Communications of the ACM
BLeak: Automatically Debugging Memory Leaks in Web Applications
Credit: Cliqz
Memory leaks in web applications are pervasive and difficult to debug. Leaks degrade responsiveness by increasing garbage collection costs and can even lead to browser tab crashes. Previous leak detection approaches designed for conventional applications are ineffective in the browser environment. Tracking down leaks currently requires intensive manual effort by web developers, which is often unsuccessful.
This paper introduces BLEAK (Browser Leak debugger), the first system for automatically debugging memory leaks in web applications. BLEAK'S algorithms leverage the observation that in modern web applications, users often repeatedly return to the same (approximate) visual state (e.g., the inbox view in Gmail). Sustained growth between round trips is a strong indicator of a memory leak. To use BLEAK, a developer writes a short script (17-73 LOC on our benchmarks) to drive a web application in round trips to the same visual state. BLEAK then automatically generates a list of leaks found along with their root causes, ranked by return on investment. Guided by BLEAK, we identify and fix over 50 memory leaks in popular libraries and apps including Airbnb, AngularJS, Google Analytics, Google Maps SDK, and jQuery. BLEAK'S median precision is 100%; fixing the leaks it identifies reduces heap growth by an average of 94%, saving from 0.5MB to 8MB per round trip.
1. Introduction
Browsers are one of the most popular applications on both smartphones and desktop platforms. They also have an established reputation for consuming significant amounts of memory. To address this problem, browser vendors have spent considerable effort on shrinking their browsers' memory footprints5, 11 and building tools that track the memory consumption of specific browser components.4, 10
Memory leaks in web applications only exacerbate the situation by further increasing browser memory footprints. These leaks happen when the application references unneeded state- preventing the garbage collector from collecting it. Web application memory leaks can take many forms, including failing to dispose of unneeded event listeners, repeatedly injecting iframes and CSS files, and failing to call cleanup routines in third-party libraries. Leaks are a serious concern for developers since they lead to higher garbage collection frequency and overhead. They reduce application responsiveness and can even trigger browser tab crashes by exhausting available memory.
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