Getting mysql:"Too many connections" despite using createPool in NodeJs - mysql

Question

I am using Observables to display real-time data in Angular2+ application and the back-end is written in NodeJs that uses MySQL database. Since I am using Observables, I need tens of millions of connections of MySQL to keep the real-time work going.
But it is not possible to acquire so many connections. So I used pooling where a connection is created from the pool of connections. However, I fail to implement it. I still get the error:
Error: ER_CON_COUNT_ERROR: Too many connections"
How can I close my connections so that the connections are not outnumbered?
Front end code:
angular.component.ts
Observable.interval(10000).subscribe(x => {
this.viewData(Val);
// more functions
console.log(" Observable")
});
NodeJS code:
dashboard.service.js
function viewData(data) {
var sqlQuery = `
select * from TRANSACTION_PAYLOAD where INTERFACE_NAME = 'Highmark' AND (STATUS ='SUCCESS_RESPONSE')`
var deferred = Q.defer();
console.log("INSIDE NODE JS SERVICE");
var host = config.host;
var user = config.user;
var password = config.password;
var database = config.database;
var con = mysql.createPool({
host: host,
user: user,
password: password,
database: database
});
con.getConnection(function (err) {
console.log("Inside .getConnection ")
if (err) deferred.reject(err.name + ': ' + err.message);
con.query(sqlQuery,
function (err, result, fields) {
if (err) deferred.reject(err.name + ': ' + err.message);
console.log(result);
deferred.resolve(result);
});
});
return deferred.promise;
con.close();
}

Answer 1

you are creating mysql pool for every request. You supposed to have single connection pool.
connection pool manages connections made to mysql server automatically.
you need to take out connection pool initialization out of your function.
take the connection pull out
const mysqlConOptions = {
host: host,
user: user,
password: password,
database: database
};
var conPool = mysql.createPool(mysqlConOptions);
inside your function,
conn = await conPool.getConnection();