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raft

Raft?​

ABSTRACT

⛵ Raft is a distributed consensus algorithm designed to ensure that multiple nodes agree on the same state, even in the presence of failures.

  • etcd uses Raft internally to synchronize data across replicas.

Key Goals​

  • Consistency: All healthy nodes agree on the same log of updates.
  • Fault tolerance: System works even if some nodes fail.
  • Leader-based design: One leader handles all writes; followers replicate the log.

How Raft Works (Simplified)​

three core mechanisms

Leader Election​

  • When a cluster starts or the leader dies:
    1. Nodes vote for a leader.
    2. A node becomes leader if it gets majority votes.
    3. Leader handles all writes.

Log Replication​

  • Leader receives a write request, appends it to its log.
  • Sends AppendEntries RPCs to followers.
  • Once majority of followers acknowledge, the leader commits the entry.

Safety & Consistency​

  • Raft guarantees that committed entries are never lost.
  • Even if the leader crashes, the new leader has the latest committed log.

References

  • ChatGPT