule);
    await nestApp.init();
    cachedServer = serverlessExpress({ app: nestApp.getHttpAdapter().getInstance() });
  }

  return cachedServer(event, context);
}
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Build, deploy & test πŸš€

Finally, we are going to deploy our API to the cloud. It's fairly simple, first it should be built:

npm run build
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... and then deployed:

serverless deploy
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Shortly, you'll get an auto-generated url which you can use to hit the API so feel free to test it by adding, listing and removing songs. You can see logs and monitor how your app performs in the built-in dashboards on Lambda & CloudWatch services on AWS Management Console.

Clean-up

After you've played around a bit with your API, it's time to clean-up all the resources you created on your AWS cloud. If you followed the steps exactly, you'll have two CloudFormation stacks deployed - one for the database and the other for the Serverless deployment. You can either remove them manually via the Console or by running the following CLI commands:

serverless remove
aws cloudformation delete-stack --stack-name songs-api-db
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Conclusion & final thoughts

I hope you made it this far and that I didn't bore you too much. Even though the main focus was on Serverless deployment on AWS Lambda, this article covered a few things along the way like setting up a simple NestJS project with TypeORM and creating an RDS MySQL database instance on AWS via CloudFormation.

What would be great for this kind of API to scale better is configuring an RDS Proxy on top of the database. Also, adding user authentication by using AWS Cognito is something which would fit nicely into this setup. Very recently AWS announced Lambda function URL feature, which eliminates the need for API Gateway but has other trade-offs, which I plan to explore next.

There are definitely some security aspects worth discussing for this to become production-ready, but it is beyond the scope of this article.

Thanks for reading and if you have any questions or suggestions feel free to comment!


Edit: There is a follow-up post on this, check it out - AWS Lambda Cold Starts: The Case of a NestJS Mono-Lambda API πŸ™‚

Top comments (23)

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jordi_alhambra_0ff9e573b0 profile image
Jordi Alhambra

Thanks for this tutorial. Sadly after running sls deploy, when I go to the production URL ending with / song, I get a 500 error. In Cloudwatch the error is: Cannot find module './dist/lambda.js'". Any idea on how to fix it? Cheers

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thatkit profile image
Nikita

It might be because nest-cli.json config file only expects main.ts to get compiled to main.js. So, one should specifylambda.ts as well or instead write hanlder() function in main.ts.

    "telegram-bot": {
      "type": "application",
      "root": "apps/telegram-bot",
      "entryFile": "main", // change to lambda
      "sourceRoot": "apps/telegram-bot/src",
      "compilerOptions": {
        "tsConfigPath": "apps/telegram-bot/tsconfig.app.json"
      }
    },
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jordi_alhambra_0ff9e573b0 profile image
Jordi Alhambra • Edited

I tried both options, but both results were Cannot find module either ./dist/lambda.js or ./dist/main.js
For the first: I added the entryFile to my out-of-the-box best v.10.0.0 different looking nest-cli.json :

{
  "$schema": "https://json.schemastore.org/nest-cli",
  "collection": "@nestjs/schematics",
  "sourceRoot": "src",
 "entryFile": "lambda", // added as suggested
  "compilerOptions": {
    "deleteOutDir": true
  }
}
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For the second option, I added the handler to the main.ts

import { NestFactory } from '@nestjs/core';
import { AppModule } from './app.module';
import { configure as serverlessExpress } from '@vendia/serverless-express';

let cachedServer;
export const handler = async (event, context) => {
  if (!cachedServer) {
    const nestApp = await NestFactory.create(AppModule);
    await nestApp.init();
    cachedServer = serverlessExpress({
      app: nestApp.getHttpAdapter().getInstance(),
    });
  }

  return cachedServer(event, context);
};

async function bootstrap() {
  const app = await NestFactory.create(AppModule);
  await app.listen(3000);
}
bootstrap();

