api-latency-tracker

Automatically measures API performance for Express and Fastify

Install

npm install api-latency-tracker

Usage

Express

const express = require('express');
const { trackLatency, getStats, printReport } = require('api-latency-tracker');

const app = express();
app.use(trackLatency());

app.get('/users', (req, res) => res.json([{ id: 1, name: 'Alex' }]));
app.post('/login', (req, res) => res.json({ token: '...' }));

app.listen(3000);

// Later: print report
setInterval(printReport, 60000);  // every minute
// or: console.log(getStats());

Output:

API Latency Report
──────────────────────────────────────────────────
GET /users
  last: 120ms  avg: 85ms  p50: 80ms  p95: 150ms  (n=100)
POST /login
  last: 350ms  avg: 320ms  p50: 300ms  p95: 450ms  (n=50)

Fastify

const fastify = require('fastify')();
const { trackLatencyFastify, getStats } = require('api-latency-tracker');

fastify.register(trackLatencyFastify());

Get stats programmatically

const stats = getStats();
// { 'GET /users': { last: 120, avg: 85, p50: 80, p95: 150, p99: 200, count: 100 } }

Callback on each request

app.use(trackLatency({
  onRequest: ({ method, path, ms }) => {
    if (ms > 500) console.warn(`Slow: ${method} ${path} - ${ms}ms`);
  },
}));

API

| Function | Description | |----------|-------------| | trackLatency(options) | Express middleware (alias for trackLatencyExpress) | | trackLatencyExpress(options) | Express middleware | | trackLatencyFastify(options) | Fastify plugin | | getStats() | Returns latency stats per route | | printReport() | Logs report to console | | reset() | Clears collected data |

License

MIT