diff --git a/vendor/go.etcd.io/etcd/raft/node.go b/vendor/go.etcd.io/etcd/raft/node.go
new file mode 100644
index 0000000..2ec2c3a
--- /dev/null
+++ b/vendor/go.etcd.io/etcd/raft/node.go
@@ -0,0 +1,611 @@
+// 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/etcd/raft/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.
+	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.
+	Entries []pb.Entry
+
+	// Snapshot specifies the snapshot to be saved to stable storage.
+	Snapshot pb.Snapshot
+
+	// CommittedEntries specifies entries to be committed to a
+	// store/state-machine. These have previously been committed to stable
+	// store.
+	CommittedEntries []pb.Entry
+
+	// Messages specifies outbound messages to be sent AFTER Entries are
+	// committed to stable storage.
+	// 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 synchronously
+	// written to disk or if an asynchronous 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
+}
+
+func (rd Ready) containsUpdates() bool {
+	return rd.SoftState != nil || !IsEmptyHardState(rd.HardState) ||
+		!IsEmptySnap(rd.Snapshot) || len(rd.Entries) > 0 ||
+		len(rd.CommittedEntries) > 0 || len(rd.Messages) > 0 || len(rd.ReadStates) != 0
+}
+
+// appliedCursor extracts from the Ready the highest index the client has
+// applied (once the Ready is confirmed via Advance). If no information is
+// contained in the Ready, returns zero.
+func (rd Ready) appliedCursor() uint64 {
+	if n := len(rd.CommittedEntries); n > 0 {
+		return rd.CommittedEntries[n-1].Index
+	}
+	if index := rd.Snapshot.Metadata.Index; index > 0 {
+		return index
+	}
+	return 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 config change.
+	// At most one ConfChange can be in the process of going through consensus.
+	// Application needs to call ApplyConfChange when applying EntryConfChange type entry.
+	ProposeConfChange(ctx context.Context, cc pb.ConfChange) 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.
+	//
+	// 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.
+	Advance()
+	// ApplyConfChange applies config change to the local node.
+	// Returns an opaque ConfState protobuf which must be recorded
+	// in snapshots. Will never return nil; it returns a pointer only
+	// to match MemoryStorage.Compact.
+	ApplyConfChange(cc pb.ConfChange) *pb.ConfState
+
+	// TransferLeadership attempts to transfer leadership to the given transferee.
+	TransferLeadership(ctx context.Context, lead, transferee uint64)
+
+	// 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.
+	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
+}
+
+// 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.
+func StartNode(c *Config, peers []Peer) Node {
+	r := newRaft(c)
+	// become the follower at term 1 and apply initial configuration
+	// entries of term 1
+	r.becomeFollower(1, None)
+	for _, peer := range peers {
+		cc := pb.ConfChange{Type: pb.ConfChangeAddNode, NodeID: peer.ID, Context: peer.Context}
+		d, err := cc.Marshal()
+		if err != nil {
+			panic("unexpected marshal error")
+		}
+		e := pb.Entry{Type: pb.EntryConfChange, Term: 1, Index: r.raftLog.lastIndex() + 1, Data: d}
+		r.raftLog.append(e)
+	}
+	// Mark these initial entries as committed.
+	// TODO(bdarnell): These entries are still unstable; do we need to preserve
+	// the invariant that committed < unstable?
+	r.raftLog.committed = r.raftLog.lastIndex()
+	// Now apply them, mainly so that the application can call Campaign
+	// immediately after StartNode in tests. Note that these nodes will
+	// be added to raft twice: here and when the application's Ready
+	// loop calls ApplyConfChange. The calls to addNode must come after
+	// all calls to raftLog.append so progress.next is set after these
+	// bootstrapping entries (it is an error if we try to append these
+	// entries since they have already been committed).
+	// We do not set raftLog.applied so the application will be able
+	// to observe all conf changes via Ready.CommittedEntries.
+	for _, peer := range peers {
+		r.addNode(peer.ID)
+	}
+
+	n := newNode()
+	n.logger = c.Logger
+	go n.run(r)
+	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 {
+	r := newRaft(c)
+
+	n := newNode()
+	n.logger = c.Logger
+	go n.run(r)
+	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.ConfChange
+	confstatec chan pb.ConfState
+	readyc     chan Ready
+	advancec   chan struct{}
+	tickc      chan struct{}
+	done       chan struct{}
+	stop       chan struct{}
+	status     chan chan Status
+
+	logger Logger
+}
+
+func newNode() node {
+	return node{
+		propc:      make(chan msgWithResult),
+		recvc:      make(chan pb.Message),
+		confc:      make(chan pb.ConfChange),
+		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),
+	}
+}
+
+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(r *raft) {
+	var propc chan msgWithResult
+	var readyc chan Ready
+	var advancec chan struct{}
+	var prevLastUnstablei, prevLastUnstablet uint64
+	var havePrevLastUnstablei bool
+	var prevSnapi uint64
+	var applyingToI uint64
+	var rd Ready
+
+	lead := None
+	prevSoftSt := r.softState()
+	prevHardSt := emptyState
+
+	for {
+		if advancec != nil {
+			readyc = nil
+		} else {
+			rd = newReady(r, prevSoftSt, prevHardSt)
+			if rd.containsUpdates() {
+				readyc = n.readyc
+			} else {
+				readyc = nil
+			}
+		}
+
+		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:
+			// filter out response message from unknown From.
