Update etcd client to 3.3.9

vendor/github.com/coreos/etcd/raft/BUILD

@@ -19,10 +19,7 @@ go_library(
     importmap = "k8s.io/kubernetes/vendor/github.com/coreos/etcd/raft",
     importpath = "github.com/coreos/etcd/raft",
     visibility = ["//visibility:public"],
-    deps = [
-        "//vendor/github.com/coreos/etcd/raft/raftpb:go_default_library",
-        "//vendor/golang.org/x/net/context:go_default_library",
-    ],
+    deps = ["//vendor/github.com/coreos/etcd/raft/raftpb:go_default_library"],
 )
 
 filegroup(

vendor/github.com/coreos/etcd/raft/README.md

@@ -25,12 +25,12 @@ This raft implementation is a full feature implementation of Raft protocol. Feat
 - Membership changes
 - Leadership transfer extension
 - Efficient linearizable read-only queries served by both the leader and followers
- - leader checks with quorum and bypasses Raft log before processing read-only queries
- - followers asks leader to get a safe read index before processing read-only queries
+  - leader checks with quorum and bypasses Raft log before processing read-only queries
+  - followers asks leader to get a safe read index before processing read-only queries
 - More efficient lease-based linearizable read-only queries served by both the leader and followers
- - leader bypasses Raft log and processing read-only queries locally
- - followers asks leader to get a safe read index before processing read-only queries
- - this approach relies on the clock of the all the machines in raft group
+  - leader bypasses Raft log and processing read-only queries locally
+  - followers asks leader to get a safe read index before processing read-only queries
+  - this approach relies on the clock of the all the machines in raft group
 
 This raft implementation also includes a few optional enhancements:
 
@@ -112,7 +112,7 @@ After creating a Node, the user has a few responsibilities:
 
 First, read from the Node.Ready() channel and process the updates it contains. These steps may be performed in parallel, except as noted in step 2.
 
-1. Write HardState, Entries, and Snapshot to persistent storage if they are not empty. Note that when writing an Entry with Index i, any previously-persisted entries with Index >= i must be discarded.
+1. Write Entries, HardState and Snapshot to persistent storage in order, i.e. Entries first, then HardState and Snapshot if they are not empty. If persistent storage supports atomic writes then all of them can be written together. Note that when writing an Entry with Index i, any previously-persisted entries with Index >= i must be discarded.
 
 2. Send all Messages to the nodes named in the To field. It is important that no messages be sent until the latest HardState has been persisted to disk, and all Entries written by any previous Ready batch (Messages may be sent while entries from the same batch are being persisted). To reduce the I/O latency, an optimization can be applied to make leader write to disk in parallel with its followers (as explained at section 10.2.1 in Raft thesis). If any Message has type MsgSnap, call Node.ReportSnapshot() after it has been sent (these messages may be large). Note: Marshalling messages is not thread-safe; it is important to make sure that no new entries are persisted while marshalling. The easiest way to achieve this is to serialise the messages directly inside the main raft loop.
 

vendor/github.com/coreos/etcd/raft/node.go

@@ -15,10 +15,10 @@
 package raft
 
 import (
+	"context"
 	"errors"
 
 	pb "github.com/coreos/etcd/raft/raftpb"
-	"golang.org/x/net/context"
 )
 
 type SnapshotStatus int
@@ -319,7 +319,7 @@ func (n *node) run(r *raft) {
 			r.Step(m)
 		case m := <-n.recvc:
 			// filter out response message from unknown From.
-			if _, ok := r.prs[m.From]; ok || !IsResponseMsg(m.Type) {
+			if pr := r.getProgress(m.From); pr != nil || !IsResponseMsg(m.Type) {
 				r.Step(m) // raft never returns an error
 			}
 		case cc := <-n.confc:
@@ -334,6 +334,8 @@ func (n *node) run(r *raft) {
 			switch cc.Type {
 			case pb.ConfChangeAddNode:
 				r.addNode(cc.NodeID)
+			case pb.ConfChangeAddLearnerNode:
+				r.addLearner(cc.NodeID)
 			case pb.ConfChangeRemoveNode:
 				// block incoming proposal when local node is
 				// removed

vendor/github.com/coreos/etcd/raft/progress.go

@@ -48,6 +48,7 @@ type Progress struct {
 	// When in ProgressStateSnapshot, leader should have sent out snapshot
 	// before and stops sending any replication message.
 	State ProgressStateType
+
 	// Paused is used in ProgressStateProbe.
 	// When Paused is true, raft should pause sending replication message to this peer.
 	Paused bool
@@ -76,6 +77,9 @@ type Progress struct {
 	// be freed by calling inflights.freeTo with the index of the last
 	// received entry.
 	ins *inflights
+
+	// IsLearner is true if this progress is tracked for a learner.
+	IsLearner bool
 }
 
 func (pr *Progress) resetState(state ProgressStateType) {
@@ -243,7 +247,8 @@ func (in *inflights) freeTo(to uint64) {
 		return
 	}
 
