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Auditing your Windows Javascript UWP application in production

Since the launch of Windows 8, I’m writing native Windows applications using HTML and JavaScript, for the Windows store and for enterprise applications. Believe it or not but I’m doing it full time and, so far, I’m really enjoying it. I know many people will disagree, especially in the Windows ecosystem, but I’m really enjoying the productivity and the expressiveness you get by writing rich client applications using HTML. And the beauty with Windows 8, and now Windows 10, is that you have full access in JavaScript to the Windows API, from rich file access, to sensors, Cortana integration, notifications, etc.

Even better, with Windows 10 and the Universal Windows Platform (or UWP) you could write one single application using HTML and JavaScript that will run on Windows desktop, laptop, tablet, phone, IoT devices, Xbox, Hololens and probably much more.

If you are familiar with the web ecosystem, you could also very easily reuse most or all of your skills and application code and use it to build awesome websites, or target other devices, with Github electron to make a Mac OsX version, or use Cordova or React native to reach iOS or Android. It really is an exciting time for web developpers.

As exciting as those experiences have been, there are a few things that are still frustrating. No matter what technology you use for development, one of them is the ability to detect and troubleshoot problems when your application have been released into the wild. Visual Studio is really great and provide many tools to help debug and audit your app on your dev box, but for troubleshooting applications in production, you’re naked in the dark.

Luckily when using web technologies, you could use some wonderful tools like Vorlon.js. This tool is really great because you could target any device, without any prerequisite. You have nothing to install on the client to have great diagnostics from your app.
I previously explained how to use Vorlon.js in production, and how to use it with your JavaScript UWP, follow those post if you want to setup the stage. In this post, we will see an overview of what you can achieve with Vorlon.js for a Windows UWP app in production, and a few guidance. What we will see is not specific to a JavaScript UWP. You could use the same things to debug a Webview in a C# or C++ application.

Inspect the DOM

Vorlon.js is designed from the ground with extensibility in mind. It features many plugins, and you could really easily write your own (we will talk more on that later). One of the most usefull for frontend applications is the DOM explorer. It’s very much like the tools you will find in the developper tools of your favorite browser.
For troubleshooting issues in production, it is very interesting to see what appened into the DOM, what styles are applyed, check the current size of the user screen, etc.



Watch the console

Another core plugin of Vorlon is the console. It will shows all console entries in your dashboard. If you put meaningful console logging into your app, this plugin is insanely usefull because you see in (almost) realtime what the user is doing, which is key to reproduce the issue. With some luck (and coding best practices), you could also have errors popping directly in the console with the stack trace (if the Promise god is with you). The console also feature an « immediate window » where you could issue simple JavaScript commands.


Check objects value

You could also have access to global JavaScript variables using Object explorer. This plugin allow you to watch values from your objects, and explore graph of objects. It’s always interesting to be able to keep an eye on your application state when trying to troubleshoot your application.


Monitoring CPU, memory, disk, …

You sometimes have to face more insidious bugs, like memory leaks, that usually requires advanced debugging tools. In the comfort of your dev box, you could use IDEs like Visual Studio to diagnose those bugs with specific tools. Modern browsers usually have similar tools, but does not have APIs to check things like memory or CPU that you could use remotely. Fortunately, when you are targeting Windows UWP, you could have access to all modern Windows APIs, and especially those about diagnostics.

That’s why the Vorlon team implemented a plugin specific to Windows UWP. It uses WinRT APIs for diagnostics and for different metadata from the client. For now, this plugin is not released, and you will have to look at the dev branch to try it out.


From the application metadata, you will get infos, such as its name, but also the application version, current language, and device family.


You will also have a glimpse at the network kind and status, and the battery level of the device.

It enables you to monitor the CPU, the memory and disk I/O. It’s especially usefull to track memory leaks, or excessive resources consumption.


And much more…

You have many more plugins within Vorlon that will help you diagnose your app, monitor xhr calls, explore resources like localstorage, check for accessibility and best practices, and so on. We cannot cover them all in one post, but I hope you get a decent idea of the many possibilities it is unlocking to help you improve your applications, both during development and more than anything, in your production environment. It’s especially usefull for mobile applications such as Windows UWP.

Writing plugin for Vorlon.js is really easy. You have to implement one javascript class for the client, and one other for displaying results in the dashboard. Writing a simple plugin can sometimes helps you save a lot of time because it can helps you analyse the problem when and where they occur. If you are proud of your plugin, submit it back to Vorlon.js !

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