diff --git a/vendor/go.etcd.io/raft/v3/node.go b/vendor/go.etcd.io/raft/v3/node.go
new file mode 100644
index 0000000..e2a261c
--- /dev/null
+++ b/vendor/go.etcd.io/raft/v3/node.go
@@ -0,0 +1,610 @@
+// 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 (
+	"context"
+	"errors"
+
+	pb "go.etcd.io/raft/v3/raftpb"
+)
+
+type SnapshotStatus int
+
+const (
+	SnapshotFinish  SnapshotStatus = 1
+	SnapshotFailure SnapshotStatus = 2
+)
+
+var (
+	emptyState = pb.HardState{}
+
+	// ErrStopped is returned by methods on Nodes that have been stopped.
+	ErrStopped = errors.New("raft: stopped")
+)
+
+// SoftState provides state that is useful for logging and debugging.
+// The state is volatile and does not need to be persisted to the WAL.
+type SoftState struct {
+	Lead      uint64 // must use atomic operations to access; keep 64-bit aligned.
+	RaftState StateType
+}
+
+func (a *SoftState) equal(b *SoftState) bool {
+	return a.Lead == b.Lead && a.RaftState == b.RaftState
+}
+
+// Ready encapsulates the entries and messages that are ready to read,
+// be saved to stable storage, committed or sent to other peers.
+// All fields in Ready are read-only.
+type Ready struct {
+	// The current volatile state of a Node.
+	// SoftState will be nil if there is no update.
+	// It is not required to consume or store SoftState.
+	*SoftState
+
+	// The current state of a Node to be saved to stable storage BEFORE
+	// Messages are sent.
+	//
+	// HardState will be equal to empty state if there is no update.
+	//
+	// If async storage writes are enabled, this field does not need to be acted
+	// on immediately. It will be reflected in a MsgStorageAppend message in the
+	// Messages slice.
+	pb.HardState
+
+	// ReadStates can be used for node to serve linearizable read requests locally
+	// when its applied index is greater than the index in ReadState.
+	// Note that the readState will be returned when raft receives msgReadIndex.
+	// The returned is only valid for the request that requested to read.
+	ReadStates []ReadState
+
+	// Entries specifies entries to be saved to stable storage BEFORE
+	// Messages are sent.
+	//
+	// If async storage writes are enabled, this field does not need to be acted
+	// on immediately. It will be reflected in a MsgStorageAppend message in the
+	// Messages slice.
+	Entries []pb.Entry
+
+	// Snapshot specifies the snapshot to be saved to stable storage.
+	//
+	// If async storage writes are enabled, this field does not need to be acted
+	// on immediately. It will be reflected in a MsgStorageAppend message in the
+	// Messages slice.
+	Snapshot pb.Snapshot
+
+	// CommittedEntries specifies entries to be committed to a
+	// store/state-machine. These have previously been appended to stable
+	// storage.
+	//
+	// If async storage writes are enabled, this field does not need to be acted
+	// on immediately. It will be reflected in a MsgStorageApply message in the
+	// Messages slice.
+	CommittedEntries []pb.Entry
+
+	// Messages specifies outbound messages.
+	//
+	// If async storage writes are not enabled, these messages must be sent
+	// AFTER Entries are appended to stable storage.
+	//
+	// If async storage writes are enabled, these messages can be sent
+	// immediately as the messages that have the completion of the async writes
+	// as a precondition are attached to the individual MsgStorage{Append,Apply}
+	// messages instead.
+	//
+	// If it contains a MsgSnap message, the application MUST report back to raft
+	// when the snapshot has been received or has failed by calling ReportSnapshot.
+	Messages []pb.Message
+
+	// MustSync indicates whether the HardState and Entries must be durably
+	// written to disk or if a non-durable write is permissible.
+	MustSync bool
+}
+
+func isHardStateEqual(a, b pb.HardState) bool {
+	return a.Term == b.Term && a.Vote == b.Vote && a.Commit == b.Commit
+}
+
+// IsEmptyHardState returns true if the given HardState is empty.
+func IsEmptyHardState(st pb.HardState) bool {
+	return isHardStateEqual(st, emptyState)
+}
+
+// IsEmptySnap returns true if the given Snapshot is empty.
+func IsEmptySnap(sp pb.Snapshot) bool {
+	return sp.Metadata.Index == 0
+}
+
+// Node represents a node in a raft cluster.
