NodeJS: Heroku ClearDB not closing connections - mysql

Question

I deployed a NodeJS API on Heroku and tried to connect it to a MySQL DB, so I created a connectionPool for handling connections on a ClearDB ignite account (free), which allows a maximum of 10 connections.
Every time I execute a query to the database it just adds a new connection to the stack until it reaches 10 connections and the app crashes.
My code is as follows:
connectionFactory:
var mysql = require('mysql');
function createDBConnection() {
var conn = mysql.createPool({
host: 'xxx',
user: 'xxx',
password: 'xxx',
database: 'xxx'
});
return conn;
}
module.exports = function() {
return createDBConnection;
}
And here's my select query:
function Dao(connection) {
this._connection = connection;
}
Dao.prototype.findAll = function (callback) {
this._connection.query('SELECT * FROM table',
function(errors, results) {
callback(errors,results);
});
};
module.exports = function() {
return Dao;
}
Finally here's the route I use to call it:
app.get('/products', function (req,res) {
var connection = app.persistence.connectionFactory();
var dao = new app.persistence.Dao(connection);
dao.findAll(function (err, result) {
res.format({
json: function () {
res.json(result);
}
});
});
});
I tried changing createPool() to createConnection() and then calling .end()/.destroy() function right after each query but it doesn't work at all.
Any hints?

Answer 1

In order to close a connection / return a connection to the pool use : connection.release()
var mysql = require('mysql');
var pool = mysql.createPool(...);
pool.getConnection(function(err, connection) {
// Use the connection
connection.query('SELECT something FROM sometable', function (error, results, fields) {
// And done with the connection.
connection.release();
// Handle error after the release.
if (error) throw error;
// Don't use the connection here, it has been returned to the pool.
});
});
mysql : Pooling connections Documentation