Dynamic Flot chart using Ajax

Question

I'm new to javascript and flot and hope someone can help me with this problem I'm having. What I'm trying to achieve it have a dynamic flot graph on a page.

The data for the series that is to be plotted is in a file that will get updated every few seconds. I want the flot graph to read the data file every few seconds and be updated with the new data.

Here's the code I've got which isn't working. The graph displays ok on page load, but just doesn't get updated every 5 seconds.

Any help is much appreciated.

   $(function () {

var dataFolder = "http://localhost/graphdata/";

/***********************************************************************
 *             Function to get series data from a file
 ***********************************************************************/
function getSeriesData(file) {
    var url= dataFolder + file;
    var data = null;
    $.ajax({
        async: false,
        url: url,
        method: 'GET',
        dataType: 'json',
        success: function(datasets){
            data = datasets;
        },
        error: function(error,text,http){
            alert(error + " " + text + " " + http);
        }
    });  

    return data;
}
    var plot = $.plot($("#placeholder"),
        [
            {label: "A", data: getSeriesData("dataA.txt")},
            {label: "B", data: getSeriesData("dataB.txt")},
            {label: "C", data: getSeriesData("dataC.txt")}
        ],
        {
            series: {
                lines: {
                    color: "red",
                    show: true
                },
                points: {
                    show: true
                },
                shadowSize: 0,
                hoverable: true
            },
            colors: ["red", "blue", "green"],
            yaxis: {
                min: 0,  ticks:5
            },
            xaxis: {
                mode: 'time',
                timeformat: '%H:%m',
                show: false
            },
            legend:{
                show: true
            },
            grid:{
                color: "green",
                show: true,
                backgroundColor: "white",
                hoverable: true
            }
        }
);

var updateInterval = 1000 * 5;
function update() {

    plot.setData([
                          {label: "A", data: getSeriesData("dataA.txt")},
                          {label: "B", data: getSeriesData("dataB.txt")},
                          {label: "C", data: getSeriesData("dataC.txt")}
                      ]);
    plot.setupGrid();
    plot.draw();

    setTimeout(update, updateInterval);
}
update();});

Answer 1

I figured it out. The ajax call for the file was being cached in the browser so any further calls for the same file would have been returned from cache, making it look like no updates to the graph were happening. Switch caching of in the function and it works fine now.

function getSeriesData(file) {
    var url= dataFolder + file;
    var data = null;
    $.ajax({
        async: false,
        cache: false,
        url: url,
        method: 'GET',
        dataType: 'json',
        success: function(datasets){
            data = datasets;
        },
        error: function(error,text,http){
            alert(error + " " + text + " " + http);
        }
    });  

    return data;
}