Raft's Safety, Fault-Tolerance, and Availability Protocols

Let's learn how Raft ensures safety, handles leader and followers' crashes, and maintains availability.


The previous lessons discussed how Raft selects leaders and replicates log entries. Still, additional mechanisms are needed to guarantee that every state machine executes the same commands in the same order. To see why this is the case, take an example of a follower that misses several log entries while the leader commits them. Such a follower can become the new leader and can overwrite the committed entries with new ones, resulting in different state machines executing different sequences of commands. The following slides show such a scenario:

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