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(),
            var logStr = "";
            for(var i in log){
                logStr += i + ":" + log[i] + " ";
            var imgObj = new Image();
            imgObj.src = httpBeacon + 
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Hey Browser, You’ve Got Tail!

For those interested in monitoring real-time data being consumed by Splunk we’ve introduced a new feature called Live Tail to the latest preview release. Additionally, we’ve added a nifty new REST endpoint /v3/splunk/tail for your custom application needs.

Live Tail

More information can be found in these videos:

  • A quick walkthrough of the new preview release feature Live Tail, its UI, and some sample code – See Video
  • An overview of the architecture used to integrate real-time data from Splunk Live Tail in a web browser. Challenges and workarounds when using JavaScript/Flash hybrids – See Video

Happy Streams!…

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Flash/AS3 URLStream Memory Leak

Lately we have been doing some work with persistent connections. If you are familiar with Comet the Flash/AS3 URLStream class provides an interesting alternative. The URLStream class exposes raw binary data as it is downloaded.

Unfortunately, this week we ran into a rather tricky memory leak when using this nifty class. An event listener was subscribed to the progress event and over time memory usage steadily increased to a point of making the browser inoperable.

After a little digging we narrowed the problem down to the URLStreams usage of the ByteArray. It seems as if URLStream was reallocating a buffer for the array and the short turn around time (on the reads) was not giving the garbage collector enough …

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JavaScript Hybrids (Extending the browser) – Part 1

I deeply enjoy browser programming, however sometimes I wish it could do more. Things like sockets, streams, audio and improved file system handling would be a real treat. Man would it be fresh if I had access to this functionality in JavaScript.

Now this is going to sound pretty circa 98, but several main stream browser plugins support a JavaScript communication layer. According to the Millward Brown survey plugin installations of Flash (99%) and Java (85%) are pretty ubiquitous.

Flash/JavaScript Communication
The Flash ExternalInterface class enables communication between JavaScript and the Flash Player. ExternalInterface was first introduced in ActionScript 1.0; so Flash Player 8 is the minimum plugin version required.
From JavaScript

  • Call an ActionScript function
  • Pass arguments
  • Return a
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JavaScript Key Binding

Keyboard shortcuts are a powerful and useful UI interaction pattern. Surprisingly, detecting and binding to keyboard events is not a simple task in browsers.


Meet E.Key, a JavaScript key event listener utility that tries to help. VI and Emacs browser key bindings, no problem!

Happy keyboard shortcuts,
Carl (Doc Yes) …

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