+type Node interface {
+	// Tick increments the internal logical clock for the Node by a single tick. Election
+	// timeouts and heartbeat timeouts are in units of ticks.
+	Tick()
+	// Campaign causes the Node to transition to candidate state and start campaigning to become leader.
+	Campaign(ctx context.Context) error
+	// Propose proposes that data be appended to the log. Note that proposals can be lost without
+	// notice, therefore it is user's job to ensure proposal retries.
+	Propose(ctx context.Context, data []byte) error
+	// ProposeConfChange proposes a configuration change. Like any proposal, the
+	// configuration change may be dropped with or without an error being
+	// returned. In particular, configuration changes are dropped unless the
+	// leader has certainty that there is no prior unapplied configuration
+	// change in its log.
+	//
+	// The method accepts either a pb.ConfChange (deprecated) or pb.ConfChangeV2
+	// message. The latter allows arbitrary configuration changes via joint
+	// consensus, notably including replacing a voter. Passing a ConfChangeV2
+	// message is only allowed if all Nodes participating in the cluster run a
+	// version of this library aware of the V2 API. See pb.ConfChangeV2 for
+	// usage details and semantics.
+	ProposeConfChange(ctx context.Context, cc pb.ConfChangeI) error
+
+	// Step advances the state machine using the given message. ctx.Err() will be returned, if any.
+	Step(ctx context.Context, msg pb.Message) error
+
+	// Ready returns a channel that returns the current point-in-time state.
+	// Users of the Node must call Advance after retrieving the state returned by Ready (unless
+	// async storage writes is enabled, in which case it should never be called).
+	//
+	// NOTE: No committed entries from the next Ready may be applied until all committed entries
+	// and snapshots from the previous one have finished.
+	Ready() <-chan Ready
+
+	// Advance notifies the Node that the application has saved progress up to the last Ready.
+	// It prepares the node to return the next available Ready.
+	//
+	// The application should generally call Advance after it applies the entries in last Ready.
+	//
+	// However, as an optimization, the application may call Advance while it is applying the
+	// commands. For example. when the last Ready contains a snapshot, the application might take
+	// a long time to apply the snapshot data. To continue receiving Ready without blocking raft
+	// progress, it can call Advance before finishing applying the last ready.
+	//
+	// NOTE: Advance must not be called when using AsyncStorageWrites. Response messages from the
+	// local append and apply threads take its place.
+	Advance()
+	// ApplyConfChange applies a config change (previously passed to
+	// ProposeConfChange) to the node. This must be called whenever a config
+	// change is observed in Ready.CommittedEntries, except when the app decides
+	// to reject the configuration change (i.e. treats it as a noop instead), in
+	// which case it must not be called.
+	//
+	// Returns an opaque non-nil ConfState protobuf which must be recorded in
+	// snapshots.
+	ApplyConfChange(cc pb.ConfChangeI) *pb.ConfState
+
+	// TransferLeadership attempts to transfer leadership to the given transferee.
+	TransferLeadership(ctx context.Context, lead, transferee uint64)
+
+	// ForgetLeader forgets a follower's current leader, changing it to None. It
+	// remains a leaderless follower in the current term, without campaigning.
+	//
+	// This is useful with PreVote+CheckQuorum, where followers will normally not
+	// grant pre-votes if they've heard from the leader in the past election
+	// timeout interval. Leaderless followers can grant pre-votes immediately, so
+	// if a quorum of followers have strong reason to believe the leader is dead
+	// (for example via a side-channel or external failure detector) and forget it
+	// then they can elect a new leader immediately, without waiting out the
+	// election timeout. They will also revert to normal followers if they hear
+	// from the leader again, or transition to candidates on an election timeout.
+	//
+	// For example, consider a three-node cluster where 1 is the leader and 2+3
+	// have just received a heartbeat from it. If 2 and 3 believe the leader has
+	// now died (maybe they know that an orchestration system shut down 1's VM),
+	// we can instruct 2 to forget the leader and 3 to campaign. 2 will then be
+	// able to grant 3's pre-vote and elect 3 as leader immediately (normally 2
+	// would reject the vote until an election timeout passes because it has heard
+	// from the leader recently). However, 3 can not campaign unilaterally, a
+	// quorum have to agree that the leader is dead, which avoids disrupting the
+	// leader if individual nodes are wrong about it being dead.
