Question

Which consensus algorithm uses term numbers to ensure that only a node with the most up-to-date log can be elected as the cluster leader?

Accepted Answer

The consensus algorithm that uses term numbers to ensure that only a node with the most up-to-date log can be elected as the cluster leader is Raft. In Raft, a term number is a logical clock used to detect obsolete information; it acts as a monotonically increasing integer that segments time into periods of leadership. During an election, a candidate must include information about its log in its request to other nodes. This information consists of the index and the term of the last log entry stored by the candidate. When a follower receives a RequestVote message, it compares the candidate&#x27;s log to its own. The follower denies the vote if its own log is more up-to-date, which occurs if the follower&#x27;s last log entry has a higher term number or, if the terms are equal, a higher index. By requiring a candidate to receive votes from a majority of the cluster, Raft guarantees that the elected leader contains all committed entries from previous terms, as any committed entry must exist on at least a majority of nodes, and at least one node in that majority will inevitably have a log that is as up-to-date as any other node, thereby preventing an outdated node from gaining the necessary consensus to become leader.

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Which consensus algorithm uses term numbers to ensure that only a node with the most up-to-date log can be elected as the cluster leader?

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