+			if pr := r.getProgress(m.From); pr != nil || !IsResponseMsg(m.Type) {
+				r.Step(m)
+			}
+		case cc := <-n.confc:
+			if cc.NodeID == None {
+				select {
+				case n.confstatec <- pb.ConfState{
+					Nodes:    r.nodes(),
+					Learners: r.learnerNodes()}:
+				case <-n.done:
+				}
+				break
+			}
+			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
+				if cc.NodeID == r.id {
+					propc = nil
+				}
+				r.removeNode(cc.NodeID)
+			case pb.ConfChangeUpdateNode:
+			default:
+				panic("unexpected conf type")
+			}
+			select {
+			case n.confstatec <- pb.ConfState{
+				Nodes:    r.nodes(),
+				Learners: r.learnerNodes()}:
+			case <-n.done:
+			}
+		case <-n.tickc:
+			r.tick()
+		case readyc <- rd:
+			if rd.SoftState != nil {
+				prevSoftSt = rd.SoftState
+			}
+			if len(rd.Entries) > 0 {
+				prevLastUnstablei = rd.Entries[len(rd.Entries)-1].Index
+				prevLastUnstablet = rd.Entries[len(rd.Entries)-1].Term
+				havePrevLastUnstablei = true
+			}
+			if !IsEmptyHardState(rd.HardState) {
+				prevHardSt = rd.HardState
+			}
+			if !IsEmptySnap(rd.Snapshot) {
+				prevSnapi = rd.Snapshot.Metadata.Index
+			}
+			if index := rd.appliedCursor(); index != 0 {
+				applyingToI = index
+			}
+
+			r.msgs = nil
+			r.readStates = nil
+			r.reduceUncommittedSize(rd.CommittedEntries)
+			advancec = n.advancec
+		case <-advancec:
+			if applyingToI != 0 {
+				r.raftLog.appliedTo(applyingToI)
+				applyingToI = 0
+			}
+			if havePrevLastUnstablei {
+				r.raftLog.stableTo(prevLastUnstablei, prevLastUnstablet)
+				havePrevLastUnstablei = false
+			}
+			r.raftLog.stableSnapTo(prevSnapi)
+			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.logger.Warningf("A tick missed to fire. Node blocks too long!")
+	}
+}
+
+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) {
+		// TODO: return an error?
+		return nil
+	}
+	return n.step(ctx, m)
+}
+
+func (n *node) ProposeConfChange(ctx context.Context, cc pb.ConfChange) error {
+	data, err := cc.Marshal()
+	if err != nil {
+		return err
+	}
+	return n.Step(ctx, pb.Message{Type: pb.MsgProp, Entries: []pb.Entry{{Type: pb.EntryConfChange, Data: data}}})
+}
+
+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.ConfChange) *pb.ConfState {
+	var cs pb.ConfState
+	select {
+	case n.confc <- cc:
+	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) ReadIndex(ctx context.Context, rctx []byte) error {
+	return n.step(ctx, pb.Message{Type: pb.MsgReadIndex, Entries: []pb.Entry{{Data: rctx}}})
+}
+
+func newReady(r *raft, prevSoftSt *SoftState, prevHardSt pb.HardState) Ready {
+	rd := Ready{
+		Entries:          r.raftLog.unstableEntries(),
+		CommittedEntries: r.raftLog.nextEnts(),
+		Messages:         r.msgs,
+	}
+	if softSt := r.softState(); !softSt.equal(prevSoftSt) {
+		rd.SoftState = softSt
+	}
+	if hardSt := r.hardState(); !isHardStateEqual(hardSt, prevHardSt) {
+		rd.HardState = hardSt
+	}
+	if r.raftLog.unstable.snapshot != nil {
+		rd.Snapshot = *r.raftLog.unstable.snapshot
+	}
+	if len(r.readStates) != 0 {
+		rd.ReadStates = r.readStates
+	}
+	rd.MustSync = MustSync(r.hardState(), prevHardSt, len(rd.Entries))
+	return rd
+}
+
+// MustSync returns true if the hard state and count of Raft entries indicate
+// that a synchronous write to persistent storage is required.
+func MustSync(st, prevst pb.HardState, entsnum int) bool {
+	// Persistent state on all servers:
+	// (Updated on stable storage before responding to RPCs)
+	// currentTerm
+	// votedFor
+	// log entries[]
+	return entsnum != 0 || st.Vote != prevst.Vote || st.Term != prevst.Term
+}