+	//
+	// This does nothing with ReadOnlyLeaseBased, since it would allow a new
+	// leader to be elected without the old leader knowing.
+	ForgetLeader(ctx context.Context) error
+
+	// ReadIndex request a read state. The read state will be set in the ready.
+	// Read state has a read index. Once the application advances further than the read
+	// index, any linearizable read requests issued before the read request can be
+	// processed safely. The read state will have the same rctx attached.
+	// Note that request can be lost without notice, therefore it is user's job
+	// to ensure read index retries.
+	ReadIndex(ctx context.Context, rctx []byte) error
+
+	// Status returns the current status of the raft state machine.
+	Status() Status
+	// ReportUnreachable reports the given node is not reachable for the last send.
+	ReportUnreachable(id uint64)
+	// ReportSnapshot reports the status of the sent snapshot. The id is the raft ID of the follower
+	// who is meant to receive the snapshot, and the status is SnapshotFinish or SnapshotFailure.
+	// Calling ReportSnapshot with SnapshotFinish is a no-op. But, any failure in applying a
+	// snapshot (for e.g., while streaming it from leader to follower), should be reported to the
+	// leader with SnapshotFailure. When leader sends a snapshot to a follower, it pauses any raft
+	// log probes until the follower can apply the snapshot and advance its state. If the follower
+	// can't do that, for e.g., due to a crash, it could end up in a limbo, never getting any
+	// updates from the leader. Therefore, it is crucial that the application ensures that any
+	// failure in snapshot sending is caught and reported back to the leader; so it can resume raft
+	// log probing in the follower.
+	ReportSnapshot(id uint64, status SnapshotStatus)
+	// Stop performs any necessary termination of the Node.
+	Stop()
+}
+
+type Peer struct {
+	ID      uint64
+	Context []byte
+}
+
+func setupNode(c *Config, peers []Peer) *node {
+	if len(peers) == 0 {
+		panic("no peers given; use RestartNode instead")
+	}
+	rn, err := NewRawNode(c)
+	if err != nil {
+		panic(err)
+	}
+	err = rn.Bootstrap(peers)
+	if err != nil {
+		c.Logger.Warningf("error occurred during starting a new node: %v", err)
+	}
+
+	n := newNode(rn)
+	return &n
+}
+
+// StartNode returns a new Node given configuration and a list of raft peers.
+// It appends a ConfChangeAddNode entry for each given peer to the initial log.
+//
+// Peers must not be zero length; call RestartNode in that case.
+func StartNode(c *Config, peers []Peer) Node {
+	n := setupNode(c, peers)
+	go n.run()
+	return n
+}
+
+// RestartNode is similar to StartNode but does not take a list of peers.
+// The current membership of the cluster will be restored from the Storage.
+// If the caller has an existing state machine, pass in the last log index that
+// has been applied to it; otherwise use zero.
+func RestartNode(c *Config) Node {
+	rn, err := NewRawNode(c)
+	if err != nil {
+		panic(err)
+	}
+	n := newNode(rn)
+	go n.run()
+	return &n
+}
+
+type msgWithResult struct {
+	m      pb.Message
+	result chan error
+}
+
+// node is the canonical implementation of the Node interface
+type node struct {
+	propc      chan msgWithResult
+	recvc      chan pb.Message
+	confc      chan pb.ConfChangeV2
+	confstatec chan pb.ConfState
+	readyc     chan Ready
+	advancec   chan struct{}
+	tickc      chan struct{}
+	done       chan struct{}
+	stop       chan struct{}
+	status     chan chan Status
+
+	rn *RawNode
+}
+
+func newNode(rn *RawNode) node {
+	return node{
+		propc:      make(chan msgWithResult),
+		recvc:      make(chan pb.Message),
+		confc:      make(chan pb.ConfChangeV2),
+		confstatec: make(chan pb.ConfState),
+		readyc:     make(chan Ready),
+		advancec:   make(chan struct{}),
+		// make tickc a buffered chan, so raft node can buffer some ticks when the node
+		// is busy processing raft messages. Raft node will resume process buffered
+		// ticks when it becomes idle.
