hashicorp/raft模块实现的raft集群存在节点跨集群身份冲突问题

我通过模块github.com/hashicorp/raft使用golang实现了一个raft集群功能，发现如下场景中会遇到一个问题：

测试启动如下2个raft集群，集群名称，和集群node与IP地址如下，raft集群均通过BootstrapCluster方法初始化：

Cluster1 BootstrapCluster servers:

- node1: {raft.ServerID: c1-node1, raft.ServerAddress: 192.168.100.1:7000}

- node2: {raft.ServerID: c1-node2, raft.ServerAddress: 192.168.100.2:7000}

- node3: {raft.ServerID: c1-node3, raft.ServerAddress: 192.168.100.3:7000}

Cluster2 BootstrapCluster servers：

- node3: {raft.ServerID: c2-node3, raft.ServerAddress: 192.168.100.3:7000}

- node4: {raft.ServerID: c2-node4, raft.ServerAddress: 192.168.100.4:7000}

- node5: {raft.ServerID: c2-node5, raft.ServerAddress: 192.168.100.5:7000}

其中，"node3"的地址会存在2个集群中。

1. "node1","node2"按照"Cluster1"启动:

sudo ./raft_svr -cluster 'c1-node1,127.0.0.1,800;c1-node2,127.0.0.2,800;c1-node3,127.0.0.3,800' -id c1-node1

sudo ./raft_svr -cluster 'c1-node1,127.0.0.1,800;c1-node2,127.0.0.2,800;c1-node3,127.0.0.3,800' -id c1-node2

1. "node3","node4","node5"先按照"Cluster2"启动:

sudo ./raft_svr -cluster 'c2-node3,127.0.0.3,800;c2-node4,127.0.0.4,800;c2-node5,127.0.0.5,800' -id c2-node3

sudo ./raft_svr -cluster 'c2-node3,127.0.0.3,800;c2-node4,127.0.0.4,800;c2-node5,127.0.0.5,800' -id c2-node4

sudo ./raft_svr -cluster 'c2-node3,127.0.0.3,800;c2-node4,127.0.0.4,800;c2-node5,127.0.0.5,800' -id c2-node5

然后就会发现"node3"会在"Cluster1"和"Cluster2"之间来回切换，一会属于"Cluster1"，一会属于"Cluster2".

INFO[0170] current state:Follower, leader address:127.0.0.5:800, servers:[{Suffrage:Voter ID:c2-node3 Address:127.0.0.3:800} {Suffrage:Voter ID:c2-node4 Address:127.0.0.4:800} {Suffrage:Voter ID:c2-node5 Address:127.0.0.5:800}], last contact:2025-05-14 15:35:53.330867 +0800 CST m=+169.779019126
INFO[0171] current state:Follower, leader address:127.0.0.1:800, servers:[{Suffrage:Voter ID:c2-node3 Address:127.0.0.3:800} {Suffrage:Voter ID:c2-node4 Address:127.0.0.4:800} {Suffrage:Voter ID:c2-node5 Address:127.0.0.5:800}], last contact:2025-05-14 15:35:54.308388 +0800 CST m=+170.756576126

我的代码如下:

package main

import (
	"flag"
	"fmt"
	"io"
	"net"
	"os"
	"strconv"
	"strings"
	"time"

	"github.com/hashicorp/raft"
	log "github.com/sirupsen/logrus"
)

type raftCluster struct {
	localRaftID     raft.ServerID
	servers         map[raft.ServerID]raft.ServerAddress // raftID : raftAddressPort
	raft            *raft.Raft
	electionTimeout time.Duration
}

func (r *raftCluster) Start() error {
	config := raft.DefaultConfig()
	config.HeartbeatTimeout = 2000 * time.Millisecond
	config.ElectionTimeout = 5000 * time.Millisecond
	config.CommitTimeout = 2000 * time.Millisecond
	config.LeaderLeaseTimeout = 2000 * time.Millisecond
	config.LocalID = r.localRaftID
	config.LogOutput = log.StandardLogger().Out

	r.electionTimeout = config.ElectionTimeout * time.Duration(len(r.servers)*2)

	localAddressPort := string(r.servers[r.localRaftID])
	tcpAddr, err := net.ResolveTCPAddr("tcp", localAddressPort)
	if err != nil {
		return fmt.Errorf("resolve tcp address %s, %v", localAddressPort, err)
	}
	transport, err := raft.NewTCPTransport(localAddressPort, tcpAddr, 2, 10*time.Second, log.StandardLogger().Out)
	if err != nil {
		return fmt.Errorf("fail to create tcp transport, localAddressPort:%s, tcpAddr:%v, %v",
			localAddressPort, tcpAddr, err)
	}
	snapshots := raft.NewInmemSnapshotStore()
	logStore := raft.NewInmemStore()
	stableStore := raft.NewInmemStore()
	fm := NewFsm()
	r.raft, err = raft.NewRaft(config, fm, logStore, stableStore, snapshots, transport)
	if err != nil {
		return fmt.Errorf("create raft error, %v", err)
	}

	var configuration raft.Configuration
	for sID, addr := range r.servers {
		server := raft.Server{
			ID:      sID,
			Address: addr,
		}
		configuration.Servers = append(configuration.Servers, server)
	}
	err = r.raft.BootstrapCluster(configuration).Error()
	if err != nil {
		return fmt.Errorf("raft bootstrap faild, conf:%v, %v", configuration, err)
	}
	log.Infof("bootstrap cluster as config: %v", configuration)

	return nil
}

func (r *raftCluster) checkLeaderState() {
	ticker := time.NewTicker(time.Second)
	for {
		select {
		case leader := <-r.raft.LeaderCh():
			log.Infof("im leader:%v, state:%s, leader address:%s", leader, r.raft.State(), r.raft.Leader())

