Working on a Node Js and MQTT Project
In this project, a device initially subscribes to a topic or list of topics and starts receiving messages published for those specific topic(s). An admin from the dashboard then assigns that device another new topic. The client code is running on the device (subscriber) and the admin does not have access to restart it. How can the device dynamically update to the newly assigned topic without needing a restart? Is it necessary to restart the device in order to receive the updated list of assigned topics?
//subscriber.js
var mqtt = require('mqtt')
var client = mqtt.connect('mqtt://test.mosquitto.org')
const mysql = require('mysql');
const subName = 'iPhoneX';
var subscribed = [];
const connection = mysql.createConnection({
host: 'localhost',
user: 'root',
password: '',
database: 'mydb'
});
connection.connect((err) => {
if (err) throw err;
console.log('Connected!');
});
var qry = `SELECT topic_name from sub_table s where s.sub_name='${subName}'`;
// Query database for subscribed topics
connection.query(qry, (err,rows) => {
if(err) throw err;
rows.forEach( (row) => {
console.log(row.topic_name);
subscribed.push(row.topic_name);
});
});
// Subscribe to retrieved topics
client.on('connect', function () {
subscribed.forEach(element => {
client.subscribe(element);
});
})
// Upon message receipt, log details
client.on('message', function (topic, message) {
console.log(topic, '------>', message.toString());
})
Publisher Setup
The publisher simply adds the topic name and assigns the entry to the respective device in the table before publishing a message with the specified topic name.
Objective
I aim to enable my subscriber to reconnect/restart seamlessly in order to fetch all updated devices when a new entry is assigned to the subscriber. Currently, after adding a new topic, restarting the subscriber code resolves the issue, but I am looking for a solution that does not involve restarting the code every time.