watchtower-agent

Drop-in Express middleware that captures HTTP metrics and process stats, pushes to a central collector with Slack, Discord, and email alerting.

Built on prom-client. MIT licensed.

Install

npm install watchtower-agent

Quick start

import { watchtower } from 'watchtower-agent';

app.use(watchtower({
  serviceName: 'my-api',
  collector: 'http://localhost:9090',  // optional
}));

What it captures

• HTTP request duration (histogram, p50/p95/p99)
• HTTP requests total (by method, route, status code)
• Node.js default metrics: CPU, memory, event loop lag, GC

Expose metrics endpoint (optional)

import { register } from 'watchtower-agent';

app.get('/metrics', async (req, res) => {
  res.set('Content-Type', register.contentType);
  res.send(await register.metrics());
});

Configuration

| Option | Default | Description | |---|---|---| | serviceName | 'app' | Identifies this service in the collector | | collector | undefined | URL of watchtower-collector. If omitted, metrics are only exposed locally |

Architecture

Your app (watchtower middleware)
  └─ pushes Prometheus text every 15s
       └─ watchtower-collector
            ├─ evaluates alert rules every 30s
            ├─ fires Slack webhook
            ├─ fires Discord webhook
            └─ sends email via Resend

Pair with watchtower-collector

See watchtower-collector for the collector + alerting setup.

What this isn't

Not a replacement for Prometheus + Grafana in production. This is a focused agent + collector + alerting pipeline for teams that want observability without the setup overhead. For production scale, use OpenTelemetry.

License

MIT