CSR: Small: SmartEdge for Low Latency and Consistent Mobile Web Applications

此计算机系统研究(CSR)核心区项目专注于实现Web应用程序的低端到端延迟(低于100毫秒)这一重大挑战。低于100毫秒的延迟使Web应用程序感觉到与运行在台式机/移动设备上的本地应用程序一样灵敏，这对增强用户体验、更快采用云计算以及电子商务收入具有巨大影响。实现如此低的延迟尤其具有挑战性，因为(A)今天的网络下载过程不太适合高延迟蜂窝网络，以及(B)网络应用程序中更个性化、更动态的内容的趋势，这使得很难在靠近用户的地方缓存可变的网络内容；存储通常保存在远程的中央数据中心(DC)中。以前在缓存动态内容方面的许多工作只提供了弱的一致性保证(通常是最终的一致性)，但许多交互场景需要更强的因果模型。该项目将导致设计和评估SmartEdge，它为移动Web应用程序提供低延迟，同时保证可变后端存储的因果一致性。该项目通过一种名为SmartEdge的综合方法来解决上述挑战，该方法将应用程序功能和后端存储都移动到网络边缘。为了解决蜂窝设备和桌面之间的延迟差距，这项研究在云上采用了冗余执行，并主动将数据推送到客户端。SmartEdge利用在Web应用程序环境中可能近似的冗余执行这一事实，大幅减少冗余计算的开销，从而使边缘能够扩展到数十万个客户端。为了应对可扩展、一致的后端存储的挑战，SmartEdge(A)仅部分复制DC子集中的数据(与需要完全复制所有DC中的所有数据的现有技术不同)，以及(B)支持大规模和分层边缘缓存(不同于仅限于少量DC的现有地理复制存储系统)。这些技术不仅可以通过将数据放置在离用户更近的地方来缩短延迟，还可以将复制成本降低一个数量级。此外，该项目将让博士、硕士和本科生广泛参与研究活动，项目结果将在主要的科学会议上公布。为了支持与云计算相关的教育活动，将发布一套“盒装数据中心”。

This Computer Systems Research (CSR) Core Area project focuses on the grand challenge of achieving low end-to-end latency (under 100 ms) for web applications. Sub-100-ms latencies makes web applications feel as responsive as local applications that run on desktops/mobiles, which has enormous implications for enhanced user experiences, faster adoption of cloud computing, and for e-commerce revenues. Achieving such low latency is especially challenging because (a) todays web download process is a poor fit to high-latency cellular networks, and (b) the trend in web applications toward more personalized, dynamic content which makes it difficult to cache mutable web content close to users; the storage is typically held in distant centralized data-centers (DCs). Much of the previous work in caching dynamic content offers only weak consistency guarantees (typically, eventual consistency), but many interactive scenarios require the stronger causal model. The project will result in the design and evaluation of SmartEdge which offers low latency for mobile web applications while guaranteeing causal consistency for mutable backendstorage.This project addresses the above challenges via a comprehensive approach called SmartEdge which moves both the application functionality and the back-end storage to the network edge. To address the latency gap between cell devices and desktops, this research employs redundant execution on the cloud and proactively pushing data to the client. SmartEdge leverages the fact that redundant execution may be approximate in the context of web applications to drastically reduce the overheads of redundant computation, which enables the edge to scale to hundreds of thousands of clients. To address the challenge of scalable, consistent backend storage, SmartEdge (a) only partially replicates data in a subset of DCs (unlike existing techniques which require full replication of all data in all the DCs), and (b) supports large-scale and hierarchical edge caching (unlike existing geo-replicated storage systems that are limited to a small number of DCs). These techniques not only enable latency reduction by placing data closer to users but also achieve an order of magnitude lower replication cost. In addition, the project will extensively involve Ph.D, Masters and undergraduate students in research activities, and results from the projects will be published in premier scientific conferences. To support educational activities related to cloud computing, a "data-center-in-a-box" kit will be released.