Serverless - AWS Node.js Typescript

This project is a modified version of a template that has been generated using the aws-nodejs-typescript template from the Serverless framework.

These modifications are:

• HTTP API: This project runs on AWS API Gateway HTTP API instead of the API Gateway REST API. The main goal of this is to save costs (see pricing)
  • If you would like to use the REST API, then simply go to src/<your-function-name>/index.ts and change httpApi to http
  • I highly recommend checking out the differences between HTTP APIs and REST APIs and choosing your API type based on the features that you need.
• Validation: Since tbe REST API has built-in validation, and HTTP API does not, this modified package compensates by including middy's validator middleware that validates JSON schemas using ajv.
• Response Serialization: Serialization of the HTTP response from a JavaScript object to a JSON is done using middy http-response-serializer middleware.
• Handling Error Messages: This package also uses middy http-error-handle to handle errors coming from the validation or the developer.

For detailed instructions, please refer to the documentation.

Installation/deployment instructions

Depending on your preferred package manager, follow the instructions below to deploy your project.

Requirements: NodeJS lts/fermium (v.14.15.0). If you're using nvm, run nvm use to ensure you're using the same Node version in local and in your lambda's runtime.

Using NPM

• Run npm i to install the project dependencies
• Run npx sls deploy to deploy this stack to AWS

Using Yarn

• Run yarn to install the project dependencies
• Run yarn sls deploy to deploy this stack to AWS

Test your service

This template contains a single lambda function triggered by an HTTP request made on the provisioned API Gateway HTTP API /hello route with POST method. The request body must be provided as application/json. The body structure is tested by a validator middlware against src/functions/hello/schema.ts JSON-Schema definition: it must contain the name property.

• requesting any other path than /hello with any other method than POST will result in API Gateway returning a 404 Not Found HTTP error code
• sending a POST request to /hello with a payload not containing a string property named name will result in API Gateway returning a 400 Bad Request HTTP error code
• sending a POST request to /hello with a payload containing a string property named name will result in API Gateway returning a 200 OK HTTP status code with a message saluting the provided name and the detailed event processed by the lambda.

⚠️ As is, this template, once deployed, opens a public endpoint within your AWS account resources. Anybody with the URL can actively execute the API Gateway endpoint and the corresponding lambda. You should protect this endpoint with the authentication method of your choice.

Locally

In order to test the hello function locally, run the following command:

• npx sls invoke local -f hello --path src/functions/hello/mock.json if you're using NPM
• yarn sls invoke local -f hello --path src/functions/hello/mock.json if you're using Yarn

Check the sls invoke local command documentation for more information.

Remotely

Copy and replace your url - found in Serverless deploy command output - and name parameter in the following curl command in your terminal or in Postman to test your newly deployed application.

curl --location --request POST 'https://myApiEndpoint/dev/hello' \
--header 'Content-Type: application/json' \
--data-raw '{
    "name": "Frederic"
}'

Template features

Project structure

The project code base is mainly located within the src folder. This folder is divided in:

• functions - containing code base and configuration for your lambda functions
• libs - containing shared code base between your lambdas

.
├── src
│   ├── functions               # Lambda configuration and source code folder
│   │   ├── hello
│   │   │   ├── handler.ts      # `Hello` lambda source code
│   │   │   ├── index.ts        # `Hello` lambda Serverless configuration
│   │   │   ├── mock.json       # `Hello` lambda input parameter, if any, for local invocation
│   │   │   └── schema.ts       # `Hello` lambda input event JSON-Schema
│   │   │
│   │   └── index.ts            # Import/export of all lambda configurations
│   │
│   └── libs                    # Lambda shared code
│       └── apiGateway.ts       # API Gateway specific helpers
│       └── handlerResolver.ts  # Sharable library for resolving lambda handlers
│       └── lambda.ts           # Lambda middleware
│
├── package.json
├── serverless.ts               # Serverless service file
├── tsconfig.json               # Typescript compiler configuration
├── tsconfig.paths.json         # Typescript paths
└── webpack.config.js           # Webpack configuration

3rd party libraries

• json-schema-to-ts - uses JSON-Schema definitions used by API Gateway for HTTP request validation to statically generate TypeScript types in your Lambda's handler code base
• middy - middleware engine for Node.Js Lambda.
  • http-json-body-parser to convert API Gateway event.body property, originally passed as a stringified JSON, to its corresponding parsed object.
  • validator to validate API Gateway events
  • http-error-handle to handle errors coming from the validation or the developer.
• @serverless/typescript - provides up-to-date TypeScript definitions for your serverless.ts service file

Advanced usage

Any tsconfig.json can be used, but if you do, set the environment variable TS_NODE_CONFIG for building the application, eg TS_NODE_CONFIG=./tsconfig.app.json npx serverless webpack