[VOL-2538] Logging - Implement dynamic log levels in ofagent
Change-Id: I9582230d9d3c34ea84339fddf2b2f3b3d2804808
diff --git a/vendor/go.etcd.io/etcd/raft/raft.go b/vendor/go.etcd.io/etcd/raft/raft.go
new file mode 100644
index 0000000..cdcb43d
--- /dev/null
+++ b/vendor/go.etcd.io/etcd/raft/raft.go
@@ -0,0 +1,1656 @@
+// Copyright 2015 The etcd Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package raft
+
+import (
+ "bytes"
+ "errors"
+ "fmt"
+ "math"
+ "math/rand"
+ "sort"
+ "strings"
+ "sync"
+ "time"
+
+ "go.etcd.io/etcd/raft/confchange"
+ "go.etcd.io/etcd/raft/quorum"
+ pb "go.etcd.io/etcd/raft/raftpb"
+ "go.etcd.io/etcd/raft/tracker"
+)
+
+// None is a placeholder node ID used when there is no leader.
+const None uint64 = 0
+const noLimit = math.MaxUint64
+
+// Possible values for StateType.
+const (
+ StateFollower StateType = iota
+ StateCandidate
+ StateLeader
+ StatePreCandidate
+ numStates
+)
+
+type ReadOnlyOption int
+
+const (
+ // ReadOnlySafe guarantees the linearizability of the read only request by
+ // communicating with the quorum. It is the default and suggested option.
+ ReadOnlySafe ReadOnlyOption = iota
+ // ReadOnlyLeaseBased ensures linearizability of the read only request by
+ // relying on the leader lease. It can be affected by clock drift.
+ // If the clock drift is unbounded, leader might keep the lease longer than it
+ // should (clock can move backward/pause without any bound). ReadIndex is not safe
+ // in that case.
+ ReadOnlyLeaseBased
+)
+
+// Possible values for CampaignType
+const (
+ // campaignPreElection represents the first phase of a normal election when
+ // Config.PreVote is true.
+ campaignPreElection CampaignType = "CampaignPreElection"
+ // campaignElection represents a normal (time-based) election (the second phase
+ // of the election when Config.PreVote is true).
+ campaignElection CampaignType = "CampaignElection"
+ // campaignTransfer represents the type of leader transfer
+ campaignTransfer CampaignType = "CampaignTransfer"
+)
+
+// ErrProposalDropped is returned when the proposal is ignored by some cases,
+// so that the proposer can be notified and fail fast.
+var ErrProposalDropped = errors.New("raft proposal dropped")
+
+// lockedRand is a small wrapper around rand.Rand to provide
+// synchronization among multiple raft groups. Only the methods needed
+// by the code are exposed (e.g. Intn).
+type lockedRand struct {
+ mu sync.Mutex
+ rand *rand.Rand
+}
+
+func (r *lockedRand) Intn(n int) int {
+ r.mu.Lock()
+ v := r.rand.Intn(n)
+ r.mu.Unlock()
+ return v
+}
+
+var globalRand = &lockedRand{
+ rand: rand.New(rand.NewSource(time.Now().UnixNano())),
+}
+
+// CampaignType represents the type of campaigning
+// the reason we use the type of string instead of uint64
+// is because it's simpler to compare and fill in raft entries
+type CampaignType string
+
+// StateType represents the role of a node in a cluster.
+type StateType uint64
+
+var stmap = [...]string{
+ "StateFollower",
+ "StateCandidate",
+ "StateLeader",
+ "StatePreCandidate",
+}
+
+func (st StateType) String() string {
+ return stmap[uint64(st)]
+}
+
+// Config contains the parameters to start a raft.
+type Config struct {
+ // ID is the identity of the local raft. ID cannot be 0.
+ ID uint64
+
+ // peers contains the IDs of all nodes (including self) in the raft cluster. It
+ // should only be set when starting a new raft cluster. Restarting raft from
+ // previous configuration will panic if peers is set. peer is private and only
+ // used for testing right now.
+ peers []uint64
+
+ // learners contains the IDs of all learner nodes (including self if the
+ // local node is a learner) in the raft cluster. learners only receives
+ // entries from the leader node. It does not vote or promote itself.
+ learners []uint64
+
+ // ElectionTick is the number of Node.Tick invocations that must pass between
+ // elections. That is, if a follower does not receive any message from the
+ // leader of current term before ElectionTick has elapsed, it will become
+ // candidate and start an election. ElectionTick must be greater than
+ // HeartbeatTick. We suggest ElectionTick = 10 * HeartbeatTick to avoid
+ // unnecessary leader switching.
+ ElectionTick int
+ // HeartbeatTick is the number of Node.Tick invocations that must pass between
+ // heartbeats. That is, a leader sends heartbeat messages to maintain its
+ // leadership every HeartbeatTick ticks.
+ HeartbeatTick int
+
+ // Storage is the storage for raft. raft generates entries and states to be
+ // stored in storage. raft reads the persisted entries and states out of
+ // Storage when it needs. raft reads out the previous state and configuration
+ // out of storage when restarting.
+ Storage Storage
+ // Applied is the last applied index. It should only be set when restarting
+ // raft. raft will not return entries to the application smaller or equal to
+ // Applied. If Applied is unset when restarting, raft might return previous
+ // applied entries. This is a very application dependent configuration.
+ Applied uint64
+
+ // MaxSizePerMsg limits the max byte size of each append message. Smaller
+ // value lowers the raft recovery cost(initial probing and message lost
+ // during normal operation). On the other side, it might affect the
+ // throughput during normal replication. Note: math.MaxUint64 for unlimited,
+ // 0 for at most one entry per message.
+ MaxSizePerMsg uint64
+ // MaxCommittedSizePerReady limits the size of the committed entries which
+ // can be applied.
+ MaxCommittedSizePerReady uint64
+ // MaxUncommittedEntriesSize limits the aggregate byte size of the
+ // uncommitted entries that may be appended to a leader's log. Once this
+ // limit is exceeded, proposals will begin to return ErrProposalDropped
+ // errors. Note: 0 for no limit.
+ MaxUncommittedEntriesSize uint64
+ // MaxInflightMsgs limits the max number of in-flight append messages during
+ // optimistic replication phase. The application transportation layer usually
+ // has its own sending buffer over TCP/UDP. Setting MaxInflightMsgs to avoid
+ // overflowing that sending buffer. TODO (xiangli): feedback to application to
+ // limit the proposal rate?
+ MaxInflightMsgs int
+
+ // CheckQuorum specifies if the leader should check quorum activity. Leader
+ // steps down when quorum is not active for an electionTimeout.
+ CheckQuorum bool
+
+ // PreVote enables the Pre-Vote algorithm described in raft thesis section
+ // 9.6. This prevents disruption when a node that has been partitioned away
+ // rejoins the cluster.
+ PreVote bool
+
+ // ReadOnlyOption specifies how the read only request is processed.
+ //
+ // ReadOnlySafe guarantees the linearizability of the read only request by
+ // communicating with the quorum. It is the default and suggested option.
+ //
+ // ReadOnlyLeaseBased ensures linearizability of the read only request by
+ // relying on the leader lease. It can be affected by clock drift.
+ // If the clock drift is unbounded, leader might keep the lease longer than it
+ // should (clock can move backward/pause without any bound). ReadIndex is not safe
+ // in that case.
+ // CheckQuorum MUST be enabled if ReadOnlyOption is ReadOnlyLeaseBased.
+ ReadOnlyOption ReadOnlyOption
+
+ // Logger is the logger used for raft log. For multinode which can host
+ // multiple raft group, each raft group can have its own logger
+ Logger Logger
+
+ // DisableProposalForwarding set to true means that followers will drop
+ // proposals, rather than forwarding them to the leader. One use case for
+ // this feature would be in a situation where the Raft leader is used to
+ // compute the data of a proposal, for example, adding a timestamp from a
+ // hybrid logical clock to data in a monotonically increasing way. Forwarding
+ // should be disabled to prevent a follower with an inaccurate hybrid
+ // logical clock from assigning the timestamp and then forwarding the data
+ // to the leader.
+ DisableProposalForwarding bool
+}
+
+func (c *Config) validate() error {
+ if c.ID == None {
+ return errors.New("cannot use none as id")
+ }
+
+ if c.HeartbeatTick <= 0 {
+ return errors.New("heartbeat tick must be greater than 0")
+ }
+
+ if c.ElectionTick <= c.HeartbeatTick {
+ return errors.New("election tick must be greater than heartbeat tick")
+ }
+
+ if c.Storage == nil {
+ return errors.New("storage cannot be nil")
+ }
+
+ if c.MaxUncommittedEntriesSize == 0 {
+ c.MaxUncommittedEntriesSize = noLimit
+ }
+
+ // default MaxCommittedSizePerReady to MaxSizePerMsg because they were
+ // previously the same parameter.
