diff --git a/vendor/go.etcd.io/raft/v3/util.go b/vendor/go.etcd.io/raft/v3/util.go
new file mode 100644
index 0000000..8f78178
--- /dev/null
+++ b/vendor/go.etcd.io/raft/v3/util.go
@@ -0,0 +1,325 @@
+// 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"
+	"fmt"
+	"strings"
+
+	pb "go.etcd.io/raft/v3/raftpb"
+)
+
+func (st StateType) MarshalJSON() ([]byte, error) {
+	return []byte(fmt.Sprintf("%q", st.String())), nil
+}
+
+var isLocalMsg = [...]bool{
+	pb.MsgHup:               true,
+	pb.MsgBeat:              true,
+	pb.MsgUnreachable:       true,
+	pb.MsgSnapStatus:        true,
+	pb.MsgCheckQuorum:       true,
+	pb.MsgStorageAppend:     true,
+	pb.MsgStorageAppendResp: true,
+	pb.MsgStorageApply:      true,
+	pb.MsgStorageApplyResp:  true,
+}
+
+var isResponseMsg = [...]bool{
+	pb.MsgAppResp:           true,
+	pb.MsgVoteResp:          true,
+	pb.MsgHeartbeatResp:     true,
+	pb.MsgUnreachable:       true,
+	pb.MsgReadIndexResp:     true,
+	pb.MsgPreVoteResp:       true,
+	pb.MsgStorageAppendResp: true,
+	pb.MsgStorageApplyResp:  true,
+}
+
+func isMsgInArray(msgt pb.MessageType, arr []bool) bool {
+	i := int(msgt)
+	return i < len(arr) && arr[i]
+}
+
+func IsLocalMsg(msgt pb.MessageType) bool {
+	return isMsgInArray(msgt, isLocalMsg[:])
+}
+
+func IsResponseMsg(msgt pb.MessageType) bool {
+	return isMsgInArray(msgt, isResponseMsg[:])
+}
+
+func IsLocalMsgTarget(id uint64) bool {
+	return id == LocalAppendThread || id == LocalApplyThread
+}
+
+// voteResponseType maps vote and prevote message types to their corresponding responses.
+func voteRespMsgType(msgt pb.MessageType) pb.MessageType {
+	switch msgt {
+	case pb.MsgVote:
+		return pb.MsgVoteResp
+	case pb.MsgPreVote:
+		return pb.MsgPreVoteResp
+	default:
+		panic(fmt.Sprintf("not a vote message: %s", msgt))
+	}
+}
+
+func DescribeHardState(hs pb.HardState) string {
+	var buf strings.Builder
+	fmt.Fprintf(&buf, "Term:%d", hs.Term)
+	if hs.Vote != 0 {
+		fmt.Fprintf(&buf, " Vote:%d", hs.Vote)
+	}
+	fmt.Fprintf(&buf, " Commit:%d", hs.Commit)
+	return buf.String()
+}
+
+func DescribeSoftState(ss SoftState) string {
+	return fmt.Sprintf("Lead:%d State:%s", ss.Lead, ss.RaftState)
+}
+
+func DescribeConfState(state pb.ConfState) string {
+	return fmt.Sprintf(
+		"Voters:%v VotersOutgoing:%v Learners:%v LearnersNext:%v AutoLeave:%v",
+		state.Voters, state.VotersOutgoing, state.Learners, state.LearnersNext, state.AutoLeave,
+	)
+}
+
+func DescribeSnapshot(snap pb.Snapshot) string {
+	m := snap.Metadata
+	return fmt.Sprintf("Index:%d Term:%d ConfState:%s", m.Index, m.Term, DescribeConfState(m.ConfState))
+}
+
+func DescribeReady(rd Ready, f EntryFormatter) string {
+	var buf strings.Builder
+	if rd.SoftState != nil {
+		fmt.Fprint(&buf, DescribeSoftState(*rd.SoftState))
+		buf.WriteByte('\n')
+	}
+	if !IsEmptyHardState(rd.HardState) {
+		fmt.Fprintf(&buf, "HardState %s", DescribeHardState(rd.HardState))
+		buf.WriteByte('\n')
+	}
+	if len(rd.ReadStates) > 0 {
