diff --git a/vendor/go.etcd.io/etcd/pkg/types/set.go b/vendor/go.etcd.io/etcd/pkg/types/set.go
new file mode 100644
index 0000000..e7a3cdc
--- /dev/null
+++ b/vendor/go.etcd.io/etcd/pkg/types/set.go
@@ -0,0 +1,195 @@
+// 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 types
+
+import (
+	"reflect"
+	"sort"
+	"sync"
+)
+
+type Set interface {
+	Add(string)
+	Remove(string)
+	Contains(string) bool
+	Equals(Set) bool
+	Length() int
+	Values() []string
+	Copy() Set
+	Sub(Set) Set
+}
+
+func NewUnsafeSet(values ...string) *unsafeSet {
+	set := &unsafeSet{make(map[string]struct{})}
+	for _, v := range values {
+		set.Add(v)
+	}
+	return set
+}
+
+func NewThreadsafeSet(values ...string) *tsafeSet {
+	us := NewUnsafeSet(values...)
+	return &tsafeSet{us, sync.RWMutex{}}
+}
+
+type unsafeSet struct {
+	d map[string]struct{}
+}
+
+// Add adds a new value to the set (no-op if the value is already present)
+func (us *unsafeSet) Add(value string) {
+	us.d[value] = struct{}{}
+}
+
+// Remove removes the given value from the set
+func (us *unsafeSet) Remove(value string) {
+	delete(us.d, value)
+}
+
+// Contains returns whether the set contains the given value
+func (us *unsafeSet) Contains(value string) (exists bool) {
+	_, exists = us.d[value]
+	return exists
+}
+
+// ContainsAll returns whether the set contains all given values
+func (us *unsafeSet) ContainsAll(values []string) bool {
+	for _, s := range values {
+		if !us.Contains(s) {
+			return false
+		}
+	}
+	return true
+}
+
+// Equals returns whether the contents of two sets are identical
+func (us *unsafeSet) Equals(other Set) bool {
+	v1 := sort.StringSlice(us.Values())
+	v2 := sort.StringSlice(other.Values())
+	v1.Sort()
+	v2.Sort()
+	return reflect.DeepEqual(v1, v2)
+}
+
+// Length returns the number of elements in the set
+func (us *unsafeSet) Length() int {
+	return len(us.d)
+}
+
+// Values returns the values of the Set in an unspecified order.
+func (us *unsafeSet) Values() (values []string) {
+	values = make([]string, 0)
+	for val := range us.d {
+		values = append(values, val)
+	}
+	return values
+}
+
+// Copy creates a new Set containing the values of the first
+func (us *unsafeSet) Copy() Set {
+	cp := NewUnsafeSet()
+	for val := range us.d {
+		cp.Add(val)
+	}
+
+	return cp
+}
+
+// Sub removes all elements in other from the set
+func (us *unsafeSet) Sub(other Set) Set {
+	oValues := other.Values()
+	result := us.Copy().(*unsafeSet)
+
+	for _, val := range oValues {
+		if _, ok := result.d[val]; !ok {
+			continue
+		}
+		delete(result.d, val)
+	}
+
+	return result
+}
+
+type tsafeSet struct {
+	us *unsafeSet
+	m  sync.RWMutex
+}
+
+func (ts *tsafeSet) Add(value string) {
+	ts.m.Lock()
+	defer ts.m.Unlock()
+	ts.us.Add(value)
+}
+
+func (ts *tsafeSet) Remove(value string) {
+	ts.m.Lock()
+	defer ts.m.Unlock()
+	ts.us.Remove(value)
+}
+
+func (ts *tsafeSet) Contains(value string) (exists bool) {
+	ts.m.RLock()
+	defer ts.m.RUnlock()
+	return ts.us.Contains(value)
+}
+
+func (ts *tsafeSet) Equals(other Set) bool {
+	ts.m.RLock()
+	defer ts.m.RUnlock()
+
+	// If ts and other represent the same variable, avoid calling
+	// ts.us.Equals(other), to avoid double RLock bug
+	if _other, ok := other.(*tsafeSet); ok {
+		if _other == ts {
+			return true
+		}
+	}
+	return ts.us.Equals(other)
+}
+
+func (ts *tsafeSet) Length() int {
+	ts.m.RLock()
+	defer ts.m.RUnlock()
+	return ts.us.Length()
+}
+
+func (ts *tsafeSet) Values() (values []string) {
+	ts.m.RLock()
+	defer ts.m.RUnlock()
+	return ts.us.Values()
+}
+
+func (ts *tsafeSet) Copy() Set {
+	ts.m.RLock()
+	defer ts.m.RUnlock()
+	usResult := ts.us.Copy().(*unsafeSet)
+	return &tsafeSet{usResult, sync.RWMutex{}}
+}
+
+func (ts *tsafeSet) Sub(other Set) Set {
+	ts.m.RLock()
+	defer ts.m.RUnlock()
+
+	// If ts and other represent the same variable, avoid calling
+	// ts.us.Sub(other), to avoid double RLock bug
+	if _other, ok := other.(*tsafeSet); ok {
+		if _other == ts {
+			usResult := NewUnsafeSet()
+			return &tsafeSet{usResult, sync.RWMutex{}}
+		}
+	}
+	usResult := ts.us.Sub(other).(*unsafeSet)
+	return &tsafeSet{usResult, sync.RWMutex{}}
+}