Long polling: Max Pool size reached - mysql

Question

I'm using long polling in my website to check for any new data in MySQL database and then updating the ui,
actually if the website is up for longer than +- one hour the website just broke up by giving the following error:
500 {"Message":"error connecting: Timeout expired. The timeout period elapsed prior to obtaining a connection from the pool. This may have occurred because all pooled connections were in use and max pool size was reached.","StackTrace":" at MySql.Data.MySqlClient.MySqlPool.GetConnection()\r\n at MySql.Data.MySqlClient.MySqlConnection.Open()\r\n at VisualReservation._Default.getSale() in C:\\Users\\imytyuk\\Documents\\Visual Studio 2017\\Projects\\VisualReservation\\VisualReservation\\Default.aspx.vb:line 109","ExceptionType":"MySql.Data.MySqlClient.MySqlException"}
So it seems that there are too many connections to the database and it just get broken..
Actually the error is thrown by the following method that is called from long polling
function getTavoli(data_tavoli, salaSelect, pooling) {
$.ajax({
type: "POST",
url: "Default.aspx/SetTavoli",
data: JSON.stringify({ data: moment(data_tavoli).format('YYYY-MM-DD') }),
contentType: "application/json; charset=utf-8",
dataType: "json",
success: function (r) {
var ingiorno = $('#ingiorno').val();
var fngiorno = $('#fngiorno').val();
var insera = $('#insera').val();
var fnsera = $('#fnsera').val();
ingiorno = ingiorno.split(":")[0];
fngiorno = fngiorno.split(":")[0];
insera = insera.split(":")[0];
fnsera = fnsera.split(":")[0];
if ($('#titleTurni').attr('data-turno') == "giorno") {
Range = ingiorno * 4
Fine = (fngiorno * 4) + 1;
orainizio = ingiorno;
orafine = fngiorno;
} else {
Range = insera * 4
Fine = (fnsera * 4) + 1;
orainizio = insera;
orafine = fnsera;
}
data = r.d;
data = $.parseJSON(data);
if (pooling) {
if (JSON.stringify(data) === prevData) {
return;
} else {
recreateTabs();
prevData = JSON.stringify(data);
}
}
$('#listBodyMobile').empty();
$('#bodyGiorno').empty();
$('#bodySera').empty();
getInfo(data_tavoli);
$.each(data, function (i, item) {
// doing all stuff with items
});
});
},
error: function (xhr, status, errorThrow) {
console.log(xhr.status + " " + xhr.responseText);
}
});
}
The polling is called in the following way
poolingTav = setInterval(() => {
getTavoli(new Date($("#day").attr('data-giorno')), $("#titleSale").attr('data-numsala'), true);
}, 50000)
While the SetTavoli in the server side looks like the following
<WebMethod()>
<ScriptMethod(ResponseFormat:=ResponseFormat.Json)>
Public Shared Function SetTavoli(ByVal data As String) As String
Dim con As MySqlConnection = New MySqlConnection
con.ConnectionString = "CONNSTRING"
DeleteSTB(con)
Dim strSql As String = "QUERY"
Dim dtb As New DataTable
con.Open()
Dim sqlCmd As New MySqlCommand(strSql, con)
Dim sqlDad As New MySqlDataAdapter(sqlCmd)
sqlDad.Fill(dtb)
con.Dispose()
dtb.Columns(0).ColumnName = "data"
dtb.Columns(1).ColumnName = "orain"
dtb.Columns(2).ColumnName = "oraout"
dtb.Columns(3).ColumnName = "numtav"
dtb.Columns(4).ColumnName = "numcop"
dtb.Columns(5).ColumnName = "email"
dtb.Columns(6).ColumnName = "tel"
dtb.Columns(7).ColumnName = "note"
dtb.Columns(8).ColumnName = "nome"
dtb.Columns(9).ColumnName = "id"
dtb.Columns(10).ColumnName = "stato"
Return Json(dtb)
End Function
So i was wondering what i'm doing wrong and how i could fix that issue still by using long polling...
To the website there will be connected lot of users with their own account and will be accessing their own databases..