Installation

System Requirements

Before installing the Price Tracker Bot, ensure your system meets these requirements:

Node.js

Version 16.0.0 or higherRequired for running the bot server and dependencies

npm

Version 7.0.0 or higherPackage manager (installed with Node.js)

Disk Space

~150 MB freeFor dependencies and Chromium browser

Operating System

Linux, macOS, or WindowsPlaywright supports all major platforms

Check Your Environment

Verify Node.js and npm are installed:

node --version
# Should output: v16.0.0 or higher

npm --version
# Should output: 7.0.0 or higher

If Node.js is not installed, download it from nodejs.org. The LTS version is recommended.

Installation Steps

Clone the Repository

Download the bot source code:

git clone https://github.com/your-username/price-tracker-bot.git
cd price-tracker-bot

If you don’t have Git installed, download the ZIP file from GitHub and extract it.

Install Dependencies

Install all required npm packages:

npm install

This command installs the following dependencies from package.json:

package.json

{
  "dependencies": {
    "axios": "^1.11.0",
    "dotenv": "^17.2.2",
    "node-cron": "^4.2.1",
    "node-fetch": "^3.3.2",
    "node-telegram-bot-api": "^0.66.0",
    "playwright": "^1.55.0"
  }
}

What Gets Installed

PackagePurposeSizenode-telegram-bot-apiTelegram Bot API client~2 MBplaywrightBrowser automation for web scraping~100 MBnode-cronScheduled price checks<1 MBdotenvEnvironment variable management<1 MBaxiosHTTP client~1 MBnode-fetchFetch API for Node.js<1 MB

Playwright will automatically download a Chromium browser (~100MB) during installation. This is required for scraping Amazon product pages.

Install Playwright Browsers

If Playwright didn’t auto-install browsers, run:

npx playwright install chromium

This downloads the Chromium browser that Playwright uses for scraping.

For production servers, you may need additional system dependencies:

Ubuntu/Debian

sudo npx playwright install-deps chromium

Fedora/CentOS

sudo npx playwright install-deps chromium

Create Environment Configuration

Create a .env file in the project root:

touch .env

Add your Telegram bot token:

TELEGRAM_TOKEN=your_telegram_bot_token_here

Getting Your Telegram Bot Token

Open Telegram and search for @BotFather
Send /newbot to create a new bot
Choose a name (e.g., “My Price Tracker”)
Choose a username (e.g., “my_price_tracker_bot”)
Copy the token BotFather provides

Keep your token secret! Anyone with access to this token can control your bot.Never commit .env to version control. It’s already in .gitignore.

Verify Installation

Check that the main file exists and is readable:

ls -la index.mjs

You should see:

-rw-r--r-- 1 user user 21234 Mar 10 12:00 index.mjs

Start the Bot

Run the bot:

npm start

Expected output:

ℹ️ No existe prices.json — se creará al guardar.
✅ Datos cargados. Productos: 0, Chats: 0
🚀 Bot iniciado. Esperando comandos...

The bot runs with Node.js --watch flag, so it automatically restarts when you edit index.mjs.

Project Structure

Understanding the bot’s file structure:

price-tracker-bot/
├── index.mjs          # Main bot application (753 lines)
├── package.json       # Dependencies and scripts
├── package-lock.json  # Locked dependency versions
├── .env               # Environment variables (create this)
├── prices.json        # Product data (auto-generated)
├── .gitignore         # Git ignore rules
└── README.md          # Project documentation

Key Files

index.mjs - Main Application

The core bot logic written in ES modules:

Lines 1-50: Configuration, imports, and data loading
Lines 52-136: Scraping engine with multiple CSS selectors
Lines 138-250: Price checking and notification logic
Lines 252-333: Chart generation using Chart.js
Lines 335-702: Telegram command handlers
Lines 704-740: Cron jobs for automation

index.mjs (excerpt)

import TelegramBot from "node-telegram-bot-api";
import cron from "node-cron";
import dotenv from "dotenv";
import { chromium } from "playwright";

dotenv.config();

const TELEGRAM_TOKEN = process.env.TELEGRAM_TOKEN;
if (!TELEGRAM_TOKEN) {
  console.error("❌ TELEGRAM_TOKEN no definido en .env");
  process.exit(1);
}

const bot = new TelegramBot(TELEGRAM_TOKEN, { polling: true });

See index.mjs:1-17 for initialization code.

prices.json - Data Storage

Auto-generated JSON file storing:

Product information (title, URL, price)
Price history (up to 120 data points)
Registered chat IDs
Metadata (dates, lowest price)

{
  "products": {
    "https://www.amazon.com/dp/B08N5WRWNW": {
      "url": "https://www.amazon.com/dp/B08N5WRWNW",
      "title": "Example Product",
      "price": 79.99,
      "lowestPrice": 79.99,
      "imageUrl": "https://...",
      "addedDate": "2024-03-10T12:00:00.000Z",
      "lastChecked": "2024-03-10T14:00:00.000Z",
      "addedBy": 123456789,
      "history": [
        {"date": "2024-03-10T12:00:00.000Z", "price": 99.99},
        {"date": "2024-03-10T14:00:00.000Z", "price": 79.99}
      ]
    }
  },
  "chats": [123456789]
}

Managed by loadData() and saveData() functions in index.mjs:24-48.

