Client-Side Monitoring Tools

Client-Side Performance Testing & Tools Importance and Introduction

Client side performance testing & tools have their own importance. If you’re worried about the performance of your web application, you need to test and analyze not only with what happens on the server but also with what happens in the browser. Some commercial performance-monitoring solutions already take this into account, allowing performance engineers to see how long it takes for elements to render, and then to execute, on your users’ browsers. There is also no shortage of open-source tools available for you to check and improve the ways in which your client-side programs are executing and working.

Page load time is one of the most important metrics in web applications. According to Yahoo, around 80% of application response time is spent downloading elements such as images, stylesheets, scripts, etc. To speed up response time requires strong servers and a well prepared and tested application.

This is where performance tests come in. They analyze the speed, scalability and stability of an application, checking for memory leaks, how the application works under a certain load, and look for any bottlenecks.

To provide better feedback, performance tests are divided into two types: server-side and client-side. When you are testing server-side code, you are testing the logic and readiness of your application. When you are testing the client-side, you are doing end-to-end testing.

To verify if an application is fast and efficient enough, we use client-side performance tests. This means checking the response time of a web application from the point of view of a single user. We execute these tests against two scenarios:

  1. A user coming to the web page for the first time (without cache).
  2. A user coming back to our page (with cache).

Client-Side Performance Considerations

The client-side code is written in JavaScript. The code, whether inline in <script> tags or retrieved from a remote server, executes whenever the browser’s parser gets to that part of the page. If you have JavaScript at the top of the page, it’ll be executed when the parser gets to it, potentially delaying the rendering of the rest of your page.

If your JavaScript is at the bottom, the parser will execute it only after parsing and rendering the rest of the page. This is why so many developers learned to put their JavaScript commands inside a “document-ready” callback function. In that way, the code was executed only once the entire page had been loaded.

When loading JavaScript from remote servers means that the time it takes to render a page depends not just on the server speed, the network bandwidth, and the page’s complexity, but also on the servers and networks serving such JavaScript, as well as those pages’ complexity.

Consolidating all our JavaScript files into a single file has many advantages. It means the user’s browser needs to download a single file, rather than many of them. If you include all of the JavaScript needed on your site in a single file, it also means that the file needs to be loaded only a single time.

On every subsequent page load, the JavaScript will be mentioned, but it won’t be downloaded, because it’ll already be cached in the browser’s memory. This turns out to be extremely effective because compression algorithms work well wrt performance.

It is always a good practice to run your JavaScript code with “minimizer” or “minified” which removes comments, extra spaces and everything else that is not necessary for client-side programs to run. Also, by combining and compressing the files we can reduce the JavaScript size that is being sent to users’ browsers and ensure that is loaded only once per visit to your application/website.

Front-End Performance Testing Challenges

Performance depends almost entirely on everything. The greatest threat to performance was likely to be the connection speed, followed by server overload. The browser spent much of its time with a fully loaded page of HTML, just waiting for graphics and other content.

  • How quickly basic page features load?
  • Visible text.
  • Graphics.
  • Formatting and layout (CSS).
  • Functional elements (buttons, links, forms, etc.).
  • Understanding the priorities on how quickly functional elements become responsive (at all) to user actions.
  • How quickly functional elements are able to carry out user requests.
  • How long it takes for the entire page and all of its functionality to load.
  • Matching the exact real-world environment with real content and new code.
  • Identifying which elements are important in a Page and when do they load?
  • Concluding the issue – Is the issue Front end or Server-side?