Active connections, throughput, and queue depth exposed to observability layer

Without exported metrics, you cannot answer the most basic operational questions: how many connections are active right now, is message throughput degrading, is the outbound queue backing up? Invisible failures — a Redis adapter that silently stops publishing, a connection leak growing at 10 sockets per hour — go undetected until they cause an outage. ISO 25010 reliability includes the ability to monitor system health; a real-time service with no observability is operationally blind.

Export at minimum three gauges — active connections, messages processed, and queue depth — to a Prometheus-compatible endpoint or your existing observability backend.

import promClient from 'prom-client';

const activeConns = new promClient.Gauge({
  name: 'ws_active_connections',
  help: 'Live WebSocket connections',
});
const msgTotal = new promClient.Counter({
  name: 'ws_messages_total',
  help: 'Messages processed since startup',
});

io.on('connection', (socket) => {
  activeConns.inc();
  socket.on('disconnect', () => activeConns.dec());
  socket.on('send_message', () => msgTotal.inc());
});

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

Scrape /metrics from Prometheus or forward to Datadog/CloudWatch. Add an alert on ws_active_connections exceeding your tested ceiling.