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and updated the serverless.yml from

functions:
  api:
    handler: dist/lambda.handler
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to

functions:
  api:
    handler: dist/main.handler
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my tsconfig.json in case is relevant is:

{
  "compilerOptions": {
    "module": "commonjs",
    "moduleResolution": "node",
    "allowJs": true,
    "declaration": true,
    "removeComments": true,
    "emitDecoratorMetadata": true,
    "experimentalDecorators": true,
    "allowSyntheticDefaultImports": true,
    "target": "ES2021",
    "sourceMap": true,
    "outDir": "./dist",
    "incremental": true,
    "skipLibCheck": true,
    "strictNullChecks": false,
    "noImplicitAny": false,
    "strictBindCallApply": false,
    "forceConsistentCasingInFileNames": false,
    "noFallthroughCasesInSwitch": false,
  }

}

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Thread Thread
 
thatkit profile image
Nikita

Thanks for the reply! I guess I have to try the guide my own to check the reason solid clear. 'll get back with an update!

Thread Thread
 
thatkit profile image
Nikita

I'm back! :)
I've tried the whole thing with my NestJS + serverless.yaml setup and everything works good enough. However, I'm using Yandex Serverless Functions instead of AWS Lambda, but I tend to think this part is irrelevant to the issue.

Here're some of the info:

  1. nest version 9.5.0
  2. serverless versions
Framework Core: 3.38.0 (local) 3.38.0 (global)
Plugin: 7.2.0
SDK: 4.5.1
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  1. serverless.yaml
service: jojob-test

useDotenv: true

plugins:
  - serverless-offline
  - '@yandex-cloud/serverless-plugin'

package:
  patterns:
    - '!**'
    - package.json
    - package-lock.json
    - dist/**
    - config/production.js

provider:
  name: yandex-cloud
  runtime: nodejs18
  httpApi:
    payload: '1.0'

  environment:
    TG_TOKEN: ${env:TG_TOKEN}

    HH_CLIENT_ID: ${env:HH_CLIENT_ID}
    HH_CLIENT_SECRET: ${env:HH_CLIENT_SECRET}

    YOO_KASSA_SHOP_ID_TEST: ${env:YOO_KASSA_SHOP_ID_TEST}
    YOO_KASSA_SHOP_ARTICLE_ID_TEST: ${env:YOO_KASSA_SHOP_ARTICLE_ID_TEST}
    YOO_KASSA_TOKEN_TEST: ${env:YOO_KASSA_TOKEN_TEST}

    OAUTH_BASE_URL: ${env:OAUTH_BASE_URL}

functions:
  main:
    handler: dist/apps/telegram-bot/main.handler
    memorySize: 512
    timeout: 30
    account: function-sa
    events:
      - http:
          method: post
          path: /${self:provider.environment.TG_TOKEN}

resources:
  trigger-sa:
    type: yc::ServiceAccount
    roles:
      - serverless.functions.invoker
  function-sa:
    type: yc::ServiceAccount
    roles:
      - editor
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A note here! In the package rule I'm making sure that the dist directory with my main.ts file is compiled and other files that I do need.

  1. webpack.telegram.config.js (yes, since I need one according to the official docs)
/* eslint-disable @typescript-eslint/no-var-requires */
const nodeExternals = require('webpack-node-externals');
const NodeConfigWebpack = require('node-config-webpack');

module.exports = (options, webpack) => {
  const lazyImports = [
    '@nestjs/microservices/microservices-module',
    '@nestjs/websockets/socket-module',
  ];