		case <-ticker.C:
			verifyErr := r.raft.VerifyLeader().Error()
			servers := r.raft.GetConfiguration().Configuration().Servers
			switch verifyErr {
			case nil:
				log.Infof("im leader, servers:%v", servers)
			case raft.ErrNotLeader:
				// check cluster leader
				log.Infof("current state:%v, servers:%+v, leader address:%v, last contact:%v",
					r.raft.State(), servers, r.raft.Leader(), r.raft.LastContact())
			}
		}
	}
}

func main() {
	var (
		clusters = flag.String("cluster", "",
			"cluster node address, fmt: ID,IP,Port;ID,IP,Port")
		clusterId = flag.String("id", "", "cluster id")
	)
	flag.Parse()

	if *clusterId == "" {
		log.Infof("cluster id messing")
		os.Exit(1)
	}

	servers := make(map[raft.ServerID]raft.ServerAddress)
	for _, cluster := range strings.Split(*clusters, ";") {
		info := strings.Split(cluster, ",")
		var (
			nid   string
			nip   net.IP
			nport int
			err   error
		)
		switch {
		case len(info) == 3:
			nid = info[0]
			nip = net.ParseIP(info[1])
			if nip == nil {
				log.Infof("cluster %s ip %s parse failed", cluster, info[1])
				os.Exit(1)
			}
			nport, err = strconv.Atoi(info[2])
			if err != nil {
				log.Infof("cluster %s port %s parse failed, %v", cluster, info[2], err)
			}
		default:
			log.Infof("cluster args value is bad format")
			os.Exit(1)
		}
		log.Infof("cluster node id:%s, ip:%v, port:%d", nid, nip, nport)
		addr := net.TCPAddr{IP: nip, Port: nport}
		servers[raft.ServerID(nid)] = raft.ServerAddress(addr.String())
	}

	r := raftCluster{
		localRaftID: raft.ServerID(*clusterId),
		servers:     servers,
	}
	err := r.Start()
	if err != nil {
		log.Infof("rafter cluster start failed, %v", err)
		os.Exit(1)
	}
	r.checkLeaderState()
}

// SimpleFsm: 实现一个简单的Fsm

type SimpleFsm struct {
	db database
}

func NewFsm() *SimpleFsm {
	fsm := &SimpleFsm{
		db: NewDatabase(),
	}
	return fsm
}

func (f *SimpleFsm) Apply(l *raft.Log) interface{} {
	return nil
}

func (f *SimpleFsm) Snapshot() (raft.FSMSnapshot, error) {
	return &f.db, nil
}

func (f *SimpleFsm) Restore(io.ReadCloser) error {
	return nil
}

type database struct{}

func NewDatabase() database {
	return database{}
}

func (d *database) Get(key string) string {
	return "not implemented"
}

func (d *database) Set(key, value string) {}

func (d *database) Persist(sink raft.SnapshotSink) error {
	_, _ = sink.Write([]byte{})
	_ = sink.Close()
	return nil
}

func (d *database) Release() {}

测试了hashicorp/raft多个版本都是相同的情况，以当前最新版本v1.7.3分析了下，应该是如下原因导致的：

1. 集群启动后各个节点都通过BootstrapCluster初始化，并引导集群选举，在node3上可以看见如下日志，说明在选举阶段node3能判断自己不属于Cluster1集群。

[WARN]  raft: rejecting appendEntries request since node is not in configuration: from=c1-node1

1. 但是当Cluster1选举出leader后，node3就可能变成Cluster的成员了，这是因为Cluster1的leader会不断通过心跳向集群内node发送日志，而在这个过程中：
   1. fllower节点是不会判断这个请求的leader是否是自己集群中的设备。
   2. fllower节点只对比请求日志的编号是否比自己本地的大，如果比本地的大，就接收存下来，并将发起请求的leader设置为自己集群的leader。
   3. 同样的，在Cluster2选举出leader后，Cluster2的leader也会向node3不断通过心跳发送日志请求。这就导致node3一会属于Cluster1，一会属于Cluster2

这个过程中的漏洞出在raft节点接收日志修改leader的过程，代码位置为hashicop/raft模块中的raft.go:L1440位置的func (r *Raft) appendEntries(rpc RPC, a *AppendEntriesRequest)函数

修改改函数，增加对请求Leader的ID的判断，则可避免这个问题：

	// Ignore an older term
	if a.Term < r.getCurrentTerm() {
		return
	}

	// yzc add，这里是我们添加的函数，注意，拒绝之后需要返回错误，否则会导致另外一个集群不断重新选举
	if len(r.configurations.latest.Servers) > 0 && !inConfiguration(r.configurations.latest, ServerID(a.ID)) {
		r.logger.Warn("rejecting appendEntries request since node is not in configuration",
			"from", ServerID(a.ID))
		rpcErr = fmt.Errorf("node is not in configuration")
		return
	}

	// Increase the term if we see a newer one, also transition to follower
	// if we ever get an appendEntries call
	if a.Term > r.getCurrentTerm() || (r.getState() != Follower && !r.candidateFromLeadershipTransfer.Load()) {
		// Ensure transition to follower
		r.setState(Follower)
		r.setCurrentTerm(a.Term)
		resp.Term = a.Term
	}

重新编译运行后，我们看到node3始终保持在Cluster2中，并且可以看到如下日志

[WARN]  raft: rejecting appendEntries request since node is not in configuration: from=c1-node1

在Cluster1的leader日志中，我们可以看到该leader向node3发送心跳失败的日志：

[DEBUG] raft: failed to contact: server-id=c1-node3 time=1m29.121143167s
[ERROR] raft: failed to heartbeat to: peer=127.0.0.3:800 backoff time=1s error="node is not in configuration"