-	i, idx := 0, in.start
+	idx := in.start
+	var i int
 	for i = 0; i < in.count; i++ {
 		if to < in.buffer[idx] { // found the first large inflight
 			break

vendor/github.com/coreos/etcd/raft/raft.go

@@ -116,6 +116,10 @@ type Config struct {
 	// used for testing right now.
 	peers []uint64
 
+	// learners contains the IDs of all leaner nodes (including self if the local node is a leaner) 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
@@ -171,11 +175,22 @@ type Config struct {
 	// 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 innaccurate hybrid
+	// logical clock from assigning the timestamp and then forwarding the data
+	// to the leader.
+	DisableProposalForwarding bool
 }
 
 func (c *Config) validate() error {
@@ -203,6 +218,10 @@ func (c *Config) validate() error {
 		c.Logger = raftLogger
 	}
 
+	if c.ReadOnlyOption == ReadOnlyLeaseBased && !c.CheckQuorum {
+		return errors.New("CheckQuorum must be enabled when ReadOnlyOption is ReadOnlyLeaseBased")
+	}
+
 	return nil
 }
 
@@ -220,9 +239,13 @@ type raft struct {
 	maxInflight int
 	maxMsgSize  uint64
 	prs         map[uint64]*Progress
+	learnerPrs  map[uint64]*Progress
 
 	state StateType
 
+	// isLearner is true if the local raft node is a learner.
+	isLearner bool
+
 	votes map[uint64]bool
 
 	msgs []pb.Message
@@ -256,6 +279,7 @@ type raft struct {
 	// [electiontimeout, 2 * electiontimeout - 1]. It gets reset
 	// when raft changes its state to follower or candidate.
 	randomizedElectionTimeout int
+	disableProposalForwarding bool
 
 	tick func()
 	step stepFunc
@@ -273,32 +297,47 @@ func newRaft(c *Config) *raft {
 		panic(err) // TODO(bdarnell)
 	}
 	peers := c.peers
-	if len(cs.Nodes) > 0 {
-		if len(peers) > 0 {
+	learners := c.learners
+	if len(cs.Nodes) > 0 || len(cs.Learners) > 0 {
+		if len(peers) > 0 || len(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) and ConfState.Nodes)")
+			panic("cannot specify both newRaft(peers, learners) and ConfState.(Nodes, Learners)")
 		}
 		peers = cs.Nodes
+		learners = cs.Learners
 	}
 	r := &raft{
-		id:               c.ID,
-		lead:             None,
-		raftLog:          raftlog,
-		maxMsgSize:       c.MaxSizePerMsg,
-		maxInflight:      c.MaxInflightMsgs,
-		prs:              make(map[uint64]*Progress),
-		electionTimeout:  c.ElectionTick,
-		heartbeatTimeout: c.HeartbeatTick,
-		logger:           c.Logger,
-		checkQuorum:      c.CheckQuorum,
-		preVote:          c.PreVote,
-		readOnly:         newReadOnly(c.ReadOnlyOption),
+		id:                        c.ID,
+		lead:                      None,
+		isLearner:                 false,
+		raftLog:                   raftlog,
+		maxMsgSize:                c.MaxSizePerMsg,
+		maxInflight:               c.MaxInflightMsgs,
+		prs:                       make(map[uint64]*Progress),
+		learnerPrs:                make(map[uint64]*Progress),
+		electionTimeout:           c.ElectionTick,
+		heartbeatTimeout:          c.HeartbeatTick,
+		logger:                    c.Logger,
+		checkQuorum:               c.CheckQuorum,
+		preVote:                   c.PreVote,
+		readOnly:                  newReadOnly(c.ReadOnlyOption),
+		disableProposalForwarding: c.DisableProposalForwarding,
 	}
 	for _, p := range peers {
 		r.prs[p] = &Progress{Next: 1, ins: newInflights(r.maxInflight)}
 	}
+	for _, p := range learners {
+		if _, ok := r.prs[p]; ok {
+			panic(fmt.Sprintf("node %x is in both learner and peer list", p))
+		}
+		r.learnerPrs[p] = &Progress{Next: 1, ins: newInflights(r.maxInflight), IsLearner: true}
+		if r.id == p {
+			r.isLearner = true
+		}
+	}
+
 	if !isHardStateEqual(hs, emptyState) {
 		r.loadState(hs)
 	}
@@ -332,10 +371,13 @@ func (r *raft) hardState() pb.HardState {
 func (r *raft) quorum() int { return len(r.prs)/2 + 1 }
 
