Raft Consensus

Overview

Raft manages a replicated log by separating leader election, log replication, and safety. A leader accepts commands, appends entries, sends them to followers, and commits after majority acknowledgement under the algorithm’s term rules.

If the leader fails, followers hold an election and a new leader with an eligible log can continue. Raft tolerates crashes and partitions while preserving consistency, but it does not tolerate arbitrary malicious behavior by authenticated members. Raft is common in databases, coordination services, and permissioned infrastructure rather than open adversarial blockchain consensus. Deployments must configure quorum, membership changes, durable storage, election timeouts, and snapshot recovery correctly. Majority availability is required for progress, and a three-node cluster tolerates only one unavailable node.

Recovery plans must reflect whether the design halts to preserve safety, permits temporary reorganization, or relies on social or governance intervention after exceptional failure. Operations teams should monitor chain progress, competing branches, participation, and protocol-specific fault indicators. Technical review should examine the full decision process: who may propose data, how other participants validate it, how competing histories are ranked, and what evidence makes an outcome difficult or impossible to reverse. A mechanism’s label does not define those details across every implementation.

Safety, liveness, and accountability should be assessed separately under partitions and coordinated failures. Protocol safety depends on the resource or authority used to influence consensus, participant concentration, network timing, client behavior, and the cost of equivocation, censorship, or history revision. Practical implication: Raft provides understandable majority-based log replication for crash faults, not Byzantine security against malicious participating servers.