[Feature/Question]: Dynamic reconnectPeriod (read Backoff strategy)

[olso-nordsec]

Hi,

I wanted to get your opinion on this. It seems there is no official approach to have dynamic reconnectPeriod.

But it is possible to reuse the same concept as laid out in https://github.com/mqttjs/MQTT.js#refresh-authentication-options--signed-urls-with-transformwsurl-websocket-only via transformWsUrl

const transformWsUrl = (url, options, client) => {
  // dynamic reconnectPeriod example
  client.options.reconnectPeriod = this.backoff.current().delay;

  client.options.username = `token=${this.get_current_auth_token()}`;
  client.options.clientId = `${this.get_updated_clientId()}`;

  return `${this.get_signed_cloud_url(url)}`;
}

const connection = await mqtt.connectAsync(<wss url>, {
  ...,
  transformWsUrl: transformUrl,
});

// somewhere in code on events `connect|reconnect|close|disconnect|offline|error|end`
this.backoff.increase();
this.backoff.decrease();

---

On which of these lifecycle events should/would you increase+decrease reconnectPeriod?

When I've tried playing with events, it seems sometimes I'm getting multiple events firings of same type.

This makes it difficult to distinguish which event is actionable for increase/decrease.

[robertsLando]

I like the idea, anyway I think this should be fixed before: #419