Refactor to create a function to return membership in v2 format

Signed-off-by: Geeta Gharpure <geetagh@amazon.com>

etcdutl/snapshot/v3_snapshot.go

@@ -38,7 +38,6 @@ import (
 	"go.etcd.io/etcd/server/v3/etcdserver"
 	"go.etcd.io/etcd/server/v3/etcdserver/api/membership"
 	"go.etcd.io/etcd/server/v3/etcdserver/api/snap"
-	"go.etcd.io/etcd/server/v3/etcdserver/api/v2store"
 	"go.etcd.io/etcd/server/v3/etcdserver/cindex"
 	"go.etcd.io/etcd/server/v3/storage/backend"
 	"go.etcd.io/etcd/server/v3/storage/schema"
@@ -455,17 +454,11 @@ func (s *v3Manager) saveWALAndSnap() (*raftpb.HardState, error) {
 		return nil, err
 	}
 
-	st := v2store.New(etcdserver.StoreClusterPrefix, etcdserver.StoreKeysPrefix)
-	s.cl.Store(st)
-	b, berr := st.SaveNoCopy()
-	if berr != nil {
-		return nil, berr
-	}
 	confState := raftpb.ConfState{
 		Voters: nodeIDs,
 	}
 	raftSnap := raftpb.Snapshot{
-		Data: b,
+		Data: etcdserver.GetMembershipInfoInV2Format(s.lg, s.cl),
 		Metadata: raftpb.SnapshotMetadata{
 			Index:     commit,
 			Term:      term,

server/etcdserver/cluster_util.go

@@ -28,6 +28,7 @@ import (
 	"go.etcd.io/etcd/api/v3/version"
 	"go.etcd.io/etcd/client/pkg/v3/types"
 	"go.etcd.io/etcd/server/v3/etcdserver/api/membership"
+	"go.etcd.io/etcd/server/v3/etcdserver/api/v2store"
 	"go.etcd.io/etcd/server/v3/etcdserver/errors"
 
 	"github.com/coreos/go-semver/semver"
@@ -416,3 +417,14 @@ func convertToClusterVersion(v string) (*semver.Version, error) {
 	ver = &semver.Version{Major: ver.Major, Minor: ver.Minor}
 	return ver, nil
 }
+
+func GetMembershipInfoInV2Format(lg *zap.Logger, cl *membership.RaftCluster) []byte {
+	var st v2store.Store
+	st = v2store.New(StoreClusterPrefix, StoreKeysPrefix)
+	cl.Store(st)
+	d, err := st.SaveNoCopy()
+	if err != nil {
+		lg.Panic("failed to save v2 store", zap.Error(err))
+	}
+	return d
+}

server/etcdserver/server.go

@@ -2076,16 +2076,7 @@ func (s *EtcdServer) snapshot(snapi uint64, confState raftpb.ConfState) {
 
 	s.GoAttach(func() {
 		lg := s.Logger()
-		var st v2store.Store
-		st = v2store.New(StoreClusterPrefix, StoreKeysPrefix)
-		s.cluster.Store(st)
-		d, err := st.SaveNoCopy()
-		// TODO: current store will never fail to do a snapshot
-		// what should we do if the store might fail?
-		if err != nil {
-			lg.Panic("failed to save v2 store", zap.Error(err))
-		}
-		snap, err := s.r.raftStorage.CreateSnapshot(snapi, &confState, d)
+		snap, err := s.r.raftStorage.CreateSnapshot(snapi, &confState, GetMembershipInfoInV2Format(lg, s.cluster))
 		if err != nil {
 			// the snapshot was done asynchronously with the progress of raft.
 			// raft might have already got a newer snapshot.