MapJAX: Data Structure Abstractions for Asynchronous Web Applications

The current approach to developing rich, interactive web applications relies on asynchronous RPCs (Remote Procedure Calls) to fetch new data to be displayed by the client. We argue that for the majority of web applications, this RPC-based model is not the correct abstraction: it forces programmers to use an awkward continuation-passing style of programming and to expend too much effort manually transferring data. We propose a new programming model, MapJAX, to remedy these problems. MapJAX provides the abstraction of data structures shared between the browser and the server, based on the familiar primitives of objects, locks, and threads. MapJAX also provides additional features (parallel for loops and prefetching) that help developers minimize response times in their applications. MapJAX thus allows developers to focus on what they do best-writing compelling applications-rather than worrying about systems issues of data transfer and callback management.

We describe the design and implementation of the MapJAX framework and show its use in three prototypical web applications: a mapping application, an email client, and a search-autocomplete application. We evaluate the performance of these applications under realistic Internet latency and bandwidth constraints and find that the unoptimized MapJAX versions perform comparably to the standard AJAX versions, while MapJAX performance optimizations can dramatically improve performance, by close to a factor of 2 relative to non-MapJAX code in some cases.