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193 lines
5.1 KiB
193 lines
5.1 KiB
package nodes
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import (
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"math/rand"
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"net/rpc"
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"strconv"
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"sync"
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"time"
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"go.uber.org/zap"
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)
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type RequestVoteArgs struct {
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Term int // 候选人的当前任期
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CandidateId string // 候选人 ID
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LastLogIndex int // 候选人最后一条日志的索引
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LastLogTerm int // 候选人最后一条日志的任期
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}
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type RequestVoteReply struct {
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Term int // 当前节点的最新任期
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VoteGranted bool // 是否同意投票
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}
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func (n *Node) startElection() {
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n.mu.Lock()
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defer n.mu.Unlock()
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// 增加当前任期，转换为 Candidate
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n.currTerm++
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n.state = Candidate
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n.votedFor = n.selfId // 自己投自己
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n.storage.SetTermAndVote(n.currTerm, n.votedFor)
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log.Sugar().Infof("[%s] 开始选举，当前任期: %d", n.selfId, n.currTerm)
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// 重新设置选举超时，防止重复选举
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n.resetElectionTimer()
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// 构造 RequestVote 请求
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var lastLogIndex int
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var lastLogTerm int
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if len(n.log) == 0 {
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lastLogIndex = 0
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lastLogTerm = 0 // 论文中定义，空日志时 Term 设为 0
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} else {
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lastLogIndex = len(n.log) - 1
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lastLogTerm = n.log[lastLogIndex].Term
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}
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args := RequestVoteArgs{
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Term: n.currTerm,
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CandidateId: n.selfId,
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LastLogIndex: lastLogIndex,
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LastLogTerm: lastLogTerm,
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}
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// 并行向其他节点发送请求投票
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var mu sync.Mutex
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totalNodes := len(n.nodes)
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grantedVotes := 1 // 自己的票
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for peerId := range n.nodes {
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go func(peerId string) {
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reply := RequestVoteReply{}
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if n.sendRequestVote(peerId, &args, &reply) {
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mu.Lock()
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if reply.Term > n.currTerm {
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// 发现更高任期，回退为 Follower
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log.Sugar().Infof("[%s] 发现更高的 Term (%d)，回退为 Follower", n.selfId, reply.Term)
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n.currTerm = reply.Term
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n.state = Follower
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n.votedFor = ""
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n.storage.SetTermAndVote(n.currTerm, n.votedFor)
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n.resetElectionTimer()
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mu.Unlock()
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return
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}
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if reply.VoteGranted {
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grantedVotes++
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}
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if grantedVotes == totalNodes / 2 + 1 {
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n.state = Leader
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log.Sugar().Infof("[%s] 当选 Leader!", n.selfId)
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n.initLeaderState()
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}
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mu.Unlock()
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}
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}(peerId)
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}
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// 等待选举结果
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time.Sleep(300 * time.Millisecond)
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mu.Lock()
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if n.state == Candidate {
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log.Sugar().Infof("[%s] 选举超时，重新发起选举", n.selfId)
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// n.state = Follower 这里不修改，如果appendentries收到term合理的心跳，再变回follower
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n.resetElectionTimer()
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}
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mu.Unlock()
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}
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func (node *Node) sendRequestVote(peerId string, args *RequestVoteArgs, reply *RequestVoteReply) bool {
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log.Sugar().Infof("[%s] 请求 [%s] 投票给自己", node.selfId, peerId)
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client, err := DialHTTPWithTimeout("tcp", node.nodes[peerId].address)
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if err != nil {
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log.Error("dialing: ", zap.Error(err))
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return false
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}
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defer func(client *rpc.Client) {
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err := client.Close()
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if err != nil {
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log.Error("client close err: ", zap.Error(err))
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}
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}(client)
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callErr := CallWithTimeout(client, "Node.RequestVote", args, reply) // RPC
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if callErr != nil {
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log.Error("dialing node_"+peerId+"fail: ", zap.Error(callErr))
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}
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return callErr == nil
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}
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func (n *Node) RequestVote(args *RequestVoteArgs, reply *RequestVoteReply) error {
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n.mu.Lock()
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defer n.mu.Unlock()
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// 如果候选人的任期小于当前任期，则拒绝投票
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if args.Term < n.currTerm {
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reply.Term = n.currTerm
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reply.VoteGranted = false
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return nil
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}
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// 如果请求的 Term 更高，则更新当前 Term 并回退为 Follower
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if args.Term > n.currTerm {
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n.currTerm = args.Term
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n.state = Follower
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n.votedFor = ""
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n.resetElectionTimer() // 重新设置选举超时
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}
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// 检查是否已经投过票，且是否投给了同一个候选人
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if n.votedFor == "" || n.votedFor == args.CandidateId {
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// 检查日志是否足够新
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var lastLogIndex int
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var lastLogTerm int
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if len(n.log) == 0 {
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lastLogIndex = -1
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lastLogTerm = 0
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} else {
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lastLogIndex = len(n.log) - 1
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lastLogTerm = n.log[lastLogIndex].Term
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}
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if args.LastLogTerm > lastLogTerm ||
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(args.LastLogTerm == lastLogTerm && args.LastLogIndex >= lastLogIndex) {
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// 够新就投票给候选人
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n.votedFor = args.CandidateId
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log.Sugar().Infof("在term(%s), [%s]投票给[%s]", strconv.Itoa(n.currTerm), n.selfId, n.votedFor)
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reply.VoteGranted = true
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n.resetElectionTimer()
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} else {
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reply.VoteGranted = false
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}
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} else {
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reply.VoteGranted = false
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}
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n.storage.SetTermAndVote(n.currTerm, n.votedFor)
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reply.Term = n.currTerm
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return nil
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}
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// follower 500-1000ms内没收到appendentries心跳，就变成candidate发起选举
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func (node *Node) resetElectionTimer() {
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if node.electionTimer == nil {
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node.electionTimer = time.NewTimer(time.Duration(500+rand.Intn(500)) * time.Millisecond)
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go func() {
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for {
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<-node.electionTimer.C
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node.startElection()
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}
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}()
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} else {
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node.electionTimer.Stop()
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node.electionTimer.Reset(time.Duration(500+rand.Intn(500)) * time.Millisecond)
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}
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}
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