 func (r *raft) nodes() []uint64 {
-	nodes := make([]uint64, 0, len(r.prs))
+	nodes := make([]uint64, 0, len(r.prs)+len(r.learnerPrs))
 	for id := range r.prs {
 		nodes = append(nodes, id)
 	}
+	for id := range r.learnerPrs {
+		nodes = append(nodes, id)
+	}
 	sort.Sort(uint64Slice(nodes))
 	return nodes
 }
@@ -343,10 +385,20 @@ func (r *raft) nodes() []uint64 {
 // 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.MsgPreVote {
+	if m.Type == pb.MsgVote || m.Type == pb.MsgVoteResp || m.Type == pb.MsgPreVote || m.Type == pb.MsgPreVoteResp {
 		if m.Term == 0 {
-			// PreVote RPCs are sent at a term other than our actual term, so the code
-			// that sends these messages is responsible for setting the term.
+			// 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 {
@@ -364,9 +416,17 @@ func (r *raft) send(m pb.Message) {
 	r.msgs = append(r.msgs, m)
 }
 
+func (r *raft) getProgress(id uint64) *Progress {
+	if pr, ok := r.prs[id]; ok {
+		return pr
+	}
+
+	return r.learnerPrs[id]
+}
+
 // sendAppend sends RPC, with entries to the given peer.
 func (r *raft) sendAppend(to uint64) {
-	pr := r.prs[to]
+	pr := r.getProgress(to)
 	if pr.IsPaused() {
 		return
 	}
@@ -431,7 +491,7 @@ func (r *raft) sendHeartbeat(to uint64, ctx []byte) {
 	// 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[to].Match, r.raftLog.committed)
+	commit := min(r.getProgress(to).Match, r.raftLog.committed)
 	m := pb.Message{
 		To:      to,
 		Type:    pb.MsgHeartbeat,
@@ -442,15 +502,26 @@ func (r *raft) sendHeartbeat(to uint64, ctx []byte) {
 	r.send(m)
 }
 
+func (r *raft) forEachProgress(f func(id uint64, pr *Progress)) {
+	for id, pr := range r.prs {
+		f(id, pr)
+	}
+
+	for id, pr := range r.learnerPrs {
+		f(id, pr)
+	}
+}
+
 // 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() {
-	for id := range r.prs {
+	r.forEachProgress(func(id uint64, _ *Progress) {
 		if id == r.id {
-			continue
+			return
 		}
+
 		r.sendAppend(id)
-	}
+	})
 }
 
 // bcastHeartbeat sends RPC, without entries to all the peers.
@@ -464,12 +535,12 @@ func (r *raft) bcastHeartbeat() {
 }
 
 func (r *raft) bcastHeartbeatWithCtx(ctx []byte) {
-	for id := range r.prs {
+	r.forEachProgress(func(id uint64, _ *Progress) {
 		if id == r.id {
-			continue
+			return
 		}
 		r.sendHeartbeat(id, ctx)
-	}
+	})
 }
 
 // maybeCommit attempts to advance the commit index. Returns true if
@@ -478,8 +549,8 @@ func (r *raft) bcastHeartbeatWithCtx(ctx []byte) {
 func (r *raft) maybeCommit() bool {
 	// TODO(bmizerany): optimize.. Currently naive
 	mis := make(uint64Slice, 0, len(r.prs))
-	for id := range r.prs {
-		mis = append(mis, r.prs[id].Match)
+	for _, p := range r.prs {
+		mis = append(mis, p.Match)
 	}
 	sort.Sort(sort.Reverse(mis))
 	mci := mis[r.quorum()-1]
@@ -500,12 +571,13 @@ func (r *raft) reset(term uint64) {
 	r.abortLeaderTransfer()
 
