This rule is ensured by a simple restriction: a candidate can't win an election unless its log contains all committed entries. In order to be elected, a candidate has to contact a majority of the cluster, and given 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 candidates 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 a 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.
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== Production use of Raft ==
* [[CockroachDB|CockroachDB]] uses Raft in the Replication Layer.<ref>{{Cite web |title=Replication Layer {{!}} CockroachDB Docs |url=https://www.cockroachlabs.com/docs/stable/architecture/replication-layer.html |access-date=2022-06-21 |website=www.cockroachlabs.com}}</ref>
* [[etcd|Etcd]] uses Raft to manage a highly-available replicated log <ref>{{Cite web |title=Raft README |url= https://github.com/etcd-io/etcd/blob/main/raft/README.md |access-date=2022-08-25|website=github.com}}</ref>
* [[MongoDB|MongoDB]] uses a variant of Raft in the replication set.
* [[Splunk|Splunk]] Enterprise uses Raft in a Search Head Cluster (SHC) <ref>{{Cite web |date=2022-08-24| title= Handle Raft issues|url=https://docs.splunk.com/Documentation/Splunk/9.0.0/DistSearch/Handleraftissues| access-date=2022-08-24|website=Splunk |language=en-US}}</ref>
* [[TiDB|TiDB]] uses Raft the storage engine TiKV.<ref>{{Cite web |date=2021-09-01 |title=Raft and High Availability |url=https://en.pingcap.com/blog/raft-and-high-availability/ |access-date=2022-06-21 |website=PingCAP |language=en-US}}</ref>
* [[YugabyteDB|YugabyteDB]] uses Raft in the DocDB Replication <ref>{{Cite web |title=Replication {{!}} YugabyteDB Docs |url=https://docs.yugabyte.com/preview/architecture/docdb-replication/replication/ |access-date=2022-08-19|website=www.yugabyte.com}}</ref>
