Pirogue, a lighter dynamic version of the Raft distributed consensus algorithm

摘要

Raft is a new distributed consensus algorithm that is easier to understand than the older Paxos algorithm. Raft's major drawback is its high energy footprint: as it relies on static quorums for deciding when it can commit updates, it requires five participants to protect against two simultaneous failures. We propose to reduce this footprint by replacing the static quorums that Raft currently uses by quorums that vary according to the number of currently available participants. We present first a modified dynamic-linear voting protocol that disables single-server updates and show that a Raft cluster with four participants managed by this protocol would be almost as available as a conventional Raft cluster with five participants and always tolerate the irrecoverable failure of any single participant without any data loss. In addition, we show a Raft cluster with three participants and a witness managed by an unmodified dynamic-linear voting protocol would be more available than a conventional Raft cluster with five participants and could still tolerate most irrecoverable failures of any single participant while maintaining recoverability.