Question

Every once and a while I hit a button on my web application and I get no response. The “button” initiates an ajax call. My guess is that there is heavy web traffic…and it times out or similar. Is there a maximum wait time for ajax responses from the server? Is there a way to log this behavior. Here is my ajax code.

 var Ajax = {
    createAjaxObject: function()
    {
        var request;
        try
        {
            request = new XMLHttpRequest();
        }
        catch(error)
        {
            try 
            {
                request = new ActiveXObject("Msxml2.XMLHTTP");
            }
            catch(error)
            {
                try
                {
                    request = new ActiveXObject("Microsoft.XMLHTTP");
                }
                catch(error)
                {
                    request = false;
                }
            }
        }
        return request;
    },

    useAjaxObject: function( path, param, ajax_func, html_div )
    {
        var object = new Ajax.createAjaxObject();
        object.open( "POST", path, true );
        object.setRequestHeader( "Content-type", "application/x-www-form-urlencoded" );
        object.setRequestHeader( "Content-length", param.length );
        object.setRequestHeader( "Connection", "close" );
        object.onreadystatechange = function()
        {
            if( this.readyState === 4 )
            {
                if( this.status === 200 )
                {
                    ajax_func( this.responseText, html_div );
                }
                else
                {
                    Ajax.repeatUseAjaxObject( path, param, ajax_func, html_div );
                    return false;
                }
            }
        };
        object.send( param );
        return true;
    },
    repeatUseAjaxObject: function( path, param, ajax_func, html_div )
    {
        var state = false,
            count = 1;
        while(state === false && count <= 5)
        {
            state = Ajax.useAjaxObject( path, param, ajax_func, html_div );
            if( count !== 1 )
            {
                alert( 'Ajax Object Use Failed ');
            }
        count++;
        }
    }

Answer 1

Sometimes the response could be of the wrong expected type, or the server is returning an error status code/page instead of the actual requested information. A good way to check the full response (or if there really is a lack of a response) is with a good HTTP traffic proxy debugger such as:

Fiddler
http://fiddler2.com/fiddler2/ (Free)

or Charles
http://www.charlesproxy.com/

They will give you full information about the life cycle of each web request. As far as minimum or maximum times, generally the server has a setting for the timeout of any given request.

Client Site Timeout: From the jQuery Api… Not sure since you’re rolling your own.

Set a timeout (in milliseconds) for the request. This will override any global timeout set with $.ajaxSetup(). The timeout period starts at the point the $.ajax call is made; if several other requests are in progress and the browser has no connections available, it is possible for a request to time out before it can be sent.