.env - Environment Variables

Secure configuration file (not committed to Git):

# Required
TELEGRAM_TOKEN=123456789:ABCdefGhIjKlmNoPQRsTUVwxyZ

# Optional (for future features)
# AWS_ACCESS_KEY=...
# DATABASE_URL=...

Loaded via dotenv.config() in index.mjs:8.

Configuration Options

Customize bot behavior by editing index.mjs:

Price Check Frequency

Modify the cron schedule:

index.mjs:732-740

// Check prices every 2 hours (default)
cron.schedule("0 */2 * * *", async () => {
  await checkPrices();
});

// Change to every 6 hours:
cron.schedule("0 */6 * * *", async () => {
  await checkPrices();
});

Daily Summary Time

Change when daily summaries are sent:

index.mjs:719-730

// Daily summary at 20:00 (default)
cron.schedule("0 20 * * *", async () => {
  // Send summaries
});

// Change to 9:00 AM:
cron.schedule("0 9 * * *", async () => {
  // Send summaries
});

Price History Limit

Adjust how many price points to store:

index.mjs:69

// Default: 120 price points
const HISTORY_LIMIT = 120;

// Increase to 240:
const HISTORY_LIMIT = 240;

Larger history limits increase prices.json file size. 120 points covers ~10 days of hourly checks.

Running in Production

Using PM2 Process Manager

For production deployments, use PM2 to keep the bot running:

# Install PM2 globally
npm install -g pm2

# Start the bot with PM2
pm2 start index.mjs --name price-tracker-bot

# View logs
pm2 logs price-tracker-bot

# Auto-restart on system reboot
pm2 startup
pm2 save

Using Docker

Create a Dockerfile:

Dockerfile

FROM node:18-slim

WORKDIR /app

# Install Playwright dependencies
RUN apt-get update && apt-get install -y \
    libnss3 \
    libatk-bridge2.0-0 \
    libdrm2 \
    libxkbcommon0 \
    libgbm1 \
    libasound2 \
    && rm -rf /var/lib/apt/lists/*

# Copy package files
COPY package*.json ./

# Install dependencies
RUN npm ci --only=production

# Install Playwright browsers
RUN npx playwright install chromium

# Copy application code
COPY index.mjs .

# Run the bot
CMD ["node", "index.mjs"]

Build and run:

# Build image
docker build -t price-tracker-bot .

# Run container
docker run -d \
  --name price-tracker \
  --env-file .env \
  -v $(pwd)/prices.json:/app/prices.json \
  price-tracker-bot

Using systemd (Linux)

Create a service file:

/etc/systemd/system/price-tracker-bot.service

[Unit]
Description=Price Tracker Bot
After=network.target

[Service]
Type=simple
User=your-user
WorkingDirectory=/path/to/price-tracker-bot
Environment="NODE_ENV=production"
ExecStart=/usr/bin/node index.mjs
Restart=always
RestartSec=10

[Install]
WantedBy=multi-user.target

Enable and start:

sudo systemctl enable price-tracker-bot
sudo systemctl start price-tracker-bot
sudo systemctl status price-tracker-bot

Troubleshooting Installation

npm install fails

Symptoms: Errors during npm installSolutions:

Clear npm cache:

npm cache clean --force
rm -rf node_modules package-lock.json
npm install

Update npm:

npm install -g npm@latest

Check Node.js version:

node --version
# Upgrade to Node.js 16+ if needed

Playwright installation errors

Symptoms: Chromium download fails or browser not foundSolutions:

Manual browser install:

npx playwright install chromium

Install system dependencies (Linux):

Ubuntu/Debian

sudo npx playwright install-deps chromium

Check disk space:

df -h
# Ensure at least 150MB free

TELEGRAM_TOKEN error on startup

Symptoms: ❌ TELEGRAM_TOKEN no definido en .envSolutions:

Verify .env file exists:

ls -la .env

Check file contents:

cat .env
# Should show: TELEGRAM_TOKEN=123456...

