/
raft.go
266 lines (222 loc) · 5.54 KB
/
raft.go
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package raft
import (
"strconv"
"time"
log "github.com/sirupsen/logrus"
)
// State represent the current state of a raft node
type State uint32
const (
// FOLLOWER state
FOLLOWER State = iota
// CANDIDATE state
CANDIDATE
// LEADER state
LEADER
// SHUTDOWN state
SHUTDOWN
)
// Raft node
type Raft struct {
state State
listenAddress string
listenTCPPort int
electionTimeOut time.Duration
lastEntry int64
lastVoteTerm uint64
currentTerm uint64
clusterNodes []string
leader string
voteRequestCh chan RequestVoteRequest
votesReceivedCh chan RequestVoteResponse
appendEntriesCh chan AppendEntriesRequest
stopReplicationTask []chan bool
}
func (r *Raft) getNodeID() string {
return r.listenAddress + ":" + strconv.Itoa(r.listenTCPPort)
}
func (r *Raft) setState(state State) {
r.state = state
}
func (r *Raft) getState() State {
return r.state
}
func (r *Raft) setTerm(term uint64) {
r.currentTerm = term
}
func (r *Raft) getTerm() uint64 {
return r.currentTerm
}
func (r *Raft) setLeader(leader string) {
r.leader = leader
}
// GetLeader return leader address
func (r *Raft) GetLeader() string {
return r.leader
}
func (r *Raft) quorum() int {
return len(r.clusterNodes)/2 + 1
}
func (r *Raft) processVoteRequest(req RequestVoteRequest) RequestVoteResponse {
resp := RequestVoteResponse{}
log.Debugf("Procesing vote request: %v", req)
// if the request vote term is longer than the current
// set the node as follower
if r.getTerm() < req.Term {
r.setState(FOLLOWER)
}
// voted already in the current term
// TODO: safty requires to persist the node before, grant a vote, to avoid
// a node that has restarted to vote twice under the same term.
if r.lastVoteTerm >= r.getTerm() {
return resp
}
r.lastVoteTerm = r.getTerm()
resp.Granted = true
return resp
}
func (r *Raft) startReplication() {
replication := func(node string, kill <-chan bool) {
log.Infof("Replicating to node %s", node)
replicationTicker := time.NewTicker(100 * time.Millisecond)
repl := newReplicator(node)
entries := AppendEntriesRequest{
CurrentTerm: r.getTerm(),
LeaderID: r.GetLeader(),
}
for {
select {
case <-replicationTicker.C:
repl.replicate(entries)
case <-kill:
log.Println("Stop replication")
return
}
}
}
i := 0
r.stopReplicationTask = make([]chan bool, len(r.clusterNodes)-1)
for _, node := range r.clusterNodes {
if node == r.getNodeID() {
continue
}
r.stopReplicationTask[i] = make(chan bool)
go replication(node, r.stopReplicationTask[i])
i++
}
}
func (r *Raft) runFollower() {
log.Info("Node in FOLLOWER mode")
heartBeatTimeout := randomTimeout(r.electionTimeOut)
for r.getState() == FOLLOWER {
select {
case req := <-r.voteRequestCh:
req.Response <- r.processVoteRequest(req)
case <-r.votesReceivedCh:
log.Panic("Not expecting a vote reponse at this state")
case entries := <-r.appendEntriesCh:
heartBeatTimeout = randomTimeout(r.electionTimeOut)
r.setLeader(entries.LeaderID)
r.lastEntry = time.Now().UnixNano()
r.setTerm(entries.CurrentTerm)
case <-heartBeatTimeout:
log.Println("Heartbeat timeout")
heartBeatTimeout = randomTimeout(r.electionTimeOut)
r.setState(CANDIDATE)
}
}
}
func (r *Raft) runLeader() {
log.Info("Node in LEADER mode")
r.startReplication()
// terminate replication if the node does hold leadership
defer func() {
for _, task := range r.stopReplicationTask {
task <- true
}
}()
leaderTicker := time.NewTicker(100 * time.Millisecond)
for r.getState() == LEADER {
select {
case req := <-r.voteRequestCh:
req.Response <- r.processVoteRequest(req)
case <-r.votesReceivedCh:
log.Debug("Node retreived a vote but already elected as leader")
case <-leaderTicker.C:
continue
}
}
}
func (r *Raft) runCandidate() {
var voteRequested = false
var receivedVotes = 0
log.Info("Node in CANDIDATE mode")
electionTimer := time.After(1 * time.Second)
//increase term for a new election
r.setTerm(r.getTerm() + 1)
for r.getState() == CANDIDATE {
if !voteRequested {
go r.requestVoteRequest()
voteRequested = true
}
select {
case req := <-r.voteRequestCh:
req.Response <- r.processVoteRequest(req)
case vote := <-r.votesReceivedCh:
if vote.Granted {
receivedVotes++
}
if receivedVotes >= r.quorum() {
r.setState(LEADER)
r.setLeader(r.getNodeID())
log.Infof("Leader elected: %s", r.GetLeader())
}
case <-electionTimer:
log.Debug("Election failed restarting the election")
return
}
}
}
func (r *Raft) runShutdown() {
}
func (r *Raft) runFSM() {
for {
switch r.getState() {
case FOLLOWER:
r.runFollower()
case CANDIDATE:
r.runCandidate()
case LEADER:
r.runLeader()
case SHUTDOWN:
r.runShutdown()
goto DONE
}
}
DONE:
log.Println("Raft FSM stopped")
}
// NewRaft creates a new Raft node
func NewRaft(listenAddress string, listenPort int, clusterNodes []string) *Raft {
raftNode := Raft{
listenTCPPort: listenPort,
listenAddress: listenAddress,
electionTimeOut: 10 * time.Second,
lastEntry: time.Now().UnixNano(),
currentTerm: 1,
clusterNodes: clusterNodes,
voteRequestCh: make(chan RequestVoteRequest),
votesReceivedCh: make(chan RequestVoteResponse),
appendEntriesCh: make(chan AppendEntriesRequest),
lastVoteTerm: 0,
}
// start raft node as follower
raftNode.setState(FOLLOWER)
go raftNode.listen()
go raftNode.runFSM()
return &raftNode
}
// Shutdown terminate a node
func (r *Raft) Shutdown() {
r.setState(SHUTDOWN)
}