api-traffic-analyzer Middleware Library

Overview

Track and analyze who’s using your API, how often, and from where.

api-traffic-analyzer is a lightweight Express middleware + CLI tool that helps you:

• Monitor unique visitors by IP (with auto-assigned numeric IDs)
• Optionally identify users with persistent cookies
• Automatically log each request's timestamp, IP, user ID, method, and endpoint
• Store logs in a simple text format for later analysis
• Use a CLI tool to inspect API traffic and usage patterns

Features

• Easy to drop into any Express-based app
• In-memory IP-to-ID mapping for tracking sessions
• Cookie-based user fingerprinting (optional, configurable)
• CLI support to analyze usage per endpoint, per user, per IP

How It Works

• When a request hits your Express server and passes through the logAnalyzer middleware:
  • The client’s IP is extracted.
  • If the IP is new, it is assigned a new unique numeric ID (0, 1, 2, ...).
  • Request metadata including timestamp, IP, IP ID, user ID (from request header), HTTP method, and endpoint are logged to a file (logs/users.log by default).
• The library maintains an in-memory mapping of IPs to their assigned IDs while the server is running.
• Logs can be later analyzed by your companion CLI tool or other analysis utilities.

Installation

npm install api-traffic-analyzer
npm install express          # Peer dependency, if not already installed
npm install --save-dev @types/express

Usage

1 - Import and apply the middleware in your index.js file in your Express.js app or router:

import express from 'express';
import { logAnalyzer } from 'api-traffic-analyzer';

const app = express();

app.use(logAnalyzer);  // Logs all requests on every route

app.get('/api/products', (req, res) => {
  res.json({ message: 'Products list' });
});

app.listen(3000, () => {
  console.log('Server running on http://localhost:3000');
});

Or apply selectively on specific routes:

import express from 'express';
import { logAnalyzer } from 'api-traffic-analyzer';

router.get('/events', logAnalyzer, (req, res) => {
  res.send('Events data');
});

2 - Add a user-id header in requests to track users. If user-id is missing, it defaults to "unknown" in logs.

The middleware looks for user-id in request headers:

GET /api/products HTTP/1.1
Host: example.com
user-id: 1001

3 - Logs are saved at logs/users.log

Example log line:

2025-07-06T12:00:00Z ip=192.168.1.2 ip_id=0 user_id=[cookie_or_header_user_id] GET /api/login

4 - Add analyze into your scripts in the folder package.json to be able to run npm run analyze and see the logs details.

"scripts": {
    "analyze": "node ./node_modules/api-traffic-analyzer/dist/cli.js logs/users.log",
  }

Run npm run analyze and make requests in your application or in the endpoints you added it. The output should be something like:

Total unique users: 1

📍 Endpoints accessed:
- /api/login → 1 user(s): [1001]

Users by IP:
- 192.168.1.2 → 1 user(s): [1001]

🍪 Optional: Cookie-based user tracking

If your API doesn’t already provide a user-id in the request headers (such as authenticated sessions or tokens), the api-traffic-analyzer can automatically generate and assign a unique user ID via cookies.

This allows you to identify unique users across multiple requests even without authentication.

Why use cookies?

Without a user ID in the request header, tracking how many unique users access your API would be based solely on IP addresses—which can change or be shared. To improve accuracy, the middleware sets a persistent cookie (api-traffic-analyzer_uid) with a unique UUID for each client.

Setup Steps

1 - Install cookie-parser:

npm install cookie-parser

2 - Apply it before logAnalyzer in your Express app:

import express from 'express';
import cookieParser from 'cookie-parser';
import { logAnalyzer } from 'api-traffic-analyzer';

app.use(cookieParser());   // 👈 Required for cookie-based tracking
app.use(logAnalyzer);      // Now supports automatic user ID via cookies

app.listen(3000, () => {
  console.log('Server running on http://localhost:3000');
});

About the Cookie

• Name: api-traffic-analyzer_uid
• Type: httpOnly (not accessible from client-side JavaScript)
• Duration: 1 year
• Purpose: Identify unique users anonymously in your log file

Example Log Entry With Cookie

2025-07-06T21:03:55.560Z ip=192.168.1.2 ip_id=0 user_id=3c80a32b-021c-4aa3-a867-22fc3a90e924 GET /api-docs/

If your app already sets a user-id in headers, this cookie-based fallback will not override it—it’s completely optional.