 	r.votes = make(map[uint64]bool)
-	for id := range r.prs {
-		r.prs[id] = &Progress{Next: r.raftLog.lastIndex() + 1, ins: newInflights(r.maxInflight)}
+	r.forEachProgress(func(id uint64, pr *Progress) {
+		*pr = Progress{Next: r.raftLog.lastIndex() + 1, ins: newInflights(r.maxInflight), IsLearner: pr.IsLearner}
 		if id == r.id {
-			r.prs[id].Match = r.raftLog.lastIndex()
+			pr.Match = r.raftLog.lastIndex()
 		}
-	}
+	})
+
 	r.pendingConf = false
 	r.readOnly = newReadOnly(r.readOnly.option)
 }
@@ -517,7 +589,7 @@ func (r *raft) appendEntry(es ...pb.Entry) {
 		es[i].Index = li + 1 + uint64(i)
 	}
 	r.raftLog.append(es...)
-	r.prs[r.id].maybeUpdate(r.raftLog.lastIndex())
+	r.getProgress(r.id).maybeUpdate(r.raftLog.lastIndex())
 	// Regardless of maybeCommit's return, our caller will call bcastAppend.
 	r.maybeCommit()
 }
@@ -589,6 +661,7 @@ func (r *raft) becomePreCandidate() {
 	// but doesn't change anything else. In particular it does not increase
 	// r.Term or change r.Vote.
 	r.step = stepCandidate
+	r.votes = make(map[uint64]bool)
 	r.tick = r.tickElection
 	r.state = StatePreCandidate
 	r.logger.Infof("%x became pre-candidate at term %d", r.id, r.Term)
@@ -682,7 +755,6 @@ func (r *raft) Step(m pb.Message) error {
 	case m.Term == 0:
 		// local message
 	case m.Term > r.Term:
-		lead := m.From
 		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
@@ -693,7 +765,6 @@ func (r *raft) Step(m pb.Message) error {
 					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
 			}
-			lead = None
 		}
 		switch {
 		case m.Type == pb.MsgPreVote:
@@ -707,7 +778,11 @@ func (r *raft) Step(m pb.Message) error {
 		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)
-			r.becomeFollower(m.Term, lead)
+			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:
@@ -757,12 +832,27 @@ func (r *raft) Step(m pb.Message) error {
 		}
 
 	case pb.MsgVote, pb.MsgPreVote:
+		if r.isLearner {
+			// TODO: learner may need to vote, in case of node down when confchange.
+			r.logger.Infof("%x [logterm: %d, index: %d, vote: %x] ignored %s from %x [logterm: %d, index: %d] at term %d: learner can not vote",
+				r.id, r.raftLog.lastTerm(), r.raftLog.lastIndex(), r.Vote, m.Type, m.From, m.LogTerm, m.Index, r.Term)
+			return nil
+		}
 		// The m.Term > r.Term clause is for MsgPreVote. For MsgVote m.Term should
 		// always equal r.Term.
 		if (r.Vote == None || m.Term > r.Term || r.Vote == m.From) && r.raftLog.isUpToDate(m.Index, m.LogTerm) {
 			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)
-			r.send(pb.Message{To: m.From, Type: voteRespMsgType(m.Type)})
+			// 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 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
@@ -771,7 +861,7 @@ func (r *raft) Step(m pb.Message) error {
 		} 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, Type: voteRespMsgType(m.Type), Reject: true})
+			r.send(pb.Message{To: m.From, Term: r.Term, Type: voteRespMsgType(m.Type), Reject: true})
 		}
 
 	default:
@@ -836,10 +926,7 @@ func stepLeader(r *raft, m pb.Message) {
 				r.readOnly.addRequest(r.raftLog.committed, m)
 				r.bcastHeartbeatWithCtx(m.Entries[0].Data)
 			case ReadOnlyLeaseBased:
-				var ri uint64
-				if r.checkQuorum {
-					ri = r.raftLog.committed
-				}
+				ri := r.raftLog.committed
 				if m.From == None || m.From == r.id { // from local member
 					r.readStates = append(r.readStates, ReadState{Index: r.raftLog.committed, RequestCtx: m.Entries[0].Data})
 				} else {
@@ -854,8 +941,8 @@ func stepLeader(r *raft, m pb.Message) {
 	}
 
 	// All other message types require a progress for m.From (pr).
-	pr, prOk := r.prs[m.From]
-	if !prOk {
+	pr := r.getProgress(m.From)
+	if pr == nil {
 		r.logger.Debugf("%x no progress available for %x", r.id, m.From)
 		return
 	}
@@ -954,6 +1041,10 @@ func stepLeader(r *raft, m pb.Message) {
 		}
 		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
+		}
 		leadTransferee := m.From
 		lastLeadTransferee := r.leadTransferee
 		if lastLeadTransferee != None {
@@ -1033,6 +1124,9 @@ func stepFollower(r *raft, m pb.Message) {
 		if r.lead == None {
 			r.logger.Infof("%x no leader at term %d; dropping proposal", r.id, r.Term)
 			return
+		} 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
 		}
 		m.To = r.lead
 		r.send(m)
@@ -1127,20 +1221,37 @@ func (r *raft) restore(s pb.Snapshot) bool {
 		return false
 	}
 
