Engage: Session Guarantees for the Edge

Edge computing offers support for latencyconstrained applications, by replicating data in the edge. Edge storage systems need to adopt both partial replication, as only data of interest needs to be replicated, and weak consistency models, to avoid the overhead and latency induced by the coordination mechanisms of strong consistency models. In this context, session guarantees are a powerful tool that can be used to simplify the design of edge applications. This paper presents Engage, a storage system that offers efficient support for session guarantees in a partially replicated edge setting. To achieve this, Engage combines the use of vector clocks and distributed metadata propagation services with a payload propagation scheme tailored for the edge. We have implemented Engage and evaluated its performance experimentally. The results show that, when compared with previous proposals, the combination of techniques employed by Engage reduce both the number of false dependencies, that can slow down the system, and the signaling overhead, while improving the freshness of data exposed to clients.