By repeatedly crawling and saving web pages over time, web archives (such as the Internet Archive) enable users to visit historical versions of any page. In this paper, we point out that existing web archives are not well designed to cope with the widespread presence of JavaScript on the web. Some archives store petabytes of JavaScript code, and yet many pages render incorrectly when users load them. Other archives which store the end-state of page loads (e.g., screen captures) break post-load interactions implemented in JavaScript.
To address these problems, we present Jawa, a new design for web archives which significantly reduces the storage necessary to save modern web pages while also improving the fidelity with which archived pages are served. Key to enabling Jawa’s use at scale are our observations on a) the forms of non-determinism which impair the execution of JavaScript on archived pages, and b) the ways in which JavaScript’s execution fundamentally differs between live web pages and their archived copies. On a corpus of 1 million archived pages, Jawa reduces overall storage needs by 41%, when compared to the techniques currently used by the Internet Archive.
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Horcrux: Automatic JavaScript Parallelism for Resource-Efficient Web Computation
Web pages today commonly include large amounts of JavaScript code in order to offer users a dynamic experience. These scripts often make pages slow to load, partly due to a
fundamental inefficiency in how browsers process JavaScript content: browsers make it easy for web developers to reason about page state by serially executing all scripts on any frame
in a page, but as a result, fail to leverage the multiple CPU cores that are readily available even on low-end phones.
In this paper, we show how to address this inefficiency without requiring pages to be rewritten or browsers to be modified. The key to our solution, Horcrux, is to account
for the non-determinism intrinsic to web page loads and the constraints placed by the browser’s API for parallelism. Horcrux-compliant web servers perform offline analysis of all the JavaScript code on any frame they serve to conservatively identify, for every JavaScript function, the union of the page state that the function could access across all loads of that page. Horcrux’s JavaScript scheduler then uses this information to judiciously parallelize JavaScript execution on the client-side so that the end-state is identical to that of a serial execution, while minimizing coordination and offloading overheads. Across a wide range of pages, phones, and mobile networks covering web workloads in both developed and emerging regions, Horcrux reduces median browser computation delays by 31-44% and page load times by 18-37%.
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- Award ID(s):
- 2152313
- NSF-PAR ID:
- 10323103
- Date Published:
- Journal Name:
- 15th USENIX Symposium on Operating Systems Design and Implementation (OSDI)
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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