+	// The normal peer can't become learner.
+	if !r.isLearner {
+		for _, id := range s.Metadata.ConfState.Learners {
+			if id == r.id {
+				r.logger.Errorf("%x can't become learner when restores snapshot [index: %d, term: %d]", r.id, s.Metadata.Index, s.Metadata.Term)
+				return false
+			}
+		}
+	}
+
 	r.logger.Infof("%x [commit: %d, lastindex: %d, lastterm: %d] starts to restore snapshot [index: %d, term: %d]",
 		r.id, r.raftLog.committed, r.raftLog.lastIndex(), r.raftLog.lastTerm(), s.Metadata.Index, s.Metadata.Term)
 
 	r.raftLog.restore(s)
 	r.prs = make(map[uint64]*Progress)
-	for _, n := range s.Metadata.ConfState.Nodes {
+	r.learnerPrs = make(map[uint64]*Progress)
+	r.restoreNode(s.Metadata.ConfState.Nodes, false)
+	r.restoreNode(s.Metadata.ConfState.Learners, true)
+	return true
+}
+
+func (r *raft) restoreNode(nodes []uint64, isLearner bool) {
+	for _, n := range nodes {
 		match, next := uint64(0), r.raftLog.lastIndex()+1
 		if n == r.id {
 			match = next - 1
+			r.isLearner = isLearner
 		}
-		r.setProgress(n, match, next)
-		r.logger.Infof("%x restored progress of %x [%s]", r.id, n, r.prs[n])
+		r.setProgress(n, match, next, isLearner)
+		r.logger.Infof("%x restored progress of %x [%s]", r.id, n, r.getProgress(n))
 	}
-	return true
 }
 
 // promotable indicates whether state machine can be promoted to leader,
@@ -1151,18 +1262,46 @@ func (r *raft) promotable() bool {
 }
 
 func (r *raft) addNode(id uint64) {
+	r.addNodeOrLearnerNode(id, false)
+}
+
+func (r *raft) addLearner(id uint64) {
+	r.addNodeOrLearnerNode(id, true)
+}
+
+func (r *raft) addNodeOrLearnerNode(id uint64, isLearner bool) {
 	r.pendingConf = false
-	if _, ok := r.prs[id]; ok {
-		// Ignore any redundant addNode calls (which can happen because the
-		// initial bootstrapping entries are applied twice).
-		return
+	pr := r.getProgress(id)
+	if pr == nil {
+		r.setProgress(id, 0, r.raftLog.lastIndex()+1, isLearner)
+	} else {
+		if isLearner && !pr.IsLearner {
+			// can only change Learner to Voter
+			r.logger.Infof("%x ignored addLeaner: do not support changing %x from raft peer to learner.", r.id, id)
+			return
+		}
+
+		if isLearner == pr.IsLearner {
+			// Ignore any redundant addNode calls (which can happen because the
+			// initial bootstrapping entries are applied twice).
+			return
+		}
+
+		// change Learner to Voter, use origin Learner progress
+		delete(r.learnerPrs, id)
+		pr.IsLearner = false
+		r.prs[id] = pr
+	}
+
+	if r.id == id {
+		r.isLearner = isLearner
 	}
 
-	r.setProgress(id, 0, r.raftLog.lastIndex()+1)
 	// When a node is first added, we should mark it as recently active.
 	// Otherwise, CheckQuorum may cause us to step down if it is invoked
 	// before the added node has a chance to communicate with us.
-	r.prs[id].RecentActive = true
+	pr = r.getProgress(id)
+	pr.RecentActive = true
 }
 
 func (r *raft) removeNode(id uint64) {
@@ -1170,7 +1309,7 @@ func (r *raft) removeNode(id uint64) {
 	r.pendingConf = false
 
 	// do not try to commit or abort transferring if there is no nodes in the cluster.
-	if len(r.prs) == 0 {
+	if len(r.prs) == 0 && len(r.learnerPrs) == 0 {
 		return
 	}
 
@@ -1187,12 +1326,22 @@ func (r *raft) removeNode(id uint64) {
 
 func (r *raft) resetPendingConf() { r.pendingConf = false }
 
-func (r *raft) setProgress(id, match, next uint64) {
-	r.prs[id] = &Progress{Next: next, Match: match, ins: newInflights(r.maxInflight)}
+func (r *raft) setProgress(id, match, next uint64, isLearner bool) {
+	if !isLearner {
+		delete(r.learnerPrs, id)
+		r.prs[id] = &Progress{Next: next, Match: match, ins: newInflights(r.maxInflight)}
+		return
+	}
+
+	if _, ok := r.prs[id]; ok {
+		panic(fmt.Sprintf("%x unexpected changing from voter to learner for %x", r.id, id))
+	}
+	r.learnerPrs[id] = &Progress{Next: next, Match: match, ins: newInflights(r.maxInflight), IsLearner: true}
 }
 
 func (r *raft) delProgress(id uint64) {
 	delete(r.prs, id)
+	delete(r.learnerPrs, id)
 }
 
 func (r *raft) loadState(state pb.HardState) {
@@ -1222,18 +1371,18 @@ func (r *raft) resetRandomizedElectionTimeout() {
 func (r *raft) checkQuorumActive() bool {
 	var act int
 
