Performance of Multi-threaded Web Applications using Web Workers in Client-side JavaScript

Abstract: Context - Software applications on the web are more commonly used nowadays than before. As a result of this, the performance needed to run the applications is increasing. One method to increase performance is writing multi-threaded code using Web Workers in JavaScript. Objectives - We will investigate how using Web Workers can increase responsiveness, raw computational power and decrease load time. Additionally, we will conduct a survey that targets software developers to find out their opinions about performance in web applications, multi-threading and more specifically Web Workers. Realization (Method) - We created three experiments that concentrate on the areas mentioned above. The experiments are hosted on a web server inside an isolated Docker container to eliminate external factors as much as possible. To complement the experiments we sent out a survey to collect information of developers' opinions about Web Workers. The criteria for the selection of developers were some JavaScript experience. The survey contained questions about their opinions on switching to a multi-threaded workflow on the web. Do they experience performance issues in today's web applications? Could Web Workers be useful in their projects? Results - Responsiveness shifted from freezing the website to perfect responsiveness when using Web Workers. Raw computational power increased at best 67% when using eight workers with tasks that took between 100 milliseconds and 15 seconds. Over 15 seconds, sixteen workers improved the computational power further with around 3% - 9% compared to eight workers. At best the completion time decreased with 74% in Firefox and 72% in Chrome. Using Web Workers to help with load time gave a big improvement but is somewhat restricted to specific use cases. Conclusions - Using Web Workers to increase responsiveness made an immense difference when moving tasks that is affecting the users responsiveness to background threads. Completion time for big computational tasks was quicker in use cases where you can split the workload to separate portions and use multiple threads in parallel to complete the tasks. Load time can be improved with Web Workers by completing some tasks after the page is done loading, instead of waiting for all tasks to complete and then load the page. The survey indicated that many have performance in mind and would consider writing code in a multi-threaded way. The knowledge about multi-threading and Web Workers was low. Although, most of the participants believe that Web Workers would be useful in their current and future projects, and are worth the effort to implement.