Expose real-time engine vitals to Prometheus or Datadog via io.getMetrics().
const snapshot = io.getMetrics();
// {
// activeConnections: 1204,
// totalConnections: 45012,
// messagesReceived: 981240,
// messagesSent: 2450120,
// messageErrors: 2,
// queueOverflows: 0,
// droppedBytes: 0,
// adapterErrors: 0
// }