-	for id := range r.prs {
+	r.forEachProgress(func(id uint64, pr *Progress) {
 		if id == r.id { // self is always active
 			act++
-			continue
+			return
 		}
 
-		if r.prs[id].RecentActive {
+		if pr.RecentActive && !pr.IsLearner {
 			act++
 		}
 
-		r.prs[id].RecentActive = false
-	}
+		pr.RecentActive = false
+	})
 
 	return act >= r.quorum()
 }

vendor/github.com/coreos/etcd/raft/raftpb/BUILD

@@ -6,7 +6,10 @@ go_library(
     importmap = "k8s.io/kubernetes/vendor/github.com/coreos/etcd/raft/raftpb",
     importpath = "github.com/coreos/etcd/raft/raftpb",
     visibility = ["//visibility:public"],
-    deps = ["//vendor/github.com/golang/protobuf/proto:go_default_library"],
+    deps = [
+        "//vendor/github.com/gogo/protobuf/gogoproto:go_default_library",
+        "//vendor/github.com/golang/protobuf/proto:go_default_library",
+    ],
 )
 
 filegroup(

vendor/github.com/coreos/etcd/raft/raftpb/raft.pb.go

@@ -1,6 +1,5 @@
-// Code generated by protoc-gen-gogo.
+// Code generated by protoc-gen-gogo. DO NOT EDIT.
 // source: raft.proto
-// DO NOT EDIT!
 
 /*
 	Package raftpb is a generated protocol buffer package.
@@ -26,6 +25,8 @@ import (
 
 	math "math"
 
+	_ "github.com/gogo/protobuf/gogoproto"
+
 	io "io"
 )
 
@@ -162,20 +163,23 @@ func (MessageType) EnumDescriptor() ([]byte, []int) { return fileDescriptorRaft,
 type ConfChangeType int32
 
 const (
-	ConfChangeAddNode    ConfChangeType = 0
-	ConfChangeRemoveNode ConfChangeType = 1
-	ConfChangeUpdateNode ConfChangeType = 2
+	ConfChangeAddNode        ConfChangeType = 0
+	ConfChangeRemoveNode     ConfChangeType = 1
+	ConfChangeUpdateNode     ConfChangeType = 2
+	ConfChangeAddLearnerNode ConfChangeType = 3
 )
 
 var ConfChangeType_name = map[int32]string{
 	0: "ConfChangeAddNode",
 	1: "ConfChangeRemoveNode",
 	2: "ConfChangeUpdateNode",
+	3: "ConfChangeAddLearnerNode",
 }
 var ConfChangeType_value = map[string]int32{
-	"ConfChangeAddNode":    0,
-	"ConfChangeRemoveNode": 1,
-	"ConfChangeUpdateNode": 2,
+	"ConfChangeAddNode":        0,
+	"ConfChangeRemoveNode":     1,
+	"ConfChangeUpdateNode":     2,
+	"ConfChangeAddLearnerNode": 3,
 }
 
 func (x ConfChangeType) Enum() *ConfChangeType {
@@ -267,6 +271,7 @@ func (*HardState) Descriptor() ([]byte, []int) { return fileDescriptorRaft, []in
 
 type ConfState struct {
 	Nodes            []uint64 `protobuf:"varint,1,rep,name=nodes" json:"nodes,omitempty"`
+	Learners         []uint64 `protobuf:"varint,2,rep,name=learners" json:"learners,omitempty"`
 	XXX_unrecognized []byte   `json:"-"`
 }
 
@@ -537,6 +542,13 @@ func (m *ConfState) MarshalTo(dAtA []byte) (int, error) {
 			i = encodeVarintRaft(dAtA, i, uint64(num))
 		}
 	}
+	if len(m.Learners) > 0 {
+		for _, num := range m.Learners {
+			dAtA[i] = 0x10
+			i++
+			i = encodeVarintRaft(dAtA, i, uint64(num))
+		}
+	}
 	if m.XXX_unrecognized != nil {
 		i += copy(dAtA[i:], m.XXX_unrecognized)
 	}
@@ -579,24 +591,6 @@ func (m *ConfChange) MarshalTo(dAtA []byte) (int, error) {
 	return i, nil
 }
 
