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In the context of Raft, it is a very common for leaders to hit network partition. We implemented the progress timeout in KIP-595, so that when a majority of voters are not fetching from the leader, the current leader will start election to reach out to other followers to re-establish the leadership or learn about the new leader. However, if the zombie leader could not connect to the quorum for long enough, it will timeout and start election, while bumping its epoch. Until it eventually reconnects to the quorum, the zombie leader will repeatedly bump its epoch due to election time out. The consequence is that the zombie leader will gain a much higher epoch than other voters inside the quorum and win the election, introducing extra unavailability time. During quorum reassignment, the removed voters could also try to start election to ask active leader to step down which affects the ongoing transition. This is called "disruptive server" the Raft literature. Furthermore, the rapid bumping of the epoch increases the chance of epoch overflow, which is very dangerous in the Kafka Raft as we have been using uint32 for epoch due to historical message formats, compared with using uint64.

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