JavaScript Error Reporting with Splunk

Keeping track of new browser releases these days can be really challenging. It is less than ideal if your payment processor is throwing a JavaScript onsubmit exception effectively canceling all transactions.

Here is a little technique for indexing JavaScript exceptions in your production and development environments using Splunk.

In JavaScript create an onerror event handler that makes an HTTP request to a server that has access logs indexed by Splunk.

    function JSErrorLogger(httpBeacon){
        var self = this;
        self.handler = function(msg, url, line){
            var log = {
                "date":new Date(),
                "type":"jserror",
                "line":line,
                "msg":msg,
                "url":url
            }
            var logStr = "";
            for(var i in log){
                logStr += i + ":" + log[i] + " ";
            }
            var imgObj = new Image();
            imgObj.src = httpBeacon + "?" + logStr;
        };
        self.JSErrorLogger = function(){
            window.onerror = self.handler;
        }();
    }

Make sure that this JavaScript is the very first item executed by the interpreter, ensuring all exceptions are caught by the event handler.

Instantiate the class with a URI that points to a beacon on a machine that has Splunk indexing the access log. You may want to set some environment variables in JavaScript that turn logging on for only testing and production machines.

   //if environment test or production
   var splunkJSErrorIndexer = new JSErrorLogger("http://somedomain.com/beacon.gif");

That’s it, now you can empirically understand JavaScript exceptions being raised, set blackberry alerts and correlate ui stability issues to deploys:)

Happy JavaScript Monitoring!