+ if c.MaxCommittedSizePerReady == 0 {
+ c.MaxCommittedSizePerReady = c.MaxSizePerMsg
+ }
+
+ if c.MaxInflightMsgs <= 0 {
+ return errors.New("max inflight messages must be greater than 0")
+ }
+
+ if c.Logger == nil {
+ c.Logger = raftLogger
+ }
+
+ if c.ReadOnlyOption == ReadOnlyLeaseBased && !c.CheckQuorum {
+ return errors.New("CheckQuorum must be enabled when ReadOnlyOption is ReadOnlyLeaseBased")
+ }
+
+ return nil
+}
+
+type raft struct {
+ id uint64
+
+ Term uint64
+ Vote uint64
+
+ readStates []ReadState
+
+ // the log
+ raftLog *raftLog
+
+ maxMsgSize uint64
+ maxUncommittedSize uint64
+ // TODO(tbg): rename to trk.
+ prs tracker.ProgressTracker
+
+ state StateType
+
+ // isLearner is true if the local raft node is a learner.
+ isLearner bool
+
+ msgs []pb.Message
+
+ // the leader id
+ lead uint64
+ // leadTransferee is id of the leader transfer target when its value is not zero.
+ // Follow the procedure defined in raft thesis 3.10.
+ leadTransferee uint64
+ // Only one conf change may be pending (in the log, but not yet
+ // applied) at a time. This is enforced via pendingConfIndex, which
+ // is set to a value >= the log index of the latest pending
+ // configuration change (if any). Config changes are only allowed to
+ // be proposed if the leader's applied index is greater than this
+ // value.
+ pendingConfIndex uint64
+ // an estimate of the size of the uncommitted tail of the Raft log. Used to
+ // prevent unbounded log growth. Only maintained by the leader. Reset on
+ // term changes.
+ uncommittedSize uint64
+
+ readOnly *readOnly
+
+ // number of ticks since it reached last electionTimeout when it is leader
+ // or candidate.
+ // number of ticks since it reached last electionTimeout or received a
+ // valid message from current leader when it is a follower.
+ electionElapsed int
+
+ // number of ticks since it reached last heartbeatTimeout.
+ // only leader keeps heartbeatElapsed.
+ heartbeatElapsed int
+
+ checkQuorum bool
+ preVote bool
+
+ heartbeatTimeout int
+ electionTimeout int
+ // randomizedElectionTimeout is a random number between
+ // [electiontimeout, 2 * electiontimeout - 1]. It gets reset
+ // when raft changes its state to follower or candidate.
+ randomizedElectionTimeout int
+ disableProposalForwarding bool
+
+ tick func()
+ step stepFunc
+
+ logger Logger
+}
+
+func newRaft(c *Config) *raft {
+ if err := c.validate(); err != nil {
+ panic(err.Error())
+ }
+ raftlog := newLogWithSize(c.Storage, c.Logger, c.MaxCommittedSizePerReady)
+ hs, cs, err := c.Storage.InitialState()
+ if err != nil {
+ panic(err) // TODO(bdarnell)
+ }
+
+ if len(c.peers) > 0 || len(c.learners) > 0 {
+ if len(cs.Voters) > 0 || len(cs.Learners) > 0 {
+ // TODO(bdarnell): the peers argument is always nil except in
+ // tests; the argument should be removed and these tests should be
+ // updated to specify their nodes through a snapshot.
+ panic("cannot specify both newRaft(peers, learners) and ConfState.(Voters, Learners)")
+ }
+ cs.Voters = c.peers
+ cs.Learners = c.learners
+ }
+
+ r := &raft{
+ id: c.ID,
+ lead: None,
+ isLearner: false,
+ raftLog: raftlog,
+ maxMsgSize: c.MaxSizePerMsg,
+ maxUncommittedSize: c.MaxUncommittedEntriesSize,
+ prs: tracker.MakeProgressTracker(c.MaxInflightMsgs),
+ electionTimeout: c.ElectionTick,
+ heartbeatTimeout: c.HeartbeatTick,
+ logger: c.Logger,
+ checkQuorum: c.CheckQuorum,
+ preVote: c.PreVote,
+ readOnly: newReadOnly(c.ReadOnlyOption),
+ disableProposalForwarding: c.DisableProposalForwarding,
+ }
+
+ cfg, prs, err := confchange.Restore(confchange.Changer{
+ Tracker: r.prs,
+ LastIndex: raftlog.lastIndex(),
+ }, cs)
+ if err != nil {
+ panic(err)
+ }
+ assertConfStatesEquivalent(r.logger, cs, r.switchToConfig(cfg, prs))
+
+ if !IsEmptyHardState(hs) {
+ r.loadState(hs)
+ }
+ if c.Applied > 0 {
+ raftlog.appliedTo(c.Applied)
+ }
+ r.becomeFollower(r.Term, None)
+
+ var nodesStrs []string
+ for _, n := range r.prs.VoterNodes() {
+ nodesStrs = append(nodesStrs, fmt.Sprintf("%x", n))
+ }
+
+ r.logger.Infof("newRaft %x [peers: [%s], term: %d, commit: %d, applied: %d, lastindex: %d, lastterm: %d]",
+ r.id, strings.Join(nodesStrs, ","), r.Term, r.raftLog.committed, r.raftLog.applied, r.raftLog.lastIndex(), r.raftLog.lastTerm())
+ return r
+}
+
+func (r *raft) hasLeader() bool { return r.lead != None }
+
+func (r *raft) softState() *SoftState { return &SoftState{Lead: r.lead, RaftState: r.state} }
+
+func (r *raft) hardState() pb.HardState {
+ return pb.HardState{
+ Term: r.Term,
+ Vote: r.Vote,
+ Commit: r.raftLog.committed,
+ }
+}
+
+// send persists state to stable storage and then sends to its mailbox.
+func (r *raft) send(m pb.Message) {
+ m.From = r.id
+ if m.Type == pb.MsgVote || m.Type == pb.MsgVoteResp || m.Type == pb.MsgPreVote || m.Type == pb.MsgPreVoteResp {
+ if m.Term == 0 {
+ // All {pre-,}campaign messages need to have the term set when
+ // sending.
+ // - MsgVote: m.Term is the term the node is campaigning for,
+ // non-zero as we increment the term when campaigning.
+ // - MsgVoteResp: m.Term is the new r.Term if the MsgVote was
+ // granted, non-zero for the same reason MsgVote is
+ // - MsgPreVote: m.Term is the term the node will campaign,
+ // non-zero as we use m.Term to indicate the next term we'll be
+ // campaigning for
+ // - MsgPreVoteResp: m.Term is the term received in the original
+ // MsgPreVote if the pre-vote was granted, non-zero for the
+ // same reasons MsgPreVote is
+ panic(fmt.Sprintf("term should be set when sending %s", m.Type))
+ }
+ } else {
+ if m.Term != 0 {
+ panic(fmt.Sprintf("term should not be set when sending %s (was %d)", m.Type, m.Term))
+ }
+ // do not attach term to MsgProp, MsgReadIndex
+ // proposals are a way to forward to the leader and
+ // should be treated as local message.
+ // MsgReadIndex is also forwarded to leader.
+ if m.Type != pb.MsgProp && m.Type != pb.MsgReadIndex {
+ m.Term = r.Term
+ }
+ }
+ r.msgs = append(r.msgs, m)
+}
+
+// sendAppend sends an append RPC with new entries (if any) and the
+// current commit index to the given peer.
+func (r *raft) sendAppend(to uint64) {
+ r.maybeSendAppend(to, true)
+}
+
+// maybeSendAppend sends an append RPC with new entries to the given peer,
+// if necessary. Returns true if a message was sent. The sendIfEmpty
+// argument controls whether messages with no entries will be sent
+// ("empty" messages are useful to convey updated Commit indexes, but
+// are undesirable when we're sending multiple messages in a batch).
