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

这个计算机系统研究（CSR）核心领域项目专注于为Web应用程序实现低端到端延迟（低于100 ms）的巨大挑战。低于100毫秒的延迟使Web应用程序的响应速度与运行在桌面/移动设备上的本地应用程序一样快，这对增强用户体验、更快地采用云计算和电子商务收入都有巨大的影响。实现这样的低延迟是特别具有挑战性的，因为（a）当今的web下载过程不太适合高延迟蜂窝网络，以及（B）web应用中朝向更加个性化的动态内容的趋势，这使得难以将可变web内容高速缓存到用户附近;存储通常保持在远程集中式数据中心（DC）中。以前在缓存动态内容方面的许多工作只提供了弱一致性保证（通常是最终一致性），但许多交互式场景需要更强的因果模型。该项目将导致SmartEdge的设计和评估，它为移动的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。该项目通过一种称为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利用冗余执行在Web应用程序的上下文中可能是近似的这一事实，大大减少了冗余计算的开销，从而使边缘能够扩展到数十万个客户端。为了解决可扩展的、一致的后端存储的挑战，SmartEdge（a）仅部分地复制DC的子集中的数据（不像现有技术，其需要在所有DC中完全复制所有数据），以及（B）支持大规模和分层的边缘缓存（不像现有地理复制的存储系统，其限于少量DC）。这些技术不仅可以通过将数据放置在更靠近用户的位置来减少延迟，而且还可以实现数量级的复制成本降低。此外，该项目将广泛涉及博士，硕士和本科生的研究活动，并从项目的结果将发表在总理的科学会议。为了支持与云计算有关的教育活动，将发行一个“盒装数据中心”工具包。

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.