Flexible Paxos : An Industry Perspective

Paxos is an algorithm for implementing fault-tolerant distributed systems. The core of Paxos is found in many consensus algorithms. Raft and Zab are two prominent protocols that are used in the industry. They serve as the foundation of distributed key-value stores and coordination services such as Consul, Etcd and ZooKeeper. In distributed consensus, the most common way for servers to agree over a value is to use majority quorums. However in 2016, FPaxos (Flexible Paxos) was published. The authors make the observation that majority quorums are not required as intersection is mandatory only across the two phases of Paxos. By taking advantage of this, developers will have more control over the choice between performance and availability. In this paper we will look at how FPaxos can be adopted into existing systems and demonstrate the advantages through a ZooKeeper modification running on City Cloud