+func (r *raft) maybeSendAppend(to uint64, sendIfEmpty bool) bool {
+ pr := r.prs.Progress[to]
+ if pr.IsPaused() {
+ return false
+ }
+ m := pb.Message{}
+ m.To = to
+
+ term, errt := r.raftLog.term(pr.Next - 1)
+ ents, erre := r.raftLog.entries(pr.Next, r.maxMsgSize)
+ if len(ents) == 0 && !sendIfEmpty {
+ return false
+ }
+
+ if errt != nil || erre != nil { // send snapshot if we failed to get term or entries
+ if !pr.RecentActive {
+ r.logger.Debugf("ignore sending snapshot to %x since it is not recently active", to)
+ return false
+ }
+
+ m.Type = pb.MsgSnap
+ snapshot, err := r.raftLog.snapshot()
+ if err != nil {
+ if err == ErrSnapshotTemporarilyUnavailable {
+ r.logger.Debugf("%x failed to send snapshot to %x because snapshot is temporarily unavailable", r.id, to)
+ return false
+ }
+ panic(err) // TODO(bdarnell)
+ }
+ if IsEmptySnap(snapshot) {
+ panic("need non-empty snapshot")
+ }
+ m.Snapshot = snapshot
+ sindex, sterm := snapshot.Metadata.Index, snapshot.Metadata.Term
+ r.logger.Debugf("%x [firstindex: %d, commit: %d] sent snapshot[index: %d, term: %d] to %x [%s]",
+ r.id, r.raftLog.firstIndex(), r.raftLog.committed, sindex, sterm, to, pr)
+ pr.BecomeSnapshot(sindex)
+ r.logger.Debugf("%x paused sending replication messages to %x [%s]", r.id, to, pr)
+ } else {
+ m.Type = pb.MsgApp
+ m.Index = pr.Next - 1
+ m.LogTerm = term
+ m.Entries = ents
+ m.Commit = r.raftLog.committed
+ if n := len(m.Entries); n != 0 {
+ switch pr.State {
+ // optimistically increase the next when in StateReplicate
+ case tracker.StateReplicate:
+ last := m.Entries[n-1].Index
+ pr.OptimisticUpdate(last)
+ pr.Inflights.Add(last)
+ case tracker.StateProbe:
+ pr.ProbeSent = true
+ default:
+ r.logger.Panicf("%x is sending append in unhandled state %s", r.id, pr.State)
+ }
+ }
+ }
+ r.send(m)
+ return true
+}
+
+// sendHeartbeat sends a heartbeat RPC to the given peer.
+func (r *raft) sendHeartbeat(to uint64, ctx []byte) {
+ // Attach the commit as min(to.matched, r.committed).
+ // When the leader sends out heartbeat message,
+ // the receiver(follower) might not be matched with the leader
+ // or it might not have all the committed entries.
+ // The leader MUST NOT forward the follower's commit to
+ // an unmatched index.
+ commit := min(r.prs.Progress[to].Match, r.raftLog.committed)
+ m := pb.Message{
+ To: to,
+ Type: pb.MsgHeartbeat,
+ Commit: commit,
+ Context: ctx,
+ }
+
+ r.send(m)
+}
+
+// bcastAppend sends RPC, with entries to all peers that are not up-to-date
+// according to the progress recorded in r.prs.
+func (r *raft) bcastAppend() {
+ r.prs.Visit(func(id uint64, _ *tracker.Progress) {
+ if id == r.id {
+ return
+ }
+ r.sendAppend(id)
+ })
+}
+
+// bcastHeartbeat sends RPC, without entries to all the peers.
+func (r *raft) bcastHeartbeat() {
+ lastCtx := r.readOnly.lastPendingRequestCtx()
+ if len(lastCtx) == 0 {
+ r.bcastHeartbeatWithCtx(nil)
+ } else {
+ r.bcastHeartbeatWithCtx([]byte(lastCtx))
+ }
+}
+
+func (r *raft) bcastHeartbeatWithCtx(ctx []byte) {
+ r.prs.Visit(func(id uint64, _ *tracker.Progress) {
+ if id == r.id {
+ return
+ }
+ r.sendHeartbeat(id, ctx)
+ })
+}
+
+func (r *raft) advance(rd Ready) {
+ // If entries were applied (or a snapshot), update our cursor for
+ // the next Ready. Note that if the current HardState contains a
+ // new Commit index, this does not mean that we're also applying
+ // all of the new entries due to commit pagination by size.
+ if index := rd.appliedCursor(); index > 0 {
+ r.raftLog.appliedTo(index)
+ if r.prs.Config.AutoLeave && index >= r.pendingConfIndex && r.state == StateLeader {
+ // If the current (and most recent, at least for this leader's term)
+ // configuration should be auto-left, initiate that now.
+ ccdata, err := (&pb.ConfChangeV2{}).Marshal()
+ if err != nil {
+ panic(err)
+ }
+ ent := pb.Entry{
+ Type: pb.EntryConfChangeV2,
+ Data: ccdata,
+ }
+ if !r.appendEntry(ent) {
+ // If we could not append the entry, bump the pending conf index
+ // so that we'll try again later.
+ //
+ // TODO(tbg): test this case.
+ r.pendingConfIndex = r.raftLog.lastIndex()
+ } else {
+ r.logger.Infof("initiating automatic transition out of joint configuration %s", r.prs.Config)
+ }
+ }
+ }
+ r.reduceUncommittedSize(rd.CommittedEntries)
+
+ if len(rd.Entries) > 0 {
+ e := rd.Entries[len(rd.Entries)-1]
+ r.raftLog.stableTo(e.Index, e.Term)
+ }
+ if !IsEmptySnap(rd.Snapshot) {
+ r.raftLog.stableSnapTo(rd.Snapshot.Metadata.Index)
+ }
+}
+
+// maybeCommit attempts to advance the commit index. Returns true if
+// the commit index changed (in which case the caller should call
+// r.bcastAppend).
+func (r *raft) maybeCommit() bool {
+ mci := r.prs.Committed()
+ return r.raftLog.maybeCommit(mci, r.Term)
+}
+
+func (r *raft) reset(term uint64) {
+ if r.Term != term {
+ r.Term = term
+ r.Vote = None
+ }
+ r.lead = None
+
+ r.electionElapsed = 0
+ r.heartbeatElapsed = 0
+ r.resetRandomizedElectionTimeout()
+
+ r.abortLeaderTransfer()
+
+ r.prs.ResetVotes()
+ r.prs.Visit(func(id uint64, pr *tracker.Progress) {
+ *pr = tracker.Progress{
+ Match: 0,
+ Next: r.raftLog.lastIndex() + 1,
+ Inflights: tracker.NewInflights(r.prs.MaxInflight),
+ IsLearner: pr.IsLearner,
+ }
+ if id == r.id {
+ pr.Match = r.raftLog.lastIndex()
+ }
+ })
+
+ r.pendingConfIndex = 0
+ r.uncommittedSize = 0
+ r.readOnly = newReadOnly(r.readOnly.option)
+}
+
+func (r *raft) appendEntry(es ...pb.Entry) (accepted bool) {
+ li := r.raftLog.lastIndex()
+ for i := range es {
+ es[i].Term = r.Term
+ es[i].Index = li + 1 + uint64(i)
+ }
+ // Track the size of this uncommitted proposal.
+ if !r.increaseUncommittedSize(es) {
+ r.logger.Debugf(
+ "%x appending new entries to log would exceed uncommitted entry size limit; dropping proposal",
+ r.id,
+ )
+ // Drop the proposal.
+ return false
+ }
+ // use latest "last" index after truncate/append
+ li = r.raftLog.append(es...)
+ r.prs.Progress[r.id].MaybeUpdate(li)
+ // Regardless of maybeCommit's return, our caller will call bcastAppend.
+ r.maybeCommit()
+ return true
+}
+
+// tickElection is run by followers and candidates after r.electionTimeout.
+func (r *raft) tickElection() {
+ r.electionElapsed++
+
+ if r.promotable() && r.pastElectionTimeout() {
+ r.electionElapsed = 0
+ r.Step(pb.Message{From: r.id, Type: pb.MsgHup})
+ }
+}
+
+// tickHeartbeat is run by leaders to send a MsgBeat after r.heartbeatTimeout.
+func (r *raft) tickHeartbeat() {
+ r.heartbeatElapsed++
+ r.electionElapsed++
+
+ if r.electionElapsed >= r.electionTimeout {
+ r.electionElapsed = 0
+ if r.checkQuorum {
+ r.Step(pb.Message{From: r.id, Type: pb.MsgCheckQuorum})
+ }
+ // If current leader cannot transfer leadership in electionTimeout, it becomes leader again.
