Jquery: the script stops when ajax request fails with error 500

Question

I have a script that sends ajax request in intervals and ideally it should never cease to work.

    <script type="text/javascript">
    var delay = 750;
    window.setInterval(endlessJob, delay);
    function endlessJob() {
        //read from endless steam of data
        var data = getData();
        sendAjax(data);
    }

    function sendAjax(data) {
         $.ajax({
            url: "url",
            jsonp: "jsonp",
            dataType: "jsonp",
            data: {
                q: data
            },
            success: function (res) {
                doSomething();
            },
            error: function (jqXHR, textStatus, errorThrown) {
                console.log('ajax error! ' + errorThrown.message + "\n status: " + textStatus);
                //should resume endless job, but the script fails with error(((((((((((
                 window.setInterval(endlessJob, delay);
            }
        });
    }
</script>

And then there's the problem: after a number of requests, ussually it's between 1000 and 2000, the request fails with Internal Server Error 500 and the function never resumes. Have already tried try/catch, but with no success(. Basically i need to just swallow the error and continue the script. Can someone assist me please?

Answer 1

You are making a call to the server every 3/4 of a second over a thousand times. Eventually you will have calls being made before the previous call has had enough time to complete. If you want your script to run for a very long time i recommend you either extend your delay to say maybe 1500-2000 (1.5-2 seconds depending on your server) or change your code to require a callback. This way the next call won't be initialized until the previous one has been completed. Here is your code modified with a callback. I did not have time to test it but hopefully it will give you a general idea of how to write it with callbacks.

<script>

    function start() {
        var data = getData();

        sendAjax(data, function(callbackText) {
            console.log(callbackText);
            start(); // the previous ajax call is done. we may now start the next one
        });
    }

    function sendAjax(data, callback) {
        $.ajax({
            url: "url",
            jsonp: "jsonp",
            dataType: "jsonp",
            data: {
                q: data
            },
            success: function(res) {
                doSomething();
                callback("This call is done. Now moving on to the next one.");
            },
            error: function(jqXHR, textStatus, errorThrown) {
                console.log('ajax error! ' + errorThrown.message + "\n status: " + textStatus);
                //should resume endless job, but the script fails with error(((((((((((
                window.setInterval(endlessJob, delay);
            }
        });
    }

    start(); // start the entire process
</script>