分布式协议

//zookeeper zab
角色: leader,follower,observer(观察者)
关键字:
zxid -> (epoch,counter)
sid -> serverId

//raft
角色: leader,follower,candidate(候选人)
关键字:
RequestVoteRequest -> (term,lastLogIndex)
election timeout
heartbeat timeout

//法定人数
this.quorum = this.peers.size() / 2 + 1;