+ if r.state == StateLeader && r.leadTransferee != None {
+ r.abortLeaderTransfer()
+ }
+ }
+
+ if r.state != StateLeader {
+ return
+ }
+
+ if r.heartbeatElapsed >= r.heartbeatTimeout {
+ r.heartbeatElapsed = 0
+ r.Step(pb.Message{From: r.id, Type: pb.MsgBeat})
+ }
+}
+
+func (r *raft) becomeFollower(term uint64, lead uint64) {
+ r.step = stepFollower
+ r.reset(term)
+ r.tick = r.tickElection
+ r.lead = lead
+ r.state = StateFollower
+ r.logger.Infof("%x became follower at term %d", r.id, r.Term)
+}
+
+func (r *raft) becomeCandidate() {
+ // TODO(xiangli) remove the panic when the raft implementation is stable
+ if r.state == StateLeader {
+ panic("invalid transition [leader -> candidate]")
+ }
+ r.step = stepCandidate
+ r.reset(r.Term + 1)
+ r.tick = r.tickElection
+ r.Vote = r.id
+ r.state = StateCandidate
+ r.logger.Infof("%x became candidate at term %d", r.id, r.Term)
+}
+
+func (r *raft) becomePreCandidate() {
+ // TODO(xiangli) remove the panic when the raft implementation is stable
+ if r.state == StateLeader {
+ panic("invalid transition [leader -> pre-candidate]")
+ }
+ // Becoming a pre-candidate changes our step functions and state,
+ // but doesn't change anything else. In particular it does not increase
+ // r.Term or change r.Vote.
+ r.step = stepCandidate
+ r.prs.ResetVotes()
+ r.tick = r.tickElection
+ r.lead = None
+ r.state = StatePreCandidate
+ r.logger.Infof("%x became pre-candidate at term %d", r.id, r.Term)
+}
+
+func (r *raft) becomeLeader() {
+ // TODO(xiangli) remove the panic when the raft implementation is stable
+ if r.state == StateFollower {
+ panic("invalid transition [follower -> leader]")
+ }
+ r.step = stepLeader
+ r.reset(r.Term)
+ r.tick = r.tickHeartbeat
+ r.lead = r.id
+ r.state = StateLeader
+ // Followers enter replicate mode when they've been successfully probed
+ // (perhaps after having received a snapshot as a result). The leader is
+ // trivially in this state. Note that r.reset() has initialized this
+ // progress with the last index already.
+ r.prs.Progress[r.id].BecomeReplicate()
+
+ // Conservatively set the pendingConfIndex to the last index in the
+ // log. There may or may not be a pending config change, but it's
+ // safe to delay any future proposals until we commit all our
+ // pending log entries, and scanning the entire tail of the log
+ // could be expensive.
+ r.pendingConfIndex = r.raftLog.lastIndex()
+
+ emptyEnt := pb.Entry{Data: nil}
+ if !r.appendEntry(emptyEnt) {
+ // This won't happen because we just called reset() above.
+ r.logger.Panic("empty entry was dropped")
+ }
+ // As a special case, don't count the initial empty entry towards the
+ // uncommitted log quota. This is because we want to preserve the
+ // behavior of allowing one entry larger than quota if the current
+ // usage is zero.
+ r.reduceUncommittedSize([]pb.Entry{emptyEnt})
+ r.logger.Infof("%x became leader at term %d", r.id, r.Term)
+}
+
+// campaign transitions the raft instance to candidate state. This must only be
+// called after verifying that this is a legitimate transition.
+func (r *raft) campaign(t CampaignType) {
+ if !r.promotable() {
+ // This path should not be hit (callers are supposed to check), but
+ // better safe than sorry.
+ r.logger.Warningf("%x is unpromotable; campaign() should have been called", r.id)
+ }
+ var term uint64
+ var voteMsg pb.MessageType
+ if t == campaignPreElection {
+ r.becomePreCandidate()
+ voteMsg = pb.MsgPreVote
+ // PreVote RPCs are sent for the next term before we've incremented r.Term.
+ term = r.Term + 1
+ } else {
+ r.becomeCandidate()
+ voteMsg = pb.MsgVote
+ term = r.Term
+ }
+ if _, _, res := r.poll(r.id, voteRespMsgType(voteMsg), true); res == quorum.VoteWon {
+ // We won the election after voting for ourselves (which must mean that
+ // this is a single-node cluster). Advance to the next state.
+ if t == campaignPreElection {
+ r.campaign(campaignElection)
+ } else {
+ r.becomeLeader()
+ }
+ return
+ }
+ var ids []uint64
+ {
+ idMap := r.prs.Voters.IDs()
+ ids = make([]uint64, 0, len(idMap))
+ for id := range idMap {
+ ids = append(ids, id)
+ }
+ sort.Slice(ids, func(i, j int) bool { return ids[i] < ids[j] })
+ }
+ for _, id := range ids {
+ if id == r.id {
+ continue
+ }
+ r.logger.Infof("%x [logterm: %d, index: %d] sent %s request to %x at term %d",
+ r.id, r.raftLog.lastTerm(), r.raftLog.lastIndex(), voteMsg, id, r.Term)
+
+ var ctx []byte
+ if t == campaignTransfer {
+ ctx = []byte(t)
+ }
+ r.send(pb.Message{Term: term, To: id, Type: voteMsg, Index: r.raftLog.lastIndex(), LogTerm: r.raftLog.lastTerm(), Context: ctx})
+ }
+}
+
+func (r *raft) poll(id uint64, t pb.MessageType, v bool) (granted int, rejected int, result quorum.VoteResult) {
+ if v {
+ r.logger.Infof("%x received %s from %x at term %d", r.id, t, id, r.Term)
+ } else {
+ r.logger.Infof("%x received %s rejection from %x at term %d", r.id, t, id, r.Term)
+ }
+ r.prs.RecordVote(id, v)
+ return r.prs.TallyVotes()
+}
+
+func (r *raft) Step(m pb.Message) error {
+ // Handle the message term, which may result in our stepping down to a follower.
+ switch {
+ case m.Term == 0:
+ // local message
+ case m.Term > r.Term:
+ if m.Type == pb.MsgVote || m.Type == pb.MsgPreVote {
+ force := bytes.Equal(m.Context, []byte(campaignTransfer))
+ inLease := r.checkQuorum && r.lead != None && r.electionElapsed < r.electionTimeout
+ if !force && inLease {
+ // If a server receives a RequestVote request within the minimum election timeout
+ // of hearing from a current leader, it does not update its term or grant its vote
+ r.logger.Infof("%x [logterm: %d, index: %d, vote: %x] ignored %s from %x [logterm: %d, index: %d] at term %d: lease is not expired (remaining ticks: %d)",
+ r.id, r.raftLog.lastTerm(), r.raftLog.lastIndex(), r.Vote, m.Type, m.From, m.LogTerm, m.Index, r.Term, r.electionTimeout-r.electionElapsed)
+ return nil
+ }
+ }
+ switch {
+ case m.Type == pb.MsgPreVote:
+ // Never change our term in response to a PreVote
+ case m.Type == pb.MsgPreVoteResp && !m.Reject:
+ // We send pre-vote requests with a term in our future. If the
+ // pre-vote is granted, we will increment our term when we get a
+ // quorum. If it is not, the term comes from the node that
+ // rejected our vote so we should become a follower at the new
+ // term.
+ default:
+ r.logger.Infof("%x [term: %d] received a %s message with higher term from %x [term: %d]",
+ r.id, r.Term, m.Type, m.From, m.Term)
+ if m.Type == pb.MsgApp || m.Type == pb.MsgHeartbeat || m.Type == pb.MsgSnap {
+ r.becomeFollower(m.Term, m.From)
+ } else {
+ r.becomeFollower(m.Term, None)
+ }
+ }
+
+ case m.Term < r.Term:
+ if (r.checkQuorum || r.preVote) && (m.Type == pb.MsgHeartbeat || m.Type == pb.MsgApp) {
+ // We have received messages from a leader at a lower term. It is possible
+ // that these messages were simply delayed in the network, but this could
+ // also mean that this node has advanced its term number during a network
+ // partition, and it is now unable to either win an election or to rejoin
+ // the majority on the old term. If checkQuorum is false, this will be
+ // handled by incrementing term numbers in response to MsgVote with a
+ // higher term, but if checkQuorum is true we may not advance the term on
+ // MsgVote and must generate other messages to advance the term. The net
+ // result of these two features is to minimize the disruption caused by
+ // nodes that have been removed from the cluster's configuration: a
+ // removed node will send MsgVotes (or MsgPreVotes) which will be ignored,
+ // but it will not receive MsgApp or MsgHeartbeat, so it will not create
+ // disruptive term increases, by notifying leader of this node's activeness.
