DNS Round Robin failover doesn't work with mqtt.js - node.js

Question

I have a NodeJS Application that uses mqtt.js to connect to an emqx cluster.
The MQTT cluster contains of 2 nodes which I try to provide failover for using DNS Round Robin. So I have 1 A-Record (let's say mqtt.example.com) which points to 2 IPs (IP1 and IP2). When both nodes are online also my NodeJS application connects fine and subscribes to the selected topics.
Now on the MQTT nodes I can see what node the application is connected to. When I now stop the node that the application is connected to I expect that it would (sooner or later) fail over to the second active node.
I tested also with Loraserver (Which connected to MQTT) as well as the Node Red implementation of MQTT and both immediately connect to the active node when I stop the node they're connected to.
However my NodeJS application with mqtt.js keeps trying to connect to the node which I just stopped and doesn't try to connect to the active one.
Scenario explanation:
I have 2 Active nodes, IP1 and IP2
I connect Loraserver, Node Red and NodeJS to mqtt.example.com
All 3 applications connect to IP1
I stop IP1 node by shutting down the emqx process
Loraserver and Node Red will immediately connect to IP2 automatically
NodeJS with mqtt.js however keeps showing me error message
Error: connect ECONNREFUSED
with IP1 and doesn't fail over to IP2 (Kept it running for about 20 minutes and nothing happened. DNS lease time is set to 5 minutes if that's of any relavance)
How can I achiever failover using DNS Round Robing for an application using mqtt.js?
Thanks for any help
EDIT: As requested, added the testing code:
const mqtt = require('mqtt');
const tls = require('tls');
const MQTTTOPIC = 'test/upload';
const BROKER_URL = 'tls://mqtt.example.com';
const BROKER_PORT = '8883';
const MQTTUSER = 'username';
const MQTTPASS = 'password';
var mqttoptions = {
clientId: MQTTUSER,
port: BROKER_PORT,
keepalive: 60,
username: MQTTUSER,
password: MQTTPASS
};
var client = mqtt.connect(BROKER_URL, mqttoptions);
client.on('connect', mqtt_connect);
client.on('reconnect', mqtt_reconnect);
client.on('error', mqtt_error);
client.on('message', mqtt_messsageReceived);
client.on('close', mqtt_close);
function mqtt_connect() {
console.log("Connecting MQTT");
client.subscribe(MQTTTOPIC, mqtt_subscribe);
}
function mqtt_subscribe(err, granted) {
console.log("Subscribed to " + MQTTTOPIC);
if (err) { console.error(err); }
}
function mqtt_reconnect(err) {
console.log("Reconnect MQTT");
if (err) { console.error(err); }
client = mqtt.connect(BROKER_URL, mqttoptions);
}
function mqtt_error(err) {
console.error("MQTT Error!");
if (err) { console.error(err); }
}
function after_publish() {
//do nothing
}
function mqtt_close() {
console.warn("Close MQTT");
}
function mqtt_messsageReceived(topic, message, packet) {
console.log("Message: " + message + " --- Received on Topic " + topic);
}
EDIT 2:
In case it matters, I'm running the code with pm2
EDIT 3:
Plus the complete log output:
17|LOCALTE | Connecting MQTT
17|LOCALTE | Subscribed to test/upload
17|LOCALTE | Close MQTT
17|LOCALTE | Reconnect MQTT
17|LOCALTE | Error: connect ECONNREFUSED IP1:8883
17|LOCALTE | at Object.exports._errnoException (util.js:1034:11)
17|LOCALTE | at exports._exceptionWithHostPort (util.js:1057:20)
17|LOCALTE | at TCPConnectWrap.afterConnect [as oncomplete] (net.js:1096:14)
17|LOCALTE | MQTT Error!
17|LOCALTE | { Error: connect ECONNREFUSED IP1:8883
17|LOCALTE | at Object.exports._errnoException (util.js:1034:11)
17|LOCALTE | at exports._exceptionWithHostPort (util.js:1057:20)
17|LOCALTE | at TCPConnectWrap.afterConnect [as oncomplete] (net.js:1096:14)
17|LOCALTE | code: 'ECONNREFUSED',
17|LOCALTE | errno: 'ECONNREFUSED',
17|LOCALTE | syscall: 'connect',
17|LOCALTE | address: 'IP1',
17|LOCALTE | port: 8883 }
17|LOCALTE | Close MQTT
17|LOCALTE | Reconnect MQTT
[...]

Answer 1

Firstly you should not be calling connect() in the on.('reconnect') callback. The library will handle all of this for you.
...
function mqtt_reconnect(err) {
console.log("Reconnect MQTT");
if (err) { console.error(err); }
}
...
If it still doesn't work once you've removed this, as a work around you can list a group of servers that the library will round robin on it's own.
var mqttoptions = {
clientId: MQTTUSER,
port: BROKER_PORT,
keepalive: 60,
username: MQTTUSER,
password: MQTTPASS
servers:[
{
protocol: 'mqtts',
host: 'ip-address-1',
port: 8883
},
{
protocol: 'mqtts',
host: 'ip-address-2',
port: 8883
}
]
}