Raft (algorithm): Difference between revisions

Revision as of 20:55, 9 September 2017

Revision as of 15:36, 11 September 2017

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==== State Machine Safety ====

This rule is ensured by a simple restriction: a candidate can't win an election unless itits logslog contains all committed entries. In order to be elected, a candidate has to contact a majority of the cluster, and givens the rules for logs to be committed, it means that every committed entry is going to be present on at least one of the servers the candidate contact.

Raft determines which of two logs (carried by two distinct servers) is more up-to-date by comparing the index term of the last entries in the logs. If the logs have last entry with different terms, then the log with the later term is more up-to-date. If the logs end with the same term, then whichever log is longer is more up-to-date.