+		fmt.Fprintf(&buf, "ReadStates %v\n", rd.ReadStates)
+	}
+	if len(rd.Entries) > 0 {
+		buf.WriteString("Entries:\n")
+		fmt.Fprint(&buf, DescribeEntries(rd.Entries, f))
+	}
+	if !IsEmptySnap(rd.Snapshot) {
+		fmt.Fprintf(&buf, "Snapshot %s\n", DescribeSnapshot(rd.Snapshot))
+	}
+	if len(rd.CommittedEntries) > 0 {
+		buf.WriteString("CommittedEntries:\n")
+		fmt.Fprint(&buf, DescribeEntries(rd.CommittedEntries, f))
+	}
+	if len(rd.Messages) > 0 {
+		buf.WriteString("Messages:\n")
+		for _, msg := range rd.Messages {
+			fmt.Fprint(&buf, DescribeMessage(msg, f))
+			buf.WriteByte('\n')
+		}
+	}
+	if buf.Len() > 0 {
+		return fmt.Sprintf("Ready MustSync=%t:\n%s", rd.MustSync, buf.String())
+	}
+	return "<empty Ready>"
+}
+
+// EntryFormatter can be implemented by the application to provide human-readable formatting
+// of entry data. Nil is a valid EntryFormatter and will use a default format.
+type EntryFormatter func([]byte) string
+
+// DescribeMessage returns a concise human-readable description of a
+// Message for debugging.
+func DescribeMessage(m pb.Message, f EntryFormatter) string {
+	return describeMessageWithIndent("", m, f)
+}
+
+func describeMessageWithIndent(indent string, m pb.Message, f EntryFormatter) string {
+	var buf bytes.Buffer
+	fmt.Fprintf(&buf, "%s%s->%s %v Term:%d Log:%d/%d", indent,
+		describeTarget(m.From), describeTarget(m.To), m.Type, m.Term, m.LogTerm, m.Index)
+	if m.Reject {
+		fmt.Fprintf(&buf, " Rejected (Hint: %d)", m.RejectHint)
+	}
+	if m.Commit != 0 {
+		fmt.Fprintf(&buf, " Commit:%d", m.Commit)
+	}
+	if m.Vote != 0 {
+		fmt.Fprintf(&buf, " Vote:%d", m.Vote)
+	}
+	if ln := len(m.Entries); ln == 1 {
+		fmt.Fprintf(&buf, " Entries:[%s]", DescribeEntry(m.Entries[0], f))
+	} else if ln > 1 {
+		fmt.Fprint(&buf, " Entries:[")
+		for _, e := range m.Entries {
+			fmt.Fprintf(&buf, "\n%s  ", indent)
+			buf.WriteString(DescribeEntry(e, f))
+		}
+		fmt.Fprintf(&buf, "\n%s]", indent)
+	}
+	if s := m.Snapshot; s != nil && !IsEmptySnap(*s) {
+		fmt.Fprintf(&buf, "\n%s  Snapshot: %s", indent, DescribeSnapshot(*s))
+	}
+	if len(m.Responses) > 0 {
+		fmt.Fprintf(&buf, " Responses:[")
+		for _, m := range m.Responses {
+			buf.WriteString("\n")
+			buf.WriteString(describeMessageWithIndent(indent+"  ", m, f))
+		}
+		fmt.Fprintf(&buf, "\n%s]", indent)
+	}
+	return buf.String()
+}
+
+func describeTarget(id uint64) string {
+	switch id {
+	case None:
+		return "None"
+	case LocalAppendThread:
+		return "AppendThread"
+	case LocalApplyThread:
+		return "ApplyThread"
+	default:
+		return fmt.Sprintf("%x", id)
+	}
+}
+
+// DescribeEntry returns a concise human-readable description of an
+// Entry for debugging.
+func DescribeEntry(e pb.Entry, f EntryFormatter) string {
+	if f == nil {
+		f = func(data []byte) string { return fmt.Sprintf("%q", data) }
+	}
+
+	formatConfChange := func(cc pb.ConfChangeI) string {
+		// TODO(tbg): give the EntryFormatter a type argument so that it gets
+		// a chance to expose the Context.
