etcdserver: fix data race in cluster

The data race happens when etcd updates member attributes and fetches
member info in http handler at the same time.

etcdserver/cluster.go

@@ -121,7 +121,7 @@ func (c *Cluster) Members() []*Member {
 	defer c.Unlock()
 	var sms SortableMemberSlice
 	for _, m := range c.members {
-		sms = append(sms, m)
+		sms = append(sms, m.Clone())
 	}
 	sort.Sort(sms)
 	return []*Member(sms)
@@ -136,7 +136,7 @@ func (s SortableMemberSlice) Swap(i, j int)      { s[i], s[j] = s[j], s[i] }
 func (c *Cluster) Member(id types.ID) *Member {
 	c.Lock()
 	defer c.Unlock()
-	return c.members[id]
+	return c.members[id].Clone()
 }
 
 // MemberByName returns a Member with the given name if exists.
@@ -153,7 +153,7 @@ func (c *Cluster) MemberByName(name string) *Member {
 			memb = m
 		}
 	}
-	return memb
+	return memb.Clone()
 }
 
 func (c *Cluster) MemberIDs() []types.ID {
@@ -335,6 +335,12 @@ func (c *Cluster) RemoveMember(id types.ID) {
 	c.removed[id] = true
 }
 
+func (c *Cluster) UpdateMemberAttributes(id types.ID, attr Attributes) {
+	c.Lock()
+	defer c.Unlock()
+	c.members[id].Attributes = attr
+}
+
 // nodeToMember builds member through a store node.
 // the child nodes of the given node should be sorted by key.
 func nodeToMember(n *store.NodeExtern) (*Member, error) {

etcdserver/member.go

@@ -80,6 +80,27 @@ func (m *Member) PickPeerURL() string {
 	return m.PeerURLs[rand.Intn(len(m.PeerURLs))]
 }
 
+func (m *Member) Clone() *Member {
+	if m == nil {
+		return nil
+	}
+	mm := &Member{
+		ID: m.ID,
+		Attributes: Attributes{
+			Name: m.Name,
+		},
+	}
+	if m.PeerURLs != nil {
+		mm.PeerURLs = make([]string, len(m.PeerURLs))
+		copy(mm.PeerURLs, m.PeerURLs)
+	}
+	if m.ClientURLs != nil {
+		mm.ClientURLs = make([]string, len(m.ClientURLs))
+		copy(mm.ClientURLs, m.ClientURLs)
+	}
+	return mm
+}
+
 func memberStoreKey(id types.ID) string {
 	return path.Join(storeMembersPrefix, id.String())
 }

etcdserver/member_test.go

@@ -18,6 +18,7 @@ package etcdserver
 
 import (
 	"net/url"
+	"reflect"
 	"testing"
 	"time"
 
@@ -88,3 +89,21 @@ func TestMemberPick(t *testing.T) {
 		}
 	}
 }
+
+func TestMemberClone(t *testing.T) {
+	tests := []*Member{
+		newTestMemberp(1, nil, "abc", nil),
+		newTestMemberp(1, []string{"http://a"}, "abc", nil),
+		newTestMemberp(1, nil, "abc", []string{"http://b"}),
+		newTestMemberp(1, []string{"http://a"}, "abc", []string{"http://b"}),
+	}
+	for i, tt := range tests {
+		nm := tt.Clone()
+		if nm == tt {
+			t.Errorf("#%d: the pointers are the same, and clone doesn't happen", i)
+		}
+		if !reflect.DeepEqual(nm, tt) {
+			t.Errorf("#%d: member = %+v, want %+v", i, nm, tt)
+		}
+	}
+}

etcdserver/server.go

@@ -618,13 +618,11 @@ func (s *EtcdServer) applyRequest(r pb.Request) Response {
 		default:
 			if storeMemberAttributeRegexp.MatchString(r.Path) {
 				id := mustParseMemberIDFromKey(path.Dir(r.Path))
-				m := s.Cluster.Member(id)
-				if m == nil {
-					log.Panicf("fetch member %s should never fail", id)
-				}
-				if err := json.Unmarshal([]byte(r.Val), &m.Attributes); err != nil {
+				var attr Attributes
+				if err := json.Unmarshal([]byte(r.Val), &attr); err != nil {
 					log.Panicf("unmarshal %s should never fail: %v", r.Val, err)
 				}
+				s.Cluster.UpdateMemberAttributes(id, attr)
 			}
 			return f(s.store.Set(r.Path, r.Dir, r.Val, expr))
 		}