-func encodeFixed64Raft(dAtA []byte, offset int, v uint64) int {
-	dAtA[offset] = uint8(v)
-	dAtA[offset+1] = uint8(v >> 8)
-	dAtA[offset+2] = uint8(v >> 16)
-	dAtA[offset+3] = uint8(v >> 24)
-	dAtA[offset+4] = uint8(v >> 32)
-	dAtA[offset+5] = uint8(v >> 40)
-	dAtA[offset+6] = uint8(v >> 48)
-	dAtA[offset+7] = uint8(v >> 56)
-	return offset + 8
-}
-func encodeFixed32Raft(dAtA []byte, offset int, v uint32) int {
-	dAtA[offset] = uint8(v)
-	dAtA[offset+1] = uint8(v >> 8)
-	dAtA[offset+2] = uint8(v >> 16)
-	dAtA[offset+3] = uint8(v >> 24)
-	return offset + 4
-}
 func encodeVarintRaft(dAtA []byte, offset int, v uint64) int {
 	for v >= 1<<7 {
 		dAtA[offset] = uint8(v&0x7f | 0x80)
@@ -700,6 +694,11 @@ func (m *ConfState) Size() (n int) {
 			n += 1 + sovRaft(uint64(e))
 		}
 	}
+	if len(m.Learners) > 0 {
+		for _, e := range m.Learners {
+			n += 1 + sovRaft(uint64(e))
+		}
+	}
 	if m.XXX_unrecognized != nil {
 		n += len(m.XXX_unrecognized)
 	}
@@ -1619,6 +1618,68 @@ func (m *ConfState) Unmarshal(dAtA []byte) error {
 			} else {
 				return fmt.Errorf("proto: wrong wireType = %d for field Nodes", wireType)
 			}
+		case 2:
+			if wireType == 0 {
+				var v uint64
+				for shift := uint(0); ; shift += 7 {
+					if shift >= 64 {
+						return ErrIntOverflowRaft
+					}
+					if iNdEx >= l {
+						return io.ErrUnexpectedEOF
+					}
+					b := dAtA[iNdEx]
+					iNdEx++
+					v |= (uint64(b) & 0x7F) << shift
+					if b < 0x80 {
+						break
+					}
+				}
+				m.Learners = append(m.Learners, v)
+			} else if wireType == 2 {
+				var packedLen int
+				for shift := uint(0); ; shift += 7 {
+					if shift >= 64 {
+						return ErrIntOverflowRaft
+					}
+					if iNdEx >= l {
+						return io.ErrUnexpectedEOF
+					}
+					b := dAtA[iNdEx]
+					iNdEx++
+					packedLen |= (int(b) & 0x7F) << shift
+					if b < 0x80 {
+						break
+					}
+				}
+				if packedLen < 0 {
+					return ErrInvalidLengthRaft
+				}
+				postIndex := iNdEx + packedLen
+				if postIndex > l {
+					return io.ErrUnexpectedEOF
+				}
+				for iNdEx < postIndex {
+					var v uint64
+					for shift := uint(0); ; shift += 7 {
+						if shift >= 64 {
+							return ErrIntOverflowRaft
+						}
+						if iNdEx >= l {
+							return io.ErrUnexpectedEOF
+						}
+						b := dAtA[iNdEx]
+						iNdEx++
+						v |= (uint64(b) & 0x7F) << shift
+						if b < 0x80 {
+							break
+						}
+					}
+					m.Learners = append(m.Learners, v)
+				}
+			} else {
+				return fmt.Errorf("proto: wrong wireType = %d for field Learners", wireType)
+			}
 		default:
 			iNdEx = preIndex
 			skippy, err := skipRaft(dAtA[iNdEx:])
@@ -1888,55 +1949,56 @@ var (
 func init() { proto.RegisterFile("raft.proto", fileDescriptorRaft) }
 
 var fileDescriptorRaft = []byte{
-	// 790 bytes of a gzipped FileDescriptorProto
-	0x1f, 0x8b, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, 0xff, 0x64, 0x54, 0xcd, 0x6e, 0xdb, 0x46,
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-	0x01, 0x41, 0x3a, 0x06, 0x00, 0x00,
+	// 815 bytes of a gzipped FileDescriptorProto
+	0x1f, 0x8b, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, 0xff, 0x64, 0x54, 0xcd, 0x6e, 0x23, 0x45,
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+	0x1a, 0xf7, 0x0f, 0x23, 0xef, 0xfd, 0xc3, 0xc8, 0xfb, 0xf7, 0x61, 0xe4, 0xfd, 0xf9, 0xdf, 0xa8,
+	0xf1, 0x7f, 0x00, 0x00, 0x00, 0xff, 0xff, 0x86, 0x52, 0x5b, 0xe0, 0x74, 0x06, 0x00, 0x00,
 }

