diff --git a/vendor/go.etcd.io/etcd/raft/quorum/majority.go b/vendor/go.etcd.io/etcd/raft/quorum/majority.go
new file mode 100644
index 0000000..8858a36
--- /dev/null
+++ b/vendor/go.etcd.io/etcd/raft/quorum/majority.go
@@ -0,0 +1,210 @@
+// Copyright 2019 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 quorum
+
+import (
+	"fmt"
+	"math"
+	"sort"
+	"strings"
+)
+
+// MajorityConfig is a set of IDs that uses majority quorums to make decisions.
+type MajorityConfig map[uint64]struct{}
+
+func (c MajorityConfig) String() string {
+	sl := make([]uint64, 0, len(c))
+	for id := range c {
+		sl = append(sl, id)
+	}
+	sort.Slice(sl, func(i, j int) bool { return sl[i] < sl[j] })
+	var buf strings.Builder
+	buf.WriteByte('(')
+	for i := range sl {
+		if i > 0 {
+			buf.WriteByte(' ')
+		}
+		fmt.Fprint(&buf, sl[i])
+	}
+	buf.WriteByte(')')
+	return buf.String()
+}
+
+// Describe returns a (multi-line) representation of the commit indexes for the
+// given lookuper.
+func (c MajorityConfig) Describe(l AckedIndexer) string {
+	if len(c) == 0 {
+		return "<empty majority quorum>"
+	}
+	type tup struct {
+		id  uint64
+		idx Index
+		ok  bool // idx found?
+		bar int  // length of bar displayed for this tup
+	}
+
+	// Below, populate .bar so that the i-th largest commit index has bar i (we
+	// plot this as sort of a progress bar). The actual code is a bit more
+	// complicated and also makes sure that equal index => equal bar.
+
+	n := len(c)
+	info := make([]tup, 0, n)
+	for id := range c {
+		idx, ok := l.AckedIndex(id)
+		info = append(info, tup{id: id, idx: idx, ok: ok})
+	}
+
+	// Sort by index
+	sort.Slice(info, func(i, j int) bool {
+		if info[i].idx == info[j].idx {
+			return info[i].id < info[j].id
+		}
+		return info[i].idx < info[j].idx
+	})
+
+	// Populate .bar.
+	for i := range info {
+		if i > 0 && info[i-1].idx < info[i].idx {
+			info[i].bar = i
+		}
+	}
+
+	// Sort by ID.
+	sort.Slice(info, func(i, j int) bool {
+		return info[i].id < info[j].id
+	})
+
+	var buf strings.Builder
+
+	// Print.
+	fmt.Fprint(&buf, strings.Repeat(" ", n)+"    idx\n")
+	for i := range info {
+		bar := info[i].bar
+		if !info[i].ok {
+			fmt.Fprint(&buf, "?"+strings.Repeat(" ", n))
+		} else {
+			fmt.Fprint(&buf, strings.Repeat("x", bar)+">"+strings.Repeat(" ", n-bar))
+		}
+		fmt.Fprintf(&buf, " %5d    (id=%d)\n", info[i].idx, info[i].id)
+	}
+	return buf.String()
+}
+
+// Slice returns the MajorityConfig as a sorted slice.
+func (c MajorityConfig) Slice() []uint64 {
+	var sl []uint64
+	for id := range c {
+		sl = append(sl, id)
+	}
+	sort.Slice(sl, func(i, j int) bool { return sl[i] < sl[j] })
+	return sl
+}
+
+func insertionSort(sl []uint64) {
+	a, b := 0, len(sl)
+	for i := a + 1; i < b; i++ {
+		for j := i; j > a && sl[j] < sl[j-1]; j-- {
+			sl[j], sl[j-1] = sl[j-1], sl[j]
+		}
+	}
+}
+
+// CommittedIndex computes the committed index from those supplied via the
+// provided AckedIndexer (for the active config).
+func (c MajorityConfig) CommittedIndex(l AckedIndexer) Index {
+	n := len(c)
+	if n == 0 {
+		// This plays well with joint quorums which, when one half is the zero
+		// MajorityConfig, should behave like the other half.
+		return math.MaxUint64
+	}
+
+	// Use an on-stack slice to collect the committed indexes when n <= 7
+	// (otherwise we alloc). The alternative is to stash a slice on
+	// MajorityConfig, but this impairs usability (as is, MajorityConfig is just
+	// a map, and that's nice). The assumption is that running with a
+	// replication factor of >7 is rare, and in cases in which it happens
+	// performance is a lesser concern (additionally the performance
+	// implications of an allocation here are far from drastic).
+	var stk [7]uint64
+	var srt []uint64
+	if len(stk) >= n {
+		srt = stk[:n]
+	} else {
+		srt = make([]uint64, n)
+	}
+
+	{
+		// Fill the slice with the indexes observed. Any unused slots will be
+		// left as zero; these correspond to voters that may report in, but
+		// haven't yet. We fill from the right (since the zeroes will end up on
+		// the left after sorting below anyway).
+		i := n - 1
+		for id := range c {
+			if idx, ok := l.AckedIndex(id); ok {
+				srt[i] = uint64(idx)
+				i--
+			}
+		}
+	}
+
+	// Sort by index. Use a bespoke algorithm (copied from the stdlib's sort
+	// package) to keep srt on the stack.
+	insertionSort(srt)
+
+	// The smallest index into the array for which the value is acked by a
+	// quorum. In other words, from the end of the slice, move n/2+1 to the
+	// left (accounting for zero-indexing).
+	pos := n - (n/2 + 1)
+	return Index(srt[pos])
+}
+
+// VoteResult takes a mapping of voters to yes/no (true/false) votes and returns
+// a result indicating whether the vote is pending (i.e. neither a quorum of
+// yes/no has been reached), won (a quorum of yes has been reached), or lost (a
+// quorum of no has been reached).
+func (c MajorityConfig) VoteResult(votes map[uint64]bool) VoteResult {
+	if len(c) == 0 {
+		// By convention, the elections on an empty config win. This comes in
+		// handy with joint quorums because it'll make a half-populated joint
+		// quorum behave like a majority quorum.
+		return VoteWon
+	}
+
+	ny := [2]int{} // vote counts for no and yes, respectively
+
+	var missing int
+	for id := range c {
+		v, ok := votes[id]
+		if !ok {
+			missing++
+			continue
+		}
+		if v {
+			ny[1]++
+		} else {
+			ny[0]++
+		}
+	}
+
+	q := len(c)/2 + 1
+	if ny[1] >= q {
+		return VoteWon
+	}
+	if ny[1]+missing >= q {
+		return VotePending
+	}
+	return VoteLost
+}