How to Monitor Your NATS Messaging System with Vigilmon

NATS is a high-performance, cloud-native messaging system used by teams building distributed systems, microservices, and event-driven architectures. Unlike heavier brokers, NATS is fast, lightweight, and designed for simplicity — but that simplicity can hide gaps in observability.

This guide shows you how to set up external uptime monitoring for NATS with Vigilmon.

Why Monitor NATS Externally?

NATS exposes a built-in HTTP monitoring endpoint at port 8222 by default. This gives you real-time stats. But internal metrics do not tell you whether your NATS server is reachable from the outside world.

External monitoring answers:

• Is the NATS server reachable over the network?
• Is the monitoring HTTP endpoint responding?

Step 1: Enable the NATS HTTP Monitoring Port

NATS ships with monitoring disabled by default. Enable it in your config:

port: 4222
http_port: 8222

Test the monitoring endpoint:

curl http://localhost:8222/varz

Step 2: Create a Health Endpoint

The built-in /varz endpoint is verbose. Expose a simple health route:

const { connect } = require('nats');
const http = require('http');

let isConnected = false;

async function main() {
  try {
    const nc = await connect({ servers: 'nats://localhost:4222' });
    isConnected = true;
  } catch (err) {
    isConnected = false;
  }

  http.createServer((req, res) => {
    if (req.url === '/health') {
      if (isConnected) {
        res.writeHead(200);
        res.end(JSON.stringify({ status: 'ok', nats: 'connected' }));
      } else {
        res.writeHead(503);
        res.end(JSON.stringify({ status: 'error', nats: 'disconnected' }));
      }
    }
  }).listen(3000);
}

main();

Step 3: Add to Vigilmon

1. Log in at vigilmon.online
2. Click + Add Monitor
3. Set the URL: https://your-service.example.com/health
4. Set check interval: 1 minute
5. Set expected status: 200

What to Monitor

What to Monitor	How
NATS server reachability	HTTP check on 8222/varz
Application NATS connection	Custom /health endpoint

NATS is fast and reliable — but your monitoring needs to be external to be meaningful. Set up your Vigilmon monitor once, and you'll know the instant NATS becomes unreachable.

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Vigilmon provides free uptime monitoring for NATS and any HTTP endpoint.