NetRS: Cutting Response Latency in Distributed Key-Value Stores with In-Network Replica Selection

In distributed key-value stores, performance fluctuations generally occur across servers, especially when the servers are deployed in a cloud environment. Hence, the replica selected for a request will directly affect the response latency. In the context of key-value stores, even the state-of-the-art algorithm of replica selection still has considerable room for improving the response latency. In this paper, we present the fundamental factors that prevent replica selection algorithms from being effective. We address these factors by proposing NetRS, a framework that enables in-network replica selection for key-value stores. NetRS exploits emerging network devices, including programmable switches and network accelerators, to select replicas for requests. NetRS supports diverse algorithms of replica selection and is suited to the network topology of modern data centers. Compared with the conventional scheme of clients selecting replicas for requests, NetRS could effectively cut the response latency according to our extensive evaluations. Specifically, NetRS reduces the average latency by up to 48.4%, and the 99th latency by up to 68.7%.