  return {
    ...options,
    externals: [
      nodeExternals({
        allowlist: ['config'],
      }),
    ],
    plugins: [
      ...options.plugins,
      new NodeConfigWebpack(),
      new webpack.IgnorePlugin({
        checkResource(resource) {
          if (lazyImports.includes(resource)) {
            try {
              require.resolve(resource);
            } catch (err) {
              return true;
            }
          }
          return false;
        },
      }),
    ],
    output: {
      ...options.output,
      libraryTarget: 'commonjs2',
    },
  };
};
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  1. nest-cli.json
{
  "$schema": "https://json.schemastore.org/nest-cli",
  "collection": "@nestjs/schematics",
  "sourceRoot": "apps/jojob-api/src",
  "compilerOptions": {
    "deleteOutDir": true,
    "webpack": true,
    "tsConfigPath": "apps/jojob-api/tsconfig.app.json"
  },
  "projects": {
    "telegram-bot": {
      "type": "application",
      "root": "apps/telegram-bot",
      "entryFile": "main",
      "sourceRoot": "apps/telegram-bot/src",
      "compilerOptions": {
        "tsConfigPath": "apps/telegram-bot/tsconfig.app.json"
      }
    }
  },
  "monorepo": true,
  "root": "apps/jojob-api"
}
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  1. And finally, main.ts
import { NestFactory } from '@nestjs/core';
import serverlessExpress from '@vendia/serverless-express';
import { Callback, Context, Handler } from 'aws-lambda';
import { TelegramBotModule } from './telegram-bot.module';

let server: Handler;

async function bootstrap(): Promise<Handler> {
  const app = await NestFactory.create(TelegramBotModule);
  await app.init();

  const expressApp = app.getHttpAdapter().getInstance();

  return serverlessExpress({ app: expressApp });
}

export const handler: Handler = async (
  event: any,
  context: Context,
  callback: Callback,
) => {
  server = server ?? (await bootstrap());

  return server(event, context, callback);
};

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Thread Thread
 
thatkit profile image
Nikita

I'm not entirely sure what the exact reason behind your issue, but I guess you could try to debug if the main.ts/lambda.ts is being compiled into main.js/lambda.js and, furthermore, being packaged by Serverless Framework (in a .zip archive). I hope my configs will be of some help

Thread Thread
 
jordi_alhambra_0ff9e573b0 profile image
Jordi Alhambra

Just by adding the package section to the serverless.yml, and changing the handler there to dist/src/main.handler. Make it work, except now it's complaining about not finding modules, so I need to install them one by one : tslib,uid, iterare .... and it does not sound good. What am I missing?

Thread Thread
 
thatkit profile image
Nikita

OK. Now I would say some files are not packaged at all. Could you check the packaged file system in AWS Lambda editor? It seems the package.json is missing

Thread Thread
 
jordi_alhambra_0ff9e573b0 profile image
Jordi Alhambra

The file is present in the zip I downloaded from the lambda console.

Thread Thread
 
thatkit profile image
Nikita

Could you please show the latest error you've got?

Thread Thread
 
jordi_alhambra_0ff9e573b0 profile image
Jordi Alhambra

ERROR Error: Cannot find module 'fast-safe-stringify'
Require stack:

  • /var/task/node_modules/@nestjs/core/injector/module-token-factory.js
  • /var/task/node_modules/@nestjs/core/injector/compiler.js
  • /var/task/node_modules/@nestjs/core/injector/container.js
  • /var/task/node_modules/@nestjs/core/injector/index.js
  • /var/task/node_modules/@nestjs/core/index.js
  • /var/task/dist/src/main.js
  • /var/task/s_api.js
  • /var/runtime/index.mjs at Module._resolveFilename (node:internal/modules/cjs/loader:1077:15) at _require.i.require (/var/task/serverless_sdk/index.js:9:73131) at require (node:internal/modules/cjs/helpers:119:18) at Object. (/var/task/node_modules/@nestjs/core/injector/module-token-factory.js:7:31) at Module._compile (node:internal/modules/cjs/loader:1256:14) at Module._extensions..js (node:internal/modules/cjs/loader:1310:10) at Module.load (node:internal/modules/cjs/loader:1119:32) at Module._load (node:internal/modules/cjs/loader:960:12) at Module.require (node:internal/modules/cjs/loader:1143:19) at _require.i.require (/var/task/serverless_sdk/index.js:9:73397) { code: 'MODULE_NOT_FOUND', requireStack: [ '/var/task/node_modules/@nestjs/core/injector/module-token-factory.js', '/var/task/node_modules/@nestjs/core/injector/compiler.js', '/var/task/node_modules/@nestjs/core/injector/container.js', '/var/task/node_modules/@nestjs/core/injector/index.js', '/var/task/node_modules/@nestjs/core/index.js', '/var/task/dist/src/main.js', '/var/task/s_api.js', '/var/runtime/index.mjs' ] }
Thread Thread
 