+ // The above comments also true for Pre-Vote
+ //
+ // When follower gets isolated, it soon starts an election ending
+ // up with a higher term than leader, although it won't receive enough
+ // votes to win the election. When it regains connectivity, this response
+ // with "pb.MsgAppResp" of higher term would force leader to step down.
+ // However, this disruption is inevitable to free this stuck node with
+ // fresh election. This can be prevented with Pre-Vote phase.
+ r.send(pb.Message{To: m.From, Type: pb.MsgAppResp})
+ } else if m.Type == pb.MsgPreVote {
+ // Before Pre-Vote enable, there may have candidate with higher term,
+ // but less log. After update to Pre-Vote, the cluster may deadlock if
+ // we drop messages with a lower term.
+ r.logger.Infof("%x [logterm: %d, index: %d, vote: %x] rejected %s from %x [logterm: %d, index: %d] at term %d",
+ r.id, r.raftLog.lastTerm(), r.raftLog.lastIndex(), r.Vote, m.Type, m.From, m.LogTerm, m.Index, r.Term)
+ r.send(pb.Message{To: m.From, Term: r.Term, Type: pb.MsgPreVoteResp, Reject: true})
+ } else {
+ // ignore other cases
+ r.logger.Infof("%x [term: %d] ignored a %s message with lower term from %x [term: %d]",
+ r.id, r.Term, m.Type, m.From, m.Term)
+ }
+ return nil
+ }
+
+ switch m.Type {
+ case pb.MsgHup:
+ if r.state != StateLeader {
+ if !r.promotable() {
+ r.logger.Warningf("%x is unpromotable and can not campaign; ignoring MsgHup", r.id)
+ return nil
+ }
+ ents, err := r.raftLog.slice(r.raftLog.applied+1, r.raftLog.committed+1, noLimit)
+ if err != nil {
+ r.logger.Panicf("unexpected error getting unapplied entries (%v)", err)
+ }
+ if n := numOfPendingConf(ents); n != 0 && r.raftLog.committed > r.raftLog.applied {
+ r.logger.Warningf("%x cannot campaign at term %d since there are still %d pending configuration changes to apply", r.id, r.Term, n)
+ return nil
+ }
+
+ r.logger.Infof("%x is starting a new election at term %d", r.id, r.Term)
+ if r.preVote {
+ r.campaign(campaignPreElection)
+ } else {
+ r.campaign(campaignElection)
+ }
+ } else {
+ r.logger.Debugf("%x ignoring MsgHup because already leader", r.id)
+ }
+
+ case pb.MsgVote, pb.MsgPreVote:
+ // We can vote if this is a repeat of a vote we've already cast...
+ canVote := r.Vote == m.From ||
+ // ...we haven't voted and we don't think there's a leader yet in this term...
+ (r.Vote == None && r.lead == None) ||
+ // ...or this is a PreVote for a future term...
+ (m.Type == pb.MsgPreVote && m.Term > r.Term)
+ // ...and we believe the candidate is up to date.
+ if canVote && r.raftLog.isUpToDate(m.Index, m.LogTerm) {
+ // Note: it turns out that that learners must be allowed to cast votes.
+ // This seems counter- intuitive but is necessary in the situation in which
+ // a learner has been promoted (i.e. is now a voter) but has not learned
+ // about this yet.
+ // For example, consider a group in which id=1 is a learner and id=2 and
+ // id=3 are voters. A configuration change promoting 1 can be committed on
+ // the quorum `{2,3}` without the config change being appended to the
+ // learner's log. If the leader (say 2) fails, there are de facto two
+ // voters remaining. Only 3 can win an election (due to its log containing
+ // all committed entries), but to do so it will need 1 to vote. But 1
+ // considers itself a learner and will continue to do so until 3 has
+ // stepped up as leader, replicates the conf change to 1, and 1 applies it.
+ // Ultimately, by receiving a request to vote, the learner realizes that
+ // the candidate believes it to be a voter, and that it should act
+ // accordingly. The candidate's config may be stale, too; but in that case
+ // it won't win the election, at least in the absence of the bug discussed
+ // in:
+ // https://github.com/etcd-io/etcd/issues/7625#issuecomment-488798263.
+ r.logger.Infof("%x [logterm: %d, index: %d, vote: %x] cast %s for %x [logterm: %d, index: %d] at term %d",
+ r.id, r.raftLog.lastTerm(), r.raftLog.lastIndex(), r.Vote, m.Type, m.From, m.LogTerm, m.Index, r.Term)
+ // When responding to Msg{Pre,}Vote messages we include the term
+ // from the message, not the local term. To see why, consider the
+ // case where a single node was previously partitioned away and
+ // it's local term is now out of date. If we include the local term
+ // (recall that for pre-votes we don't update the local term), the
+ // (pre-)campaigning node on the other end will proceed to ignore
+ // the message (it ignores all out of date messages).
+ // The term in the original message and current local term are the
+ // same in the case of regular votes, but different for pre-votes.
+ r.send(pb.Message{To: m.From, Term: m.Term, Type: voteRespMsgType(m.Type)})
+ if m.Type == pb.MsgVote {
+ // Only record real votes.
+ r.electionElapsed = 0
+ r.Vote = m.From
+ }
+ } else {
+ r.logger.Infof("%x [logterm: %d, index: %d, vote: %x] rejected %s from %x [logterm: %d, index: %d] at term %d",
+ r.id, r.raftLog.lastTerm(), r.raftLog.lastIndex(), r.Vote, m.Type, m.From, m.LogTerm, m.Index, r.Term)
+ r.send(pb.Message{To: m.From, Term: r.Term, Type: voteRespMsgType(m.Type), Reject: true})
+ }
+
+ default:
+ err := r.step(r, m)
+ if err != nil {
+ return err
+ }
+ }
+ return nil
+}
+
+type stepFunc func(r *raft, m pb.Message) error
+
+func stepLeader(r *raft, m pb.Message) error {
+ // These message types do not require any progress for m.From.
+ switch m.Type {
+ case pb.MsgBeat:
+ r.bcastHeartbeat()
+ return nil
+ case pb.MsgCheckQuorum:
+ // The leader should always see itself as active. As a precaution, handle
+ // the case in which the leader isn't in the configuration any more (for
+ // example if it just removed itself).
+ //
+ // TODO(tbg): I added a TODO in removeNode, it doesn't seem that the
+ // leader steps down when removing itself. I might be missing something.
+ if pr := r.prs.Progress[r.id]; pr != nil {
+ pr.RecentActive = true
+ }
+ if !r.prs.QuorumActive() {
+ r.logger.Warningf("%x stepped down to follower since quorum is not active", r.id)
+ r.becomeFollower(r.Term, None)
+ }
+ // Mark everyone (but ourselves) as inactive in preparation for the next
+ // CheckQuorum.
+ r.prs.Visit(func(id uint64, pr *tracker.Progress) {
+ if id != r.id {
+ pr.RecentActive = false
+ }
+ })
+ return nil
+ case pb.MsgProp:
+ if len(m.Entries) == 0 {
+ r.logger.Panicf("%x stepped empty MsgProp", r.id)
+ }
+ if r.prs.Progress[r.id] == nil {
+ // If we are not currently a member of the range (i.e. this node
+ // was removed from the configuration while serving as leader),
+ // drop any new proposals.
+ return ErrProposalDropped
+ }
+ if r.leadTransferee != None {
+ r.logger.Debugf("%x [term %d] transfer leadership to %x is in progress; dropping proposal", r.id, r.Term, r.leadTransferee)
+ return ErrProposalDropped
+ }
+
+ for i := range m.Entries {
+ e := &m.Entries[i]
+ var cc pb.ConfChangeI
+ if e.Type == pb.EntryConfChange {
+ var ccc pb.ConfChange
+ if err := ccc.Unmarshal(e.Data); err != nil {
+ panic(err)
+ }
+ cc = ccc
+ } else if e.Type == pb.EntryConfChangeV2 {
+ var ccc pb.ConfChangeV2
+ if err := ccc.Unmarshal(e.Data); err != nil {
+ panic(err)
+ }
+ cc = ccc
+ }
+ if cc != nil {
+ alreadyPending := r.pendingConfIndex > r.raftLog.applied
+ alreadyJoint := len(r.prs.Config.Voters[1]) > 0
+ wantsLeaveJoint := len(cc.AsV2().Changes) == 0
+
+ var refused string
+ if alreadyPending {
+ refused = fmt.Sprintf("possible unapplied conf change at index %d (applied to %d)", r.pendingConfIndex, r.raftLog.applied)
+ } else if alreadyJoint && !wantsLeaveJoint {
+ refused = "must transition out of joint config first"
+ } else if !alreadyJoint && wantsLeaveJoint {
+ refused = "not in joint state; refusing empty conf change"
+ }
+
+ if refused != "" {
+ r.logger.Infof("%x ignoring conf change %v at config %s: %s", r.id, cc, r.prs.Config, refused)
+ m.Entries[i] = pb.Entry{Type: pb.EntryNormal}
+ } else {
+ r.pendingConfIndex = r.raftLog.lastIndex() + uint64(i) + 1
+ }
+ }
+ }
+
+ if !r.appendEntry(m.Entries...) {
+ return ErrProposalDropped
+ }
+ r.bcastAppend()
+ return nil
+ case pb.MsgReadIndex:
+ // If more than the local vote is needed, go through a full broadcast,
+ // otherwise optimize.
