Raft phd thesis

The Verdi team at the University of Washington has completed a machine-checked proof of safety for the basic Raft algorithm in Coq. See the press release. There have been a few minor updates to the TLA+ specification: https://github.com/ongardie/raft.tla.

Raft first elects a server as leader, then concentrates all decision-making onto the leader. These two basic steps are relatively independent and form a better structure than Paxos, whose components are hard to separate. Raft elects a leader using voting and randomized timeouts.

Raft is also more suitable than previous algorithms for real-world implementations. It performs well enough for practical deployments, and it addresses all aspects of building a complete system, including how to manage client interactions, how to change the cluster membership, and how to compact the log when it grows too large.

Raft leverages a simple invariant on how logs grow to reduce the algorithm’s state space and accomplish this task with minimal mechanism. Raft is also more suitable than previous algorithms for real-world implementations.