LinkLibrarian

LinkLibrarian is a full-stack web app for registering users, logging in, and saving, editing, filtering, and deleting personal links.

Example comment of change.

Tech Stack

• Frontend: React + Vite
• Backend: Node.js + Express
• Database: MySQL
• Sessions: express-session + MySQL session store
• Hosting: Railway

Project Structure

project-root/
  backend/
  frontend/

• backend/ contains the Express server, session handling, and MySQL connection.
• frontend/ contains the Vite + React client.

Features

• User registration and login
• Session-based authentication
• Create, read, update, and delete links
• Tag filtering
• Local development support
• Production deployment on Railway

Local Development

1. Start the backend

Open a terminal in the backend/ folder and run:

npm install
npm start

The backend runs on:

http://localhost:3001

You can verify it with:

• http://localhost:3001/
• http://localhost:3001/api/test-db

2. Start the frontend

Open a second terminal in the frontend/ folder and run:

npm install
npm run dev

The frontend runs on:

http://localhost:5173

Frontend Environment Variables

This project uses Vite environment variables for switching between local and production API URLs. Vite exposes only variables prefixed with VITE_ to client-side code.

frontend/.env.local

VITE_API_BASE_URL=http://localhost:3001

This is used for local development.

frontend/.env.production

VITE_API_BASE_URL=https://linklibrarian-production.up.railway.app

This is used for production builds.

App.jsx usage

In frontend/src/App.jsx, the API base URL is read like this:

const API_BASE_URL = import.meta.env.VITE_API_BASE_URL || 'http://localhost:3001';

Railway Deployment

This app is deployed on Railway as three services:

• MySQL database
• Express backend
• Vite/React frontend

Railway frontend URL

https://linklibrarian-frontend-production.up.railway.app

Railway backend URL

https://linklibrarian-production.up.railway.app

Railway Frontend Service Setup

The frontend service is configured with:

• Root Directory: /frontend
• Public domain target port: 8080

Railway detects the frontend as a Vite static site, builds it into dist, and serves it with Caddy.

Railway Backend CORS Setup

The backend allows both local development and the Railway-hosted frontend by using an allowlist in server.js.

Example:

const allowedOrigins = [
  'http://localhost:5173',
  'https://linklibrarian-frontend-production.up.railway.app'
];

app.use(cors({
  origin: function (origin, callback) {
    if (!origin || allowedOrigins.includes(origin)) {
      callback(null, true);
    } else {
      callback(new Error('Not allowed by CORS'));
    }
  },
  credentials: true
}));

Important:

• Do not add a trailing slash to allowed origins.
• http://localhost:5173 works, but http://localhost:5173/ causes CORS errors.

Railway Frontend Variable

In the Railway frontend service, set:

VITE_API_BASE_URL=https://linklibrarian-production.up.railway.app

Because Vite frontend variables are baked into the build, changing this value requires a rebuild/redeploy.

Notes

• .env.local should stay local and should not usually be committed.
• VITE_ variables are not secret; they are visible in the frontend bundle.
• Database passwords, session secrets, and backend credentials must stay in backend or Railway service variables, not frontend env files.

Testing Checklist

Local

• Start local backend
• Start local frontend
• Open http://localhost:5173
• Confirm changes affect local MySQL only

Production

• Open https://linklibrarian-frontend-production.up.railway.app
• Register/login successfully
• Confirm CRUD actions affect Railway MySQL

Troubleshooting

NetworkError when attempting to fetch resource

Common causes:

• backend is not running locally
• frontend env variable points to the wrong API URL
• Railway frontend variable was changed but the app was not rebuilt
• CORS origin does not exactly match the frontend URL

CORS errors

Check:

• exact frontend origin
• no trailing slash in CORS allowlist
• credentials: true is enabled
• deployed frontend URL is included in allowedOrigins

Localhost frontend not working

Make sure both are running:

• backend at http://localhost:3001
• frontend at http://localhost:5173