Unable to display highcharts graphs with setextremes - flask

Question

I am collecting info from weather sensors(every 5 mins) and through the days and months, the amount of records is huge and render the chart takes for ever....It is working ,but the delay is too high... So instead of displaying all the values at once, I want to make the graph based on range of dates selected, and get data accordingly.
I am using python , sqlite3 and Flask and trying to copy this example from Highcharts
https://jsfiddle.net/gh/get/library/pure/highcharts/highcharts/tree/master/samples/stock/demo/lazy-loading/
In the example they use php , which here is the code
https://github.com/highcharts/highcharts/blob/master/samples/data/from-sql.php
This is my setextreme function in the html page
function setExtremes(e)
// detect zoom button
{
if(typeof(e.rangeSelectorButton)!== 'undefined')
{
if (e.rangeSelectorButton.type=='all')
{
var chart = Highcharts.charts[0];
chart.showLoading('Loading data from server...');
$.getJSON('http://192.168.0.74:5000/rango?start=' + Math.round(e.min) +'&end=' + Math.round(e.max) + '&callback=?', function (data) {
// Arrange data
alert('I am in')
for (i = 0; i< data.length; i++)
{
processed_json_temperatura.push(data[i][0], data[i][1]);
processed_json_presion.push(data[i][0], data[i][2]);
processed_json_humedad.push(data[i][0], data[i][3]);
processed_json_lluvia.push(data[i][0], data[i][4]);
processed_json_horas_frio.push(data[i][0], data[i][5]);
}
temperatura_matriz = listToMatrix( processed_json_temperatura,2);
presion_matriz = listToMatrix( processed_json_presion,2);
humedad_matriz = listToMatrix( processed_json_humedad,2);
lluvia_matriz = listToMatrix( processed_json_lluvia,2);
horas_frio_matriz = listToMatrix(processed_json_horas_frio,2);
//update graphs with new values
chart.series[0].setData(temperatura_matriz);
chart.series[1].setData(presion_matriz);
chart.series[2].setData(humedad_matriz);
chart.series[3].setData(lluvia_matriz);
chart.series[4].setData(horas_frio_matriz);
chart.hideLoading();
});
}
}
}
On server side, this is my python code with flask
#app.route("/rango")
def rango():
start=request.args.get('start')
end=request.args.get('end')
range = int(end)/1000 - int(start)/1000
# find the right table
# two days range loads minute data
if (range < 2 * 24 * 3600 * 1000):
connection = sqlite3.connect("/var/www/nueva_estacion.db")
cursor = connection.cursor()
cursor.execute("select (julianday(timestamp)-2440587.5)*86400000, round(temp1,2) as temp1, presion, round(humedad,2) as humedad, lluvia,aux1 from raw_all_sensors where datetime(timestamp) >=datetime('now', '-6 Day')")
results = cursor.fetchall()
print json.dumps(results)
return json.dumps(results)
When I click the zoom button(on highstock actually) I do see the message " Loading data from Server ..." but never shows the new graphs and never get "I am in" console message..
When monitoring the messaging on server side, I do get
192.168.0.122 - - [22/May/2019 19:47:22] "GET /rango?start=1558050049000&end=1558551372000&callback=jQuery18307335687220269529_1558565228146&_=1558565238543 HTTP/1.1" 200 -
where is clear start date, end date and then I do not understand the callback and the numbers that follow.
Just in case, this is the info coming from server
[1558546562999.989, 17.82, 1021, 76.15, 0, 1]
Can anyone bring some light here?