lambda-starter

A starting pattern for AWS lambda in Typescript

Requirements

• node v16.17.1 (Note if still using node 14 please checkout tag 1.0.0 and consider upgrading your runtime)
• SAM CLI
• npm 8+

Prerequisites

• Create a .env

  cp .env.example .env

Build

• npm i
• npm run build:dev

Watch

To watch for changes and automatically trigger a new build:

• npm run watch:dev

Run Lambdas Locally

• Build the files first
• npm run start:dev
• To ensure that the lambdas have been successfully served, run the following command in a separate terminal:
  • curl --request GET http://localhost:3000/?message=hello%20world
  • the response should be: {"queryParams": {"message": "hello world"}}
• To run CloudWatch Event lambdas: npm run invoke -- CloudWatchEventLambdaFunction

Debug Lambdas Locally (VS Code only)

• Run lambdas in debug mode: npm run start:dev -- -d 5858
• Add a breakpoint to the lambda being tested (src/handler/get.ts)
• Run the debug config from VS Code that corresponds to lambda being tested (GetLambdaFunction)
• Send an HTTP request to the lambda's URI (curl --request GET http://localhost:3000/?message=hello%20world)
• To debug CloudWatch Event lambdas: npm run invoke -- CWEventLambdaFunction -d 5858

Tests

• The Jest framework is used to run tests and collect code coverage
• To run the tests, run the following command within the root directory of the project: npm test
• Coverage results will be displayed on terminal and stored in the coverage directory
  • The coverage requirements can be set in jest.config.js

Logging Logging is handled by https://github.com/winstonjs/winston. A pre-configured logger is available, and can be used like so:

import logger from "../utils/logger";

logger.info('Hello world');
logger.error('Hello world');
logger.warn('Hello world');

Tip: It's usually a good idea to attach the requestId and any X-Correlation-Id to the logger object's meta data so every log message will contain these useful bits of information.

  const event: APIGatewayProxyEvent = currentInvoke.event as APIGatewayProxyEvent;
  const correlationId: string = event.headers['X-Correlation-Id'] || (currentInvoke.context as Context).awsRequestId;

  const { requestId } = event.requestContext;

  req.app.locals.correlationId = correlationId;
  req.app.locals.requestId = requestId;

  Logger.defaultMeta = { requestId, correlationId };