+		tickc:  make(chan struct{}, 128),
+		done:   make(chan struct{}),
+		stop:   make(chan struct{}),
+		status: make(chan chan Status),
+		rn:     rn,
+	}
+}
+
+func (n *node) Stop() {
+	select {
+	case n.stop <- struct{}{}:
+		// Not already stopped, so trigger it
+	case <-n.done:
+		// Node has already been stopped - no need to do anything
+		return
+	}
+	// Block until the stop has been acknowledged by run()
+	<-n.done
+}
+
+func (n *node) run() {
+	var propc chan msgWithResult
+	var readyc chan Ready
+	var advancec chan struct{}
+	var rd Ready
+
+	r := n.rn.raft
+
+	lead := None
+
+	for {
+		if advancec == nil && n.rn.HasReady() {
+			// Populate a Ready. Note that this Ready is not guaranteed to
+			// actually be handled. We will arm readyc, but there's no guarantee
+			// that we will actually send on it. It's possible that we will
+			// service another channel instead, loop around, and then populate
+			// the Ready again. We could instead force the previous Ready to be
+			// handled first, but it's generally good to emit larger Readys plus
+			// it simplifies testing (by emitting less frequently and more
+			// predictably).
+			rd = n.rn.readyWithoutAccept()
+			readyc = n.readyc
+		}
+
+		if lead != r.lead {
+			if r.hasLeader() {
+				if lead == None {
+					r.logger.Infof("raft.node: %x elected leader %x at term %d", r.id, r.lead, r.Term)
+				} else {
+					r.logger.Infof("raft.node: %x changed leader from %x to %x at term %d", r.id, lead, r.lead, r.Term)
+				}
+				propc = n.propc
+			} else {
+				r.logger.Infof("raft.node: %x lost leader %x at term %d", r.id, lead, r.Term)
+				propc = nil
+			}
+			lead = r.lead
+		}
+
+		select {
+		// TODO: maybe buffer the config propose if there exists one (the way
+		// described in raft dissertation)
+		// Currently it is dropped in Step silently.
+		case pm := <-propc:
+			m := pm.m
+			m.From = r.id
+			err := r.Step(m)
+			if pm.result != nil {
+				pm.result <- err
+				close(pm.result)
+			}
+		case m := <-n.recvc:
+			if IsResponseMsg(m.Type) && !IsLocalMsgTarget(m.From) && r.trk.Progress[m.From] == nil {
+				// Filter out response message from unknown From.
+				break
+			}
+			r.Step(m)
+		case cc := <-n.confc:
+			_, okBefore := r.trk.Progress[r.id]
+			cs := r.applyConfChange(cc)
+			// If the node was removed, block incoming proposals. Note that we
+			// only do this if the node was in the config before. Nodes may be
+			// a member of the group without knowing this (when they're catching
+			// up on the log and don't have the latest config) and we don't want
+			// to block the proposal channel in that case.
+			//
+			// NB: propc is reset when the leader changes, which, if we learn
+			// about it, sort of implies that we got readded, maybe? This isn't
+			// very sound and likely has bugs.
+			if _, okAfter := r.trk.Progress[r.id]; okBefore && !okAfter {
+				var found bool
+				for _, sl := range [][]uint64{cs.Voters, cs.VotersOutgoing} {
+					for _, id := range sl {
+						if id == r.id {
+							found = true
+							break
+						}
+					}
+					if found {
+						break
+					}
+				}
+				if !found {
+					propc = nil
+				}
+			}
+			select {
+			case n.confstatec <- cs:
+			case <-n.done:
+			}
+		case <-n.tickc:
+			n.rn.Tick()
+		case readyc <- rd:
+			n.rn.acceptReady(rd)
+			if !n.rn.asyncStorageWrites {
+				advancec = n.advancec
+			} else {
+				rd = Ready{}
+			}
+			readyc = nil
+		case <-advancec:
+			n.rn.Advance(rd)
+			rd = Ready{}
+			advancec = nil
+		case c := <-n.status:
+			c <- getStatus(r)
+		case <-n.stop:
+			close(n.done)
+			return
+		}
+	}
+}
+
+// Tick increments the internal logical clock for this Node. Election timeouts
+// and heartbeat timeouts are in units of ticks.
+func (n *node) Tick() {
+	select {
+	case n.tickc <- struct{}{}:
+	case <-n.done:
+	default:
+		n.rn.raft.logger.Warningf("%x A tick missed to fire. Node blocks too long!", n.rn.raft.id)
+	}
+}
+
+func (n *node) Campaign(ctx context.Context) error { return n.step(ctx, pb.Message{Type: pb.MsgHup}) }
+
+func (n *node) Propose(ctx context.Context, data []byte) error {
+	return n.stepWait(ctx, pb.Message{Type: pb.MsgProp, Entries: []pb.Entry{{Data: data}}})
+}
+
+func (n *node) Step(ctx context.Context, m pb.Message) error {
+	// Ignore unexpected local messages receiving over network.
