CSR-PDOS: Availability-Aware Services

由于分布式系统是跨机器部署的，可以在任何时候自由选择加入或退出，因此主机可用性是一个首要问题。系统通常以反应式的方式处理可用性，对具有不同可用性行为的机器几乎没有区别。简而言之，当前的系统将波动的可用性视为一个问题。 这个项目通过预测一个更大的集体中许多单个主机的可用性，将可用性视为一个机会。通过使用预测器的竞争性锦标赛，该项目能够预测许多节点的可用性，即使在完全未管理的网络中。研究工作将这些预测因素应用于三个领域。 在第一，流行病传播，该项目增加了目前的病毒感染模型，除了拓扑结构考虑可用性。 第二个应用是延迟容忍网络。 通过使用可用性预测作为实际的联系预言，可以改善端到端延迟和路由效率。 作为第三个应用，该项目将可用性预测应用于基于DHT的存储和归档网络。 通过将一些副本偏向高可用节点，减少了由扰动引起的文档传输，并提高了整体系统的可用性。 通过将维护协议与可用性预测相结合，进一步降低了网络开销。

As distributed systems are deployed across machines free to opt in or out at any time, host availability is a first-order concern. Systems typically deal with availability in a reactive way, making little distinction between machines with different availability behaviors. In short, current systems view fluctuating availability as a problem. This project views availability as an opportunity, by predicting the availability of many individual hosts in a larger collective. By using a competitive tournament of predictors, the project is able to predict the availability of many nodes even in completely unmanaged networks. The research effort applies these predictors in three domains. In the first, epidemic propagation, the project augments current viral infection models to consider availability in addition to topology. The second application is delay-tolerant networking. By using availability prediction as a practical contact oracle, one can improve end-to-end latency and routing efficiency. As a third application, the project applies availability prediction to DHT-based storage and archival networks. By biasing placement of some replicas towards highly available nodes, churn-induced document transfer is reduced and overall system availability improved. By ugmenting the maintenance protocols with availability predictions, network overhead is further reduced.