vendor/github.com/coreos/etcd/raft/raftpb/raft.proto

@@ -76,13 +76,15 @@ message HardState {
 }
 
 message ConfState {
-	repeated uint64 nodes = 1;
+	repeated uint64 nodes    = 1;
+	repeated uint64 learners = 2;
 }
 
 enum ConfChangeType {
-	ConfChangeAddNode    = 0;
-	ConfChangeRemoveNode = 1;
-	ConfChangeUpdateNode = 2;
+	ConfChangeAddNode        = 0;
+	ConfChangeRemoveNode     = 1;
+	ConfChangeUpdateNode     = 2;
+	ConfChangeAddLearnerNode = 3;
 }
 
 message ConfChange {

vendor/github.com/coreos/etcd/raft/rawnode.go

@@ -175,6 +175,8 @@ func (rn *RawNode) ApplyConfChange(cc pb.ConfChange) *pb.ConfState {
 	switch cc.Type {
 	case pb.ConfChangeAddNode:
 		rn.raft.addNode(cc.NodeID)
+	case pb.ConfChangeAddLearnerNode:
+		rn.raft.addLearner(cc.NodeID)
 	case pb.ConfChangeRemoveNode:
 		rn.raft.removeNode(cc.NodeID)
 	case pb.ConfChangeUpdateNode:
@@ -191,7 +193,7 @@ func (rn *RawNode) Step(m pb.Message) error {
 	if IsLocalMsg(m.Type) {
 		return ErrStepLocalMsg
 	}
-	if _, ok := rn.raft.prs[m.From]; ok || !IsResponseMsg(m.Type) {
+	if pr := rn.raft.getProgress(m.From); pr != nil || !IsResponseMsg(m.Type) {
 		return rn.raft.Step(m)
 	}
 	return ErrStepPeerNotFound

vendor/github.com/coreos/etcd/raft/read_only.go

@@ -18,7 +18,7 @@ import pb "github.com/coreos/etcd/raft/raftpb"
 
 // ReadState provides state for read only query.
 // It's caller's responsibility to call ReadIndex first before getting
-// this state from ready, It's also caller's duty to differentiate if this
+// this state from ready, it's also caller's duty to differentiate if this
 // state is what it requests through RequestCtx, eg. given a unique id as
 // RequestCtx
 type ReadState struct {

vendor/github.com/coreos/etcd/raft/status.go

@@ -28,11 +28,17 @@ type Status struct {
 
 	Applied  uint64
 	Progress map[uint64]Progress
+
+	LeadTransferee uint64
 }
 
 // getStatus gets a copy of the current raft status.
 func getStatus(r *raft) Status {
-	s := Status{ID: r.id}
+	s := Status{
+		ID:             r.id,
+		LeadTransferee: r.leadTransferee,
+	}
+
 	s.HardState = r.hardState()
 	s.SoftState = *r.softState()
 
@@ -43,6 +49,10 @@ func getStatus(r *raft) Status {
 		for id, p := range r.prs {
 			s.Progress[id] = *p
 		}
+
+		for id, p := range r.learnerPrs {
+			s.Progress[id] = *p
+		}
 	}
 
 	return s
@@ -51,19 +61,21 @@ func getStatus(r *raft) Status {
 // MarshalJSON translates the raft status into JSON.
 // TODO: try to simplify this by introducing ID type into raft
 func (s Status) MarshalJSON() ([]byte, error) {
-	j := fmt.Sprintf(`{"id":"%x","term":%d,"vote":"%x","commit":%d,"lead":"%x","raftState":%q,"progress":{`,
-		s.ID, s.Term, s.Vote, s.Commit, s.Lead, s.RaftState)
+	j := fmt.Sprintf(`{"id":"%x","term":%d,"vote":"%x","commit":%d,"lead":"%x","raftState":%q,"applied":%d,"progress":{`,
+		s.ID, s.Term, s.Vote, s.Commit, s.Lead, s.RaftState, s.Applied)
 
 	if len(s.Progress) == 0 {
-		j += "}}"
+		j += "},"
 	} else {
 		for k, v := range s.Progress {
 			subj := fmt.Sprintf(`"%x":{"match":%d,"next":%d,"state":%q},`, k, v.Match, v.Next, v.State)
 			j += subj
 		}
 		// remove the trailing ","
-		j = j[:len(j)-1] + "}}"
+		j = j[:len(j)-1] + "},"
 	}
+
+	j += fmt.Sprintf(`"leadtransferee":"%x"}`, s.LeadTransferee)
 	return []byte(j), nil
 }