+		return pb.ConfChangesToString(cc.AsV2().Changes)
+	}
+
+	var formatted string
+	switch e.Type {
+	case pb.EntryNormal:
+		formatted = f(e.Data)
+	case pb.EntryConfChange:
+		var cc pb.ConfChange
+		if err := cc.Unmarshal(e.Data); err != nil {
+			formatted = err.Error()
+		} else {
+			formatted = formatConfChange(cc)
+		}
+	case pb.EntryConfChangeV2:
+		var cc pb.ConfChangeV2
+		if err := cc.Unmarshal(e.Data); err != nil {
+			formatted = err.Error()
+		} else {
+			formatted = formatConfChange(cc)
+		}
+	}
+	if formatted != "" {
+		formatted = " " + formatted
+	}
+	return fmt.Sprintf("%d/%d %s%s", e.Term, e.Index, e.Type, formatted)
+}
+
+// DescribeEntries calls DescribeEntry for each Entry, adding a newline to
+// each.
+func DescribeEntries(ents []pb.Entry, f EntryFormatter) string {
+	var buf bytes.Buffer
+	for _, e := range ents {
+		_, _ = buf.WriteString(DescribeEntry(e, f) + "\n")
+	}
+	return buf.String()
+}
+
+// entryEncodingSize represents the protocol buffer encoding size of one or more
+// entries.
+type entryEncodingSize uint64
+
+func entsSize(ents []pb.Entry) entryEncodingSize {
+	var size entryEncodingSize
+	for _, ent := range ents {
+		size += entryEncodingSize(ent.Size())
+	}
+	return size
+}
+
+// limitSize returns the longest prefix of the given entries slice, such that
+// its total byte size does not exceed maxSize. Always returns a non-empty slice
+// if the input is non-empty, so, as an exception, if the size of the first
+// entry exceeds maxSize, a non-empty slice with just this entry is returned.
+func limitSize(ents []pb.Entry, maxSize entryEncodingSize) []pb.Entry {
+	if len(ents) == 0 {
+		return ents
+	}
+	size := ents[0].Size()
+	for limit := 1; limit < len(ents); limit++ {
+		size += ents[limit].Size()
+		if entryEncodingSize(size) > maxSize {
+			return ents[:limit]
+		}
+	}
+	return ents
+}
+
+// entryPayloadSize represents the size of one or more entries' payloads.
+// Notably, it does not depend on its Index or Term. Entries with empty
+// payloads, like those proposed after a leadership change, are considered
+// to be zero size.
+type entryPayloadSize uint64
+
+// payloadSize is the size of the payload of the provided entry.
+func payloadSize(e pb.Entry) entryPayloadSize {
+	return entryPayloadSize(len(e.Data))
+}
+
+// payloadsSize is the size of the payloads of the provided entries.
+func payloadsSize(ents []pb.Entry) entryPayloadSize {
+	var s entryPayloadSize
+	for _, e := range ents {
+		s += payloadSize(e)
+	}
+	return s
+}
+
+func assertConfStatesEquivalent(l Logger, cs1, cs2 pb.ConfState) {
+	err := cs1.Equivalent(cs2)
+	if err == nil {
+		return
+	}
+	l.Panic(err)
+}
+
+// extend appends vals to the given dst slice. It differs from the standard
+// slice append only in the way it allocates memory. If cap(dst) is not enough
+// for appending the values, precisely size len(dst)+len(vals) is allocated.
+//
+// Use this instead of standard append in situations when this is the last
+// append to dst, so there is no sense in allocating more than needed.
+func extend(dst, vals []pb.Entry) []pb.Entry {
+	need := len(dst) + len(vals)
+	if need <= cap(dst) {
+		return append(dst, vals...) // does not allocate
+	}
+	buf := make([]pb.Entry, need, need) // allocates precisely what's needed
+	copy(buf, dst)
+	copy(buf[len(dst):], vals)
+	return buf
+}