LeakSpot: detection and diagnosis of memory leaks in JavaScript applications

Abstract

The migration of application logic to the client side of modern web applications and the use of JavaScript as the main language for client-side development have made memory leaks in JavaScript an issue for web applications. Client-side web applications communicate with the server asynchronously, remaining on the same web page during their lifetime. Thus, even minor memory leaks can eventually lead to excessive memory usage, negatively affecting user-perceived response time and possibly causing page crashes. To detect memory leaks and guide developers in fixing the leaks quickly and easily, this paper introduces LeakSpot, a tool that creates a run-time heap model by modifying the application code in a browser-agnostic way to record object allocations, accesses, and references created to objects. LeakSpot reports those allocation sites causing the leaks instead of all the leaky allocation sites. It also identifies the locations in the code where leaked objects are accumulated, for example, the locations where a reference from a data structure is created but forgotten to be removed by the developer. To facilitate debugging and fixing the leaks, for every leaked object, LeakSpot reports all the locations in the code that create a reference to the object. To confirm usefulness and efficacy of LeakSpot experimentally, we have used LeakSpot to find and fix four memory leaks in a JavaScript benchmark suite and in open-source web applications. LeakSpot is also shown to be effective in pointing out the potential causes of three leaks in large and popular web applications. Copyright © 2016 John Wiley & Sons, Ltd.