v2 etcdctl backup: producing consistent state of membership

etcdctl/ctlv2/command/backup_command.go

@@ -15,7 +15,6 @@
 package command
 
 import (
-	"encoding/binary"
 	"log"
 	"os"
 	"path"
@@ -27,9 +26,13 @@ import (
 	"go.etcd.io/etcd/pkg/v3/fileutil"
 	"go.etcd.io/etcd/pkg/v3/idutil"
 	"go.etcd.io/etcd/pkg/v3/pbutil"
+	"go.etcd.io/etcd/pkg/v3/types"
 	"go.etcd.io/etcd/raft/v3/raftpb"
 	"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/mvcc/backend"
 	"go.etcd.io/etcd/server/v3/wal"
 	"go.etcd.io/etcd/server/v3/wal/walpb"
 
@@ -54,11 +57,41 @@ func NewBackupCommand() cli.Command {
 	}
 }
 
+type desiredCluster struct {
+	clusterId types.ID
+	nodeId    types.ID
+	members   []*membership.Member
+	confState raftpb.ConfState
+}
+
+func newDesiredCluster() desiredCluster {
+	idgen := idutil.NewGenerator(0, time.Now())
+	nodeID := idgen.Next()
+	clusterID := idgen.Next()
+
+	return desiredCluster{
+		clusterId: types.ID(clusterID),
+		nodeId:    types.ID(nodeID),
+		members: []*membership.Member{
+			{
+				ID: types.ID(nodeID),
+				Attributes: membership.Attributes{
+					Name: "etcdctl-v2-backup",
+				},
+				RaftAttributes: membership.RaftAttributes{
+					PeerURLs: []string{"http://use-flag--force-new-cluster:2080"},
+				}}},
+		confState: raftpb.ConfState{Voters: []uint64{nodeID}},
+	}
+}
+
 // handleBackup handles a request that intends to do a backup.
 func handleBackup(c *cli.Context) error {
 	var srcWAL string
 	var destWAL string
 
+	lg := zap.NewExample()
+
 	withV3 := c.Bool("with-v3")
 	srcSnap := filepath.Join(c.String("data-dir"), "member", "snap")
 	destSnap := filepath.Join(c.String("backup-dir"), "member", "snap")
@@ -79,13 +112,12 @@ func handleBackup(c *cli.Context) error {
 		log.Fatalf("failed creating backup snapshot dir %v: %v", destSnap, err)
 	}
 
-	walsnap := saveSnap(destSnap, srcSnap)
-	metadata, state, ents := loadWAL(srcWAL, walsnap, withV3)
-	saveDB(filepath.Join(destSnap, "db"), filepath.Join(srcSnap, "db"), state.Commit, withV3)
+	desired := newDesiredCluster()
 
-	idgen := idutil.NewGenerator(0, time.Now())
-	metadata.NodeID = idgen.Next()
-	metadata.ClusterID = idgen.Next()
+	walsnap := saveSnap(lg, destSnap, srcSnap, &desired)
+	metadata, state, ents := loadWAL(srcWAL, walsnap, withV3)
+	destDbPath := filepath.Join(destSnap, "db")
+	saveDB(lg, destDbPath, filepath.Join(srcSnap, "db"), state.Commit, &desired, withV3)
 
 	neww, err := wal.Create(zap.NewExample(), destWAL, pbutil.MustMarshal(&metadata))
 	if err != nil {
@@ -102,22 +134,44 @@ func handleBackup(c *cli.Context) error {
 	return nil
 }
 
-func saveSnap(destSnap, srcSnap string) (walsnap walpb.Snapshot) {
-	ss := snap.New(zap.NewExample(), srcSnap)
+func saveSnap(lg *zap.Logger, destSnap, srcSnap string, desired *desiredCluster) (walsnap walpb.Snapshot) {
+	ss := snap.New(lg, srcSnap)
 	snapshot, err := ss.Load()
 	if err != nil && err != snap.ErrNoSnapshot {
 		log.Fatal(err)
 	}
 	if snapshot != nil {
-		walsnap.Index, walsnap.Term, walsnap.ConfState = snapshot.Metadata.Index, snapshot.Metadata.Term, &snapshot.Metadata.ConfState
-		newss := snap.New(zap.NewExample(), destSnap)
+		walsnap.Index, walsnap.Term, walsnap.ConfState = snapshot.Metadata.Index, snapshot.Metadata.Term, &desired.confState
+		newss := snap.New(lg, destSnap)
+		snapshot.Metadata.ConfState = desired.confState
+		snapshot.Data = mustTranslateV2store(lg, snapshot.Data, desired)
 		if err = newss.SaveSnap(*snapshot); err != nil {
 			log.Fatal(err)
 		}
 	}
 	return walsnap
 }
 