+	if IsLocalMsg(m.Type) && !IsLocalMsgTarget(m.From) {
+		// TODO: return an error?
+		return nil
+	}
+	return n.step(ctx, m)
+}
+
+func confChangeToMsg(c pb.ConfChangeI) (pb.Message, error) {
+	typ, data, err := pb.MarshalConfChange(c)
+	if err != nil {
+		return pb.Message{}, err
+	}
+	return pb.Message{Type: pb.MsgProp, Entries: []pb.Entry{{Type: typ, Data: data}}}, nil
+}
+
+func (n *node) ProposeConfChange(ctx context.Context, cc pb.ConfChangeI) error {
+	msg, err := confChangeToMsg(cc)
+	if err != nil {
+		return err
+	}
+	return n.Step(ctx, msg)
+}
+
+func (n *node) step(ctx context.Context, m pb.Message) error {
+	return n.stepWithWaitOption(ctx, m, false)
+}
+
+func (n *node) stepWait(ctx context.Context, m pb.Message) error {
+	return n.stepWithWaitOption(ctx, m, true)
+}
+
+// Step advances the state machine using msgs. The ctx.Err() will be returned,
+// if any.
+func (n *node) stepWithWaitOption(ctx context.Context, m pb.Message, wait bool) error {
+	if m.Type != pb.MsgProp {
+		select {
+		case n.recvc <- m:
+			return nil
+		case <-ctx.Done():
+			return ctx.Err()
+		case <-n.done:
+			return ErrStopped
+		}
+	}
+	ch := n.propc
+	pm := msgWithResult{m: m}
+	if wait {
+		pm.result = make(chan error, 1)
+	}
+	select {
+	case ch <- pm:
+		if !wait {
+			return nil
+		}
+	case <-ctx.Done():
+		return ctx.Err()
+	case <-n.done:
+		return ErrStopped
+	}
+	select {
+	case err := <-pm.result:
+		if err != nil {
+			return err
+		}
+	case <-ctx.Done():
+		return ctx.Err()
+	case <-n.done:
+		return ErrStopped
+	}
+	return nil
+}
+
+func (n *node) Ready() <-chan Ready { return n.readyc }
+
+func (n *node) Advance() {
+	select {
+	case n.advancec <- struct{}{}:
+	case <-n.done:
+	}
+}
+
+func (n *node) ApplyConfChange(cc pb.ConfChangeI) *pb.ConfState {
+	var cs pb.ConfState
+	select {
+	case n.confc <- cc.AsV2():
+	case <-n.done:
+	}
+	select {
+	case cs = <-n.confstatec:
+	case <-n.done:
+	}
+	return &cs
+}
+
+func (n *node) Status() Status {
+	c := make(chan Status)
+	select {
+	case n.status <- c:
+		return <-c
+	case <-n.done:
+		return Status{}
+	}
+}
+
+func (n *node) ReportUnreachable(id uint64) {
+	select {
+	case n.recvc <- pb.Message{Type: pb.MsgUnreachable, From: id}:
+	case <-n.done:
+	}
+}
+
+func (n *node) ReportSnapshot(id uint64, status SnapshotStatus) {
+	rej := status == SnapshotFailure
+
+	select {
+	case n.recvc <- pb.Message{Type: pb.MsgSnapStatus, From: id, Reject: rej}:
+	case <-n.done:
+	}
+}
+
+func (n *node) TransferLeadership(ctx context.Context, lead, transferee uint64) {
+	select {
+	// manually set 'from' and 'to', so that leader can voluntarily transfers its leadership
+	case n.recvc <- pb.Message{Type: pb.MsgTransferLeader, From: transferee, To: lead}:
+	case <-n.done:
+	case <-ctx.Done():
+	}
+}
+
+func (n *node) ForgetLeader(ctx context.Context) error {
+	return n.step(ctx, pb.Message{Type: pb.MsgForgetLeader})
+}
+
+func (n *node) ReadIndex(ctx context.Context, rctx []byte) error {
+	return n.step(ctx, pb.Message{Type: pb.MsgReadIndex, Entries: []pb.Entry{{Data: rctx}}})
+}