Ensure no extra spaces:

# ✅ Correct
TELEGRAM_TOKEN=123456789:ABC...

# ❌ Wrong (space before token)
TELEGRAM_TOKEN= 123456789:ABC...

Restart the bot:

npm start

Bot starts but doesn't respond

Symptoms: Bot runs but doesn’t reply to commandsSolutions:

Check bot token is valid:
- Talk to @BotFather
- Send /mybots → select your bot → API Token
Verify bot is running:

ps aux | grep node

Check for errors in console output
Send /start to register your chat ID

Scraping fails on all products

Symptoms: All /add commands fail with scraping errorsSolutions:

Test browser install:

npx playwright install chromium

Check network connectivity:

curl -I https://www.amazon.com

Try with --no-sandbox (already default in code):

index.mjs:148

const browser = await chromium.launch({ 
  headless: true, 
  args: ["--no-sandbox", "--disable-dev-shm-usage"] 
});

Increase timeout (if network is slow):

index.mjs:75

await page.goto(url, { 
  waitUntil: "domcontentloaded", 
  timeout: 60000  // Increase this
});

Permission denied errors

Symptoms: Cannot write to prices.jsonSolutions:

Check file permissions:

ls -la prices.json

Fix permissions:

chmod 644 prices.json

Ensure directory is writable:

ls -ld .
chmod 755 .

Security Considerations

Important Security Notes:

Never commit .env file - Contains your bot token
Keep prices.json private - Contains user chat IDs
Use firewall rules - Restrict outbound connections if needed
Regular updates - Keep dependencies updated with npm update
Monitor logs - Watch for suspicious activity

Securing Your Token

# Set restrictive permissions on .env
chmod 600 .env

# Verify .env is in .gitignore
grep .env .gitignore

Updating Dependencies

Keep packages secure:

# Check for vulnerabilities
npm audit

# Fix vulnerabilities automatically
npm audit fix

# Update all packages
npm update

# Check for outdated packages
npm outdated

Performance Tuning

Memory Usage

The bot’s memory footprint:

Base: ~50 MB (Node.js + dependencies)
Per browser instance: ~100-150 MB
Peak: ~200 MB during price checks

Browser instances are created per price check cycle and closed immediately after. See index.mjs:148-217 for browser lifecycle management.

Optimizing Price Checks

// Reduce delay between products (faster, more load)
await new Promise((r) => setTimeout(r, 500));  // Instead of 900ms

// Increase delay (slower, less load)
await new Promise((r) => setTimeout(r, 2000));  // Instead of 900ms

See index.mjs:214 for the delay between product checks.

Next Steps

Quickstart Guide

Learn how to use the bot and track your first product

Source Code

Explore the code on GitHub

Getting Help

If you encounter issues:

Check the Troubleshooting section above
Review console output for error messages
Ensure all requirements are met
Open an issue on GitHub with:
- Your Node.js version (node --version)
- Error messages from console
- Steps to reproduce

For questions about Amazon’s terms of service regarding scraping, review their robots.txt and scraping policies. This bot is for educational purposes.

Getting Started

Features

Commands

Configuration

Technical Details

Support

System Requirements

Node.js

npm

Disk Space

Operating System

Check Your Environment

Installation Steps

Getting Your Telegram Bot Token

Project Structure

Key Files

Configuration Options

Price Check Frequency

Daily Summary Time

Price History Limit

Running in Production

Using PM2 Process Manager

Using Docker

Using systemd (Linux)

Troubleshooting Installation

Security Considerations

Securing Your Token

Updating Dependencies

Performance Tuning

Memory Usage

Optimizing Price Checks

Next Steps

Quickstart Guide

Source Code

Getting Help

Build docs developers (and LLMs) love

Getting Started

Features

Commands

Configuration

Technical Details

Support

​System Requirements

Node.js

npm

Disk Space

Operating System

​Check Your Environment

​Installation Steps

​Getting Your Telegram Bot Token

​Project Structure

​Key Files

​Configuration Options

​Price Check Frequency

​Daily Summary Time

​Price History Limit

​Running in Production

​Using PM2 Process Manager

​Using Docker

​Using systemd (Linux)

​Troubleshooting Installation

​Security Considerations

​Securing Your Token

​Updating Dependencies

​Performance Tuning

​Memory Usage

​Optimizing Price Checks

​Next Steps

Quickstart Guide

Source Code

​Getting Help

Build docs developers (and LLMs) love

System Requirements

Check Your Environment

Installation Steps

Getting Your Telegram Bot Token

Project Structure

Key Files

Configuration Options

Price Check Frequency

Daily Summary Time

Price History Limit

Running in Production

Using PM2 Process Manager

Using Docker

Using systemd (Linux)

Troubleshooting Installation

Security Considerations

Securing Your Token

Updating Dependencies

Performance Tuning

Memory Usage

Optimizing Price Checks

Next Steps

Getting Help