CRUD API

Simple CRUD API with an in-memory database and a load balancer.

Stack:

• Node.js
• TypeScript
• ESLint /Prettier
• Jest / supertest
• nodemon / dotenv / cross-env

Usage

# Install dependencies
npm install

# Run in develpment
npm run start:dev

# Run in production
npm run start:prod

# Run in cluster mode
npm run start:multi

# Run tests
npm run test

# Run ESLint
npm run lint

Routes

GET      /api/users
POST     /api/users
GET      /api/users/:id
PUT      /api/users/:id
DELETE   /api/users/:id

User interface:

{
  id: string (uuid);
  username: string;  
  age: number;       
  hobbies: string[];  
}

Load balancer

This app supports horizontal scaling for application. It utilizes load balancer based on the Node.js Cluster API (Round-robin algorithm). For example: host machine has 4 cores, PORT is 4000. On run npm run start:multi it works following way

• On localhost:4000/api load balancer is listening for requests
• On localhost:4001/api, localhost:4002/api, localhost:4003/api, localhost:4004/api workers are listening for requests from load balancer
• When user sends request to localhost:4000/api, load balancer sends this request to localhost:4001/api, next user request is sent to localhost:4002/api and so on.
• After sending request to localhost:4004/api load balancer starts from the first worker again (sends request to localhost:4001/api)
• State of db should be consistent between different workers, for example:
  1. First POST request addressed to localhost:4001/api creates user
  2. Second GET request addressed to localhost:4002/api should return created user
  3. Third DELETE request addressed to localhost:4003/api deletes created user
  4. Fourth GET request addressed to localhost:4004/api should return 404 status code for created user