jordi_alhambra_0ff9e573b0 profile image
Jordi Alhambra

I have uploaded my code to: github.com/arcovoltaico/nextjs

Thread Thread
 
thatkit profile image
Nikita

I remember a similar error in my setup. I had a module that wasn't compatible in this serverless build shema. I would try to build a serverless function with a minimum number of dependencies to figure out is it a general issue for all of your dependencies or a particular one.

At least, this is what I did with my codename.

Thread Thread
 
thatkit profile image
Nikita

Thanks for the git link. I've checked some of the configs, so a few notes:

  1. The handler path in serverless.yml should be dist/main.handler, not dist/src/main.handler. It's the path your nest app compiles things to.
  2. You need to replace the code in main.ts with the code in lamda.ts, since you're running a cachedServer in lamda.ts
Thread Thread
 
jordi_alhambra_0ff9e573b0 profile image
Jordi Alhambra

I think that was not the case. I compared this project with a plain Severless one that also works after being deployed, and I realised that the node-modules folder did contain all the child dependencies because I used npm.
So the culprit is pnpm, and it happens to NOT install them. I'm still not understanding how it can work locally. The fix is instead of running npmp install, choose pnpm install --shamefully-hoist instead.
Maybe not ideal, but the only option I know so far.

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thatkit profile image
Nikita

I'm glad your issue got resolved! Although, I'm quite sure with point 2 mentioned just above.

p.s. You could also try to switch to the basic npm as an ubiquitous standard and swap it with pnpm when there is a need for some optimization.

Happy serverless coding anyway!

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imflamboyant profile image
Marko Djakovic

Interesting and detailed discussion, thanks for your comments! I'm glad that you managed to resolve it in the end! I wasn't able to pitch in unfortunately.

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anilsonix profile image
Anil Kumar Soni

Thanks, great article.
Earlier I was able to run and test nest-api locally by running npm run start:dev.
But running this cmd with serverless-express , its not running on locally with watch mode.

How can I do this , so that both npm run start:dev gives me local api to play around.

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imflamboyant profile image
Marko Djakovic

Hi, thanks for reading and for your comment! I believe you should be able to run it just as before, so npm run start:dev should work. The serverless-express wrapper is only ran when it's deployed via serverless.

To emulate Lambda locally serverless-offline plugin can be used, however I am not sure if it supports the watch mode equivalent.

In any case let me know if you find any specifics, or if I misunderstood your question.

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anilsonix profile image
Anil Kumar Soni

Thanks, I was following another tut also, got confused. In another tut it modify the main.ts rather than creating a new file lambda.ts.

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imflamboyant profile image
Marko Djakovic

Cool πŸ˜‰

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Anthony Trinh

Hi, thanks for the article!

I was just wondering if you've run into the issue where DTO decorators for class-transformer and class-validator work locally in testing, but do not work once deployed to AWS ApiGateway/Lambda? Locally, the request will just be outright reject and it won't even attempt to process the request, when deployed it will attempt to process a request with a malformed DTO.

I am using the exact same tooling as you, and very similar set up.

Thanks!

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imflamboyant profile image
Marko Djakovic • Edited

Hi, thanks for the comment. If I understand your question correctly, I'd say that this is expected behavior. Lambda should proxy every request, it's up to your Nest app to handle validation responses, and just proxy them back to API Gateway.

If I misunderstood then feel free to provide more details about your issue and I'll try to pitch in. πŸ‘