Website-Monitor

An uptime monitor for a list of sites you care about. The backend polls every URL on a fixed interval, records whether it answered, and the React dashboard shows the current state of each one.

How it works

The monitoring loop lives in back/src/utils/isAlive.ts and starts with the server:

startMonitoring()
   │
   ├─ initial sweep on boot
   └─ setInterval, every 5 minutes
         │
         └─ for every site in MongoDB (in parallel):
              GET url  (30s timeout)
                 │
                 ├─ 2xx / 3xx  → alive
                 └─ 4xx / 5xx / timeout / DNS failure → down
                       │
                       └─ write to DB **only when the status changed**

Two details worth calling out:

• Checks run in parallel (Promise.all), so one slow site doesn't delay the rest of the sweep.
• Writes happen only on transition. A site that stays up for a week produces zero database writes — the isAlive field is touched only when a site flips between up and down.

Structure

back/     Express + TypeScript API and the polling engine
  src/routes        REST routes
  src/controllers   request handling
  src/services      MongoDB access
  src/models        Mongoose schema (url, name, isAlive)
  src/utils/isAlive.ts   the monitoring loop
  src/middleware    async wrapper + central error handler

ui/       React + Vite + Tailwind dashboard
  src/pages/Dashboard.tsx     status overview
  src/pages/AllWebsites.tsx   full list, add and remove
  src/hooks                   data fetching

Stack

Backend — Node.js, Express, TypeScript, MongoDB (Mongoose), axios, Docker Frontend — React, Vite, TypeScript, Tailwind CSS, React Router, react-hot-toast

API

Method	Route	Description
GET	/websites	List all monitored sites with their current status
POST	/websites	Add a site ({ name, url })
PUT	/websites/:id	Update a site
DELETE	/websites/:id	Stop monitoring a site
GET	/isAlive	Health check for the monitor itself

Running it

Backend

cd back
npm install
cp .env.example .env      # then fill in the values below
npm run dev

.env:

PORT=3000
MONGO_URI=mongodb://localhost:27017/website-monitor

Frontend

cd ui
npm install
npm run dev               # http://localhost:5173

Docker — a Dockerfile for the backend lives in back/.

Current limits

Worth knowing before you rely on it:

• The interval is fixed at 5 minutes and hardcoded in isAlive.ts. It isn't configurable per site yet.
• No history is kept. Only the current isAlive value is stored, so there is no uptime percentage, no incident timeline and no "down since" timestamp.
• Alerting is a stub. Sites that fail a check are logged to the console; the hook where an email or webhook would go is marked in checkAllServers but not implemented.
• Liveness is HTTP status only. A site returning 200 with a broken page counts as alive — there is no content assertion or response-time threshold.