+ if !r.prs.IsSingleton() {
+ if r.raftLog.zeroTermOnErrCompacted(r.raftLog.term(r.raftLog.committed)) != r.Term {
+ // Reject read only request when this leader has not committed any log entry at its term.
+ return nil
+ }
+
+ // thinking: use an interally defined context instead of the user given context.
+ // We can express this in terms of the term and index instead of a user-supplied value.
+ // This would allow multiple reads to piggyback on the same message.
+ switch r.readOnly.option {
+ case ReadOnlySafe:
+ r.readOnly.addRequest(r.raftLog.committed, m)
+ // The local node automatically acks the request.
+ r.readOnly.recvAck(r.id, m.Entries[0].Data)
+ r.bcastHeartbeatWithCtx(m.Entries[0].Data)
+ case ReadOnlyLeaseBased:
+ ri := r.raftLog.committed
+ if m.From == None || m.From == r.id { // from local member
+ r.readStates = append(r.readStates, ReadState{Index: ri, RequestCtx: m.Entries[0].Data})
+ } else {
+ r.send(pb.Message{To: m.From, Type: pb.MsgReadIndexResp, Index: ri, Entries: m.Entries})
+ }
+ }
+ } else { // only one voting member (the leader) in the cluster
+ if m.From == None || m.From == r.id { // from leader itself
+ r.readStates = append(r.readStates, ReadState{Index: r.raftLog.committed, RequestCtx: m.Entries[0].Data})
+ } else { // from learner member
+ r.send(pb.Message{To: m.From, Type: pb.MsgReadIndexResp, Index: r.raftLog.committed, Entries: m.Entries})
+ }
+ }
+
+ return nil
+ }
+
+ // All other message types require a progress for m.From (pr).
+ pr := r.prs.Progress[m.From]
+ if pr == nil {
+ r.logger.Debugf("%x no progress available for %x", r.id, m.From)
+ return nil
+ }
+ switch m.Type {
+ case pb.MsgAppResp:
+ pr.RecentActive = true
+
+ if m.Reject {
+ r.logger.Debugf("%x received MsgAppResp(MsgApp was rejected, lastindex: %d) from %x for index %d",
+ r.id, m.RejectHint, m.From, m.Index)
+ if pr.MaybeDecrTo(m.Index, m.RejectHint) {
+ r.logger.Debugf("%x decreased progress of %x to [%s]", r.id, m.From, pr)
+ if pr.State == tracker.StateReplicate {
+ pr.BecomeProbe()
+ }
+ r.sendAppend(m.From)
+ }
+ } else {
+ oldPaused := pr.IsPaused()
+ if pr.MaybeUpdate(m.Index) {
+ switch {
+ case pr.State == tracker.StateProbe:
+ pr.BecomeReplicate()
+ case pr.State == tracker.StateSnapshot && pr.Match >= pr.PendingSnapshot:
+ // TODO(tbg): we should also enter this branch if a snapshot is
+ // received that is below pr.PendingSnapshot but which makes it
+ // possible to use the log again.
+ r.logger.Debugf("%x recovered from needing snapshot, resumed sending replication messages to %x [%s]", r.id, m.From, pr)
+ // Transition back to replicating state via probing state
+ // (which takes the snapshot into account). If we didn't
+ // move to replicating state, that would only happen with
+ // the next round of appends (but there may not be a next
+ // round for a while, exposing an inconsistent RaftStatus).
+ pr.BecomeProbe()
+ pr.BecomeReplicate()
+ case pr.State == tracker.StateReplicate:
+ pr.Inflights.FreeLE(m.Index)
+ }
+
+ if r.maybeCommit() {
+ r.bcastAppend()
+ } else if oldPaused {
+ // If we were paused before, this node may be missing the
+ // latest commit index, so send it.
+ r.sendAppend(m.From)
+ }
+ // We've updated flow control information above, which may
+ // allow us to send multiple (size-limited) in-flight messages
+ // at once (such as when transitioning from probe to
+ // replicate, or when freeTo() covers multiple messages). If
+ // we have more entries to send, send as many messages as we
+ // can (without sending empty messages for the commit index)
+ for r.maybeSendAppend(m.From, false) {
+ }
+ // Transfer leadership is in progress.
+ if m.From == r.leadTransferee && pr.Match == r.raftLog.lastIndex() {
+ r.logger.Infof("%x sent MsgTimeoutNow to %x after received MsgAppResp", r.id, m.From)
+ r.sendTimeoutNow(m.From)
+ }
+ }
+ }
+ case pb.MsgHeartbeatResp:
+ pr.RecentActive = true
+ pr.ProbeSent = false
+
+ // free one slot for the full inflights window to allow progress.
+ if pr.State == tracker.StateReplicate && pr.Inflights.Full() {
+ pr.Inflights.FreeFirstOne()
+ }
+ if pr.Match < r.raftLog.lastIndex() {
+ r.sendAppend(m.From)
+ }
+
+ if r.readOnly.option != ReadOnlySafe || len(m.Context) == 0 {
+ return nil
+ }
+
+ if r.prs.Voters.VoteResult(r.readOnly.recvAck(m.From, m.Context)) != quorum.VoteWon {
+ return nil
+ }
+
+ rss := r.readOnly.advance(m)
+ for _, rs := range rss {
+ req := rs.req
+ if req.From == None || req.From == r.id { // from local member
+ r.readStates = append(r.readStates, ReadState{Index: rs.index, RequestCtx: req.Entries[0].Data})
+ } else {
+ r.send(pb.Message{To: req.From, Type: pb.MsgReadIndexResp, Index: rs.index, Entries: req.Entries})
+ }
+ }
+ case pb.MsgSnapStatus:
+ if pr.State != tracker.StateSnapshot {
+ return nil
+ }
+ // TODO(tbg): this code is very similar to the snapshot handling in
+ // MsgAppResp above. In fact, the code there is more correct than the
+ // code here and should likely be updated to match (or even better, the
+ // logic pulled into a newly created Progress state machine handler).
+ if !m.Reject {
+ pr.BecomeProbe()
+ r.logger.Debugf("%x snapshot succeeded, resumed sending replication messages to %x [%s]", r.id, m.From, pr)
+ } else {
+ // NB: the order here matters or we'll be probing erroneously from
+ // the snapshot index, but the snapshot never applied.
+ pr.PendingSnapshot = 0
+ pr.BecomeProbe()
+ r.logger.Debugf("%x snapshot failed, resumed sending replication messages to %x [%s]", r.id, m.From, pr)
+ }
+ // If snapshot finish, wait for the MsgAppResp from the remote node before sending
+ // out the next MsgApp.
+ // If snapshot failure, wait for a heartbeat interval before next try
+ pr.ProbeSent = true
+ case pb.MsgUnreachable:
+ // During optimistic replication, if the remote becomes unreachable,
+ // there is huge probability that a MsgApp is lost.
+ if pr.State == tracker.StateReplicate {
+ pr.BecomeProbe()
+ }
+ r.logger.Debugf("%x failed to send message to %x because it is unreachable [%s]", r.id, m.From, pr)
+ case pb.MsgTransferLeader:
+ if pr.IsLearner {
+ r.logger.Debugf("%x is learner. Ignored transferring leadership", r.id)
+ return nil
+ }
+ leadTransferee := m.From
+ lastLeadTransferee := r.leadTransferee
+ if lastLeadTransferee != None {
+ if lastLeadTransferee == leadTransferee {
+ r.logger.Infof("%x [term %d] transfer leadership to %x is in progress, ignores request to same node %x",
+ r.id, r.Term, leadTransferee, leadTransferee)
+ return nil
+ }
+ r.abortLeaderTransfer()
+ r.logger.Infof("%x [term %d] abort previous transferring leadership to %x", r.id, r.Term, lastLeadTransferee)
+ }
+ if leadTransferee == r.id {
+ r.logger.Debugf("%x is already leader. Ignored transferring leadership to self", r.id)
+ return nil
+ }
+ // Transfer leadership to third party.
