Election optimization

[zavier-wong]

• Pre-Vote
• Check Quorum
• Leader Lease

[jovany-wang]

Thanks for the proposals. Maybe it's better to left the details on how we should implement them?

[zavier-wong]

The specific process of the PreVote stage is to send a PreVote message to all nodes before initiating the real election (not much different from the actual voting message, but it will not automatically increase its own term), and the node that receives the message agrees to the conditions for re-election Yes:

1. The term of the PreCandidate node is larger, or the term is the same but the log index is larger;
2. The leader's heartbeat has not been received within at least one election timeout period;

Only when more than half of the nodes agree to PreVote, the node can self-increase the term to initiate a real election and send a RequestVote request.

[zavier-wong]

Check Quorum is a mechanism for leaders to step down. The leader node sends a message to check whether it maintains more than half of the connections with other nodes in the cluster. If not, it becomes a follower node.

[zavier-wong]

The leader lease mechanism means that the node will not vote for other nodes within an election timeout period when the node receives a message from the leader.