+ r.logger.Infof("%x [term %d] starts to transfer leadership to %x", r.id, r.Term, leadTransferee)
+ // Transfer leadership should be finished in one electionTimeout, so reset r.electionElapsed.
+ r.electionElapsed = 0
+ r.leadTransferee = leadTransferee
+ if pr.Match == r.raftLog.lastIndex() {
+ r.sendTimeoutNow(leadTransferee)
+ r.logger.Infof("%x sends MsgTimeoutNow to %x immediately as %x already has up-to-date log", r.id, leadTransferee, leadTransferee)
+ } else {
+ r.sendAppend(leadTransferee)
+ }
+ }
+ return nil
+}
+
+// stepCandidate is shared by StateCandidate and StatePreCandidate; the difference is
+// whether they respond to MsgVoteResp or MsgPreVoteResp.
+func stepCandidate(r *raft, m pb.Message) error {
+ // Only handle vote responses corresponding to our candidacy (while in
+ // StateCandidate, we may get stale MsgPreVoteResp messages in this term from
+ // our pre-candidate state).
+ var myVoteRespType pb.MessageType
+ if r.state == StatePreCandidate {
+ myVoteRespType = pb.MsgPreVoteResp
+ } else {
+ myVoteRespType = pb.MsgVoteResp
+ }
+ switch m.Type {
+ case pb.MsgProp:
+ r.logger.Infof("%x no leader at term %d; dropping proposal", r.id, r.Term)
+ return ErrProposalDropped
+ case pb.MsgApp:
+ r.becomeFollower(m.Term, m.From) // always m.Term == r.Term
+ r.handleAppendEntries(m)
+ case pb.MsgHeartbeat:
+ r.becomeFollower(m.Term, m.From) // always m.Term == r.Term
+ r.handleHeartbeat(m)
+ case pb.MsgSnap:
+ r.becomeFollower(m.Term, m.From) // always m.Term == r.Term
+ r.handleSnapshot(m)
+ case myVoteRespType:
+ gr, rj, res := r.poll(m.From, m.Type, !m.Reject)
+ r.logger.Infof("%x has received %d %s votes and %d vote rejections", r.id, gr, m.Type, rj)
+ switch res {
+ case quorum.VoteWon:
+ if r.state == StatePreCandidate {
+ r.campaign(campaignElection)
+ } else {
+ r.becomeLeader()
+ r.bcastAppend()
+ }
+ case quorum.VoteLost:
+ // pb.MsgPreVoteResp contains future term of pre-candidate
+ // m.Term > r.Term; reuse r.Term
+ r.becomeFollower(r.Term, None)
+ }
+ case pb.MsgTimeoutNow:
+ r.logger.Debugf("%x [term %d state %v] ignored MsgTimeoutNow from %x", r.id, r.Term, r.state, m.From)
+ }
+ return nil
+}
+
+func stepFollower(r *raft, m pb.Message) error {
+ switch m.Type {
+ case pb.MsgProp:
+ if r.lead == None {
+ r.logger.Infof("%x no leader at term %d; dropping proposal", r.id, r.Term)
+ return ErrProposalDropped
+ } else if r.disableProposalForwarding {
+ r.logger.Infof("%x not forwarding to leader %x at term %d; dropping proposal", r.id, r.lead, r.Term)
+ return ErrProposalDropped
+ }
+ m.To = r.lead
+ r.send(m)
+ case pb.MsgApp:
+ r.electionElapsed = 0
+ r.lead = m.From
+ r.handleAppendEntries(m)
+ case pb.MsgHeartbeat:
+ r.electionElapsed = 0
+ r.lead = m.From
+ r.handleHeartbeat(m)
+ case pb.MsgSnap:
+ r.electionElapsed = 0
+ r.lead = m.From
+ r.handleSnapshot(m)
+ case pb.MsgTransferLeader:
+ if r.lead == None {
+ r.logger.Infof("%x no leader at term %d; dropping leader transfer msg", r.id, r.Term)
+ return nil
+ }
+ m.To = r.lead
+ r.send(m)
+ case pb.MsgTimeoutNow:
+ if r.promotable() {
+ r.logger.Infof("%x [term %d] received MsgTimeoutNow from %x and starts an election to get leadership.", r.id, r.Term, m.From)
+ // Leadership transfers never use pre-vote even if r.preVote is true; we
+ // know we are not recovering from a partition so there is no need for the
+ // extra round trip.
+ r.campaign(campaignTransfer)
+ } else {
+ r.logger.Infof("%x received MsgTimeoutNow from %x but is not promotable", r.id, m.From)
+ }
+ case pb.MsgReadIndex:
+ if r.lead == None {
+ r.logger.Infof("%x no leader at term %d; dropping index reading msg", r.id, r.Term)
+ return nil
+ }
+ m.To = r.lead
+ r.send(m)
+ case pb.MsgReadIndexResp:
+ if len(m.Entries) != 1 {
+ r.logger.Errorf("%x invalid format of MsgReadIndexResp from %x, entries count: %d", r.id, m.From, len(m.Entries))
+ return nil
+ }
+ r.readStates = append(r.readStates, ReadState{Index: m.Index, RequestCtx: m.Entries[0].Data})
+ }
+ return nil
+}
+
+func (r *raft) handleAppendEntries(m pb.Message) {
+ if m.Index < r.raftLog.committed {
+ r.send(pb.Message{To: m.From, Type: pb.MsgAppResp, Index: r.raftLog.committed})
+ return
+ }
+
+ if mlastIndex, ok := r.raftLog.maybeAppend(m.Index, m.LogTerm, m.Commit, m.Entries...); ok {
+ r.send(pb.Message{To: m.From, Type: pb.MsgAppResp, Index: mlastIndex})
+ } else {
+ r.logger.Debugf("%x [logterm: %d, index: %d] rejected MsgApp [logterm: %d, index: %d] from %x",
+ r.id, r.raftLog.zeroTermOnErrCompacted(r.raftLog.term(m.Index)), m.Index, m.LogTerm, m.Index, m.From)
+ r.send(pb.Message{To: m.From, Type: pb.MsgAppResp, Index: m.Index, Reject: true, RejectHint: r.raftLog.lastIndex()})
+ }
+}
+
+func (r *raft) handleHeartbeat(m pb.Message) {
+ r.raftLog.commitTo(m.Commit)
+ r.send(pb.Message{To: m.From, Type: pb.MsgHeartbeatResp, Context: m.Context})
+}
+
+func (r *raft) handleSnapshot(m pb.Message) {
+ sindex, sterm := m.Snapshot.Metadata.Index, m.Snapshot.Metadata.Term
+ if r.restore(m.Snapshot) {
+ r.logger.Infof("%x [commit: %d] restored snapshot [index: %d, term: %d]",
+ r.id, r.raftLog.committed, sindex, sterm)
+ r.send(pb.Message{To: m.From, Type: pb.MsgAppResp, Index: r.raftLog.lastIndex()})
+ } else {
+ r.logger.Infof("%x [commit: %d] ignored snapshot [index: %d, term: %d]",
+ r.id, r.raftLog.committed, sindex, sterm)
+ r.send(pb.Message{To: m.From, Type: pb.MsgAppResp, Index: r.raftLog.committed})
+ }
+}
+
+// restore recovers the state machine from a snapshot. It restores the log and the
+// configuration of state machine. If this method returns false, the snapshot was
+// ignored, either because it was obsolete or because of an error.
+func (r *raft) restore(s pb.Snapshot) bool {
+ if s.Metadata.Index <= r.raftLog.committed {
+ return false
+ }
+ if r.state != StateFollower {
+ // This is defense-in-depth: if the leader somehow ended up applying a
+ // snapshot, it could move into a new term without moving into a
+ // follower state. This should never fire, but if it did, we'd have
+ // prevented damage by returning early, so log only a loud warning.
+ //
+ // At the time of writing, the instance is guaranteed to be in follower
+ // state when this method is called.
+ r.logger.Warningf("%x attempted to restore snapshot as leader; should never happen", r.id)
+ r.becomeFollower(r.Term+1, None)
+ return false
+ }
+
+ // More defense-in-depth: throw away snapshot if recipient is not in the
+ // config. This shouldn't ever happen (at the time of writing) but lots of
+ // code here and there assumes that r.id is in the progress tracker.
+ found := false
+ cs := s.Metadata.ConfState
+ for _, set := range [][]uint64{
+ cs.Voters,
+ cs.Learners,
+ } {
+ for _, id := range set {
+ if id == r.id {
+ found = true
+ break
+ }
+ }
+ }
+ if !found {
+ r.logger.Warningf(
+ "%x attempted to restore snapshot but it is not in the ConfState %v; should never happen",
+ r.id, cs,
+ )
+ return false
+ }
+
+ // Now go ahead and actually restore.
+
+ if r.raftLog.matchTerm(s.Metadata.Index, s.Metadata.Term) {
+ r.logger.Infof("%x [commit: %d, lastindex: %d, lastterm: %d] fast-forwarded commit to snapshot [index: %d, term: %d]",
+ r.id, r.raftLog.committed, r.raftLog.lastIndex(), r.raftLog.lastTerm(), s.Metadata.Index, s.Metadata.Term)
+ r.raftLog.commitTo(s.Metadata.Index)
+ return false
+ }
+
+ r.raftLog.restore(s)
+
+ // Reset the configuration and add the (potentially updated) peers in anew.
+ r.prs = tracker.MakeProgressTracker(r.prs.MaxInflight)
+ cfg, prs, err := confchange.Restore(confchange.Changer{
+ Tracker: r.prs,
+ LastIndex: r.raftLog.lastIndex(),
+ }, cs)
+
+ if err != nil {
+ // This should never happen. Either there's a bug in our config change
+ // handling or the client corrupted the conf change.
+ panic(fmt.Sprintf("unable to restore config %+v: %s", cs, err))
+ }
+
+ assertConfStatesEquivalent(r.logger, cs, r.switchToConfig(cfg, prs))
+
+ pr := r.prs.Progress[r.id]
+ pr.MaybeUpdate(pr.Next - 1) // TODO(tbg): this is untested and likely unneeded
+
+ r.logger.Infof("%x [commit: %d, lastindex: %d, lastterm: %d] restored snapshot [index: %d, term: %d]",
+ r.id, r.raftLog.committed, r.raftLog.lastIndex(), r.raftLog.lastTerm(), s.Metadata.Index, s.Metadata.Term)
+ return true
+}
+
+// promotable indicates whether state machine can be promoted to leader,
+// which is true when its own id is in progress list.
+func (r *raft) promotable() bool {
+ pr := r.prs.Progress[r.id]
+ return pr != nil && !pr.IsLearner
+}
+
+func (r *raft) applyConfChange(cc pb.ConfChangeV2) pb.ConfState {
+ cfg, prs, err := func() (tracker.Config, tracker.ProgressMap, error) {
+ changer := confchange.Changer{
+ Tracker: r.prs,
+ LastIndex: r.raftLog.lastIndex(),
+ }
+ if cc.LeaveJoint() {
+ return changer.LeaveJoint()
+ } else if autoLeave, ok := cc.EnterJoint(); ok {
+ return changer.EnterJoint(autoLeave, cc.Changes...)
+ }
+ return changer.Simple(cc.Changes...)
+ }()
+
+ if err != nil {
+ // TODO(tbg): return the error to the caller.
+ panic(err)
+ }
+
+ return r.switchToConfig(cfg, prs)
+}
+
+// switchToConfig reconfigures this node to use the provided configuration. It
+// updates the in-memory state and, when necessary, carries out additional
+// actions such as reacting to the removal of nodes or changed quorum
+// requirements.
+//
+// The inputs usually result from restoring a ConfState or applying a ConfChange.
+func (r *raft) switchToConfig(cfg tracker.Config, prs tracker.ProgressMap) pb.ConfState {
+ r.prs.Config = cfg
+ r.prs.Progress = prs
+
+ r.logger.Infof("%x switched to configuration %s", r.id, r.prs.Config)
+ cs := r.prs.ConfState()
+ pr, ok := r.prs.Progress[r.id]
+
+ // Update whether the node itself is a learner, resetting to false when the
+ // node is removed.
+ r.isLearner = ok && pr.IsLearner
+
+ if (!ok || r.isLearner) && r.state == StateLeader {
+ // This node is leader and was removed or demoted. We prevent demotions
+ // at the time writing but hypothetically we handle them the same way as
+ // removing the leader: stepping down into the next Term.
+ //
+ // TODO(tbg): step down (for sanity) and ask follower with largest Match
+ // to TimeoutNow (to avoid interruption). This might still drop some
+ // proposals but it's better than nothing.
+ //
+ // TODO(tbg): test this branch. It is untested at the time of writing.
+ return cs
+ }
+
+ // The remaining steps only make sense if this node is the leader and there
+ // are other nodes.
+ if r.state != StateLeader || len(cs.Voters) == 0 {
+ return cs
+ }
+
+ if r.maybeCommit() {
+ // If the configuration change means that more entries are committed now,
+ // broadcast/append to everyone in the updated config.
+ r.bcastAppend()
+ } else {
+ // Otherwise, still probe the newly added replicas; there's no reason to
+ // let them wait out a heartbeat interval (or the next incoming
+ // proposal).
+ r.prs.Visit(func(id uint64, pr *tracker.Progress) {
+ r.maybeSendAppend(id, false /* sendIfEmpty */)
+ })
+ }
+ // If the the leadTransferee was removed, abort the leadership transfer.
+ if _, tOK := r.prs.Progress[r.leadTransferee]; !tOK && r.leadTransferee != 0 {
+ r.abortLeaderTransfer()
+ }
+
+ return cs
+}
+
+func (r *raft) loadState(state pb.HardState) {
+ if state.Commit < r.raftLog.committed || state.Commit > r.raftLog.lastIndex() {
+ r.logger.Panicf("%x state.commit %d is out of range [%d, %d]", r.id, state.Commit, r.raftLog.committed, r.raftLog.lastIndex())
+ }
+ r.raftLog.committed = state.Commit
+ r.Term = state.Term
+ r.Vote = state.Vote
+}
+
+// pastElectionTimeout returns true iff r.electionElapsed is greater
+// than or equal to the randomized election timeout in
+// [electiontimeout, 2 * electiontimeout - 1].
+func (r *raft) pastElectionTimeout() bool {
+ return r.electionElapsed >= r.randomizedElectionTimeout
+}
+
+func (r *raft) resetRandomizedElectionTimeout() {
+ r.randomizedElectionTimeout = r.electionTimeout + globalRand.Intn(r.electionTimeout)
+}
+
+func (r *raft) sendTimeoutNow(to uint64) {
+ r.send(pb.Message{To: to, Type: pb.MsgTimeoutNow})
+}
+
+func (r *raft) abortLeaderTransfer() {
+ r.leadTransferee = None
+}
+
+// increaseUncommittedSize computes the size of the proposed entries and
+// determines whether they would push leader over its maxUncommittedSize limit.
+// If the new entries would exceed the limit, the method returns false. If not,
+// the increase in uncommitted entry size is recorded and the method returns
+// true.
+func (r *raft) increaseUncommittedSize(ents []pb.Entry) bool {
+ var s uint64
+ for _, e := range ents {
+ s += uint64(PayloadSize(e))
+ }
+
+ if r.uncommittedSize > 0 && r.uncommittedSize+s > r.maxUncommittedSize {
+ // If the uncommitted tail of the Raft log is empty, allow any size
+ // proposal. Otherwise, limit the size of the uncommitted tail of the
+ // log and drop any proposal that would push the size over the limit.
+ return false
+ }
+ r.uncommittedSize += s
+ return true
+}
+
+// reduceUncommittedSize accounts for the newly committed entries by decreasing
+// the uncommitted entry size limit.
+func (r *raft) reduceUncommittedSize(ents []pb.Entry) {
+ if r.uncommittedSize == 0 {
+ // Fast-path for followers, who do not track or enforce the limit.
+ return
+ }
+
+ var s uint64
+ for _, e := range ents {
+ s += uint64(PayloadSize(e))
+ }
+ if s > r.uncommittedSize {
+ // uncommittedSize may underestimate the size of the uncommitted Raft
+ // log tail but will never overestimate it. Saturate at 0 instead of
+ // allowing overflow.
+ r.uncommittedSize = 0
+ } else {
+ r.uncommittedSize -= s
+ }
+}
+
+func numOfPendingConf(ents []pb.Entry) int {
+ n := 0
+ for i := range ents {
+ if ents[i].Type == pb.EntryConfChange {
+ n++
+ }
+ }
+ return n
+}