+// mustTranslateV2store processes storeData such that they match 'desiredCluster'.
+// In particular the method overrides membership information.
+func mustTranslateV2store(lg *zap.Logger, storeData []byte, desired *desiredCluster) []byte {
+	st := v2store.New()
+	if err := st.Recovery(storeData); err != nil {
+		lg.Panic("cannot translate v2store", zap.Error(err))
+	}
+
+	raftCluster := membership.NewClusterFromMembers(lg, desired.clusterId, desired.members)
+	raftCluster.SetID(desired.nodeId, desired.clusterId)
+	raftCluster.SetStore(st)
+	raftCluster.PushMembershipToStorage()
+
+	outputData, err := st.Save()
+	if err != nil {
+		lg.Panic("cannot save v2store", zap.Error(err))
+	}
+	return outputData
+}
+
 func loadWAL(srcWAL string, walsnap walpb.Snapshot, v3 bool) (etcdserverpb.Metadata, raftpb.HardState, []raftpb.Entry) {
 	w, err := wal.OpenForRead(zap.NewExample(), srcWAL, walsnap)
 	if err != nil {
@@ -184,7 +238,8 @@ func loadWAL(srcWAL string, walsnap walpb.Snapshot, v3 bool) (etcdserverpb.Metad
 }
 
 // saveDB copies the v3 backend and strips cluster information.
-func saveDB(destDB, srcDB string, idx uint64, v3 bool) {
+func saveDB(lg *zap.Logger, destDB, srcDB string, idx uint64, desired *desiredCluster, v3 bool) {
+
 	// open src db to safely copy db state
 	if v3 {
 		var src *bolt.DB
@@ -223,37 +278,26 @@ func saveDB(destDB, srcDB string, idx uint64, v3 bool) {
 		}
 	}
 
-	db, err := bolt.Open(destDB, 0644, &bolt.Options{})
-	if err != nil {
-		log.Fatal(err)
-	}
-	tx, err := db.Begin(true)
-	if err != nil {
+	be := backend.NewDefaultBackend(destDB)
+	defer be.Close()
+
+	if err := membership.TrimClusterFromBackend(be); err != nil {
 		log.Fatal(err)
 	}
 
-	// remove membership information; should be clobbered by --force-new-cluster
-	// TODO: Consider refactoring to use backend.Backend instead of bolt
-	// and membership.TrimMembershipFromBackend.
-	for _, bucket := range []string{"members", "members_removed", "cluster"} {
-		tx.DeleteBucket([]byte(bucket))
-	}
+	raftCluster := membership.NewClusterFromMembers(lg, desired.clusterId, desired.members)
+	raftCluster.SetID(desired.nodeId, desired.clusterId)
+	raftCluster.SetBackend(be)
+	raftCluster.PushMembershipToStorage()
 
-	// update consistent index to match hard state
 	if !v3 {
-		idxBytes := make([]byte, 8)
-		binary.BigEndian.PutUint64(idxBytes, idx)
-		b, err := tx.CreateBucketIfNotExists([]byte("meta"))
-		if err != nil {
-			log.Fatal(err)
-		}
-		b.Put([]byte("consistent_index"), idxBytes)
+		tx := be.BatchTx()
+		tx.Lock()
+		defer tx.Unlock()
+		tx.UnsafeCreateBucket([]byte("meta"))
+		ci := cindex.NewConsistentIndex(tx)
+		ci.SetConsistentIndex(idx)
+		ci.UnsafeSave(tx)
 	}
 
-	if err := tx.Commit(); err != nil {
-		log.Fatal(err)
-	}
-	if err := db.Close(); err != nil {
-		log.Fatal(err)
-	}
 }

etcdctl/snapshot/v3_snapshot.go

@@ -294,7 +294,7 @@ func (s *v3Manager) saveDB() error {
 }
 
 func (s *v3Manager) copyAndVerifyDB() error {
-	srcf, ferr := os.OpenFile(s.srcDbPath, os.O_RDONLY, 0600)
+	srcf, ferr := os.Open(s.srcDbPath)
 	if ferr != nil {
 		return ferr
 	}

server/etcdserver/api/membership/cluster.go

@@ -854,3 +854,20 @@ func (c *RaftCluster) VotingMemberIDs() []types.ID {
 	sort.Sort(types.IDSlice(ids))
 	return ids
 }
+
+// PushMembershipToStorage is overriding storage information about cluster's
+// members, such that they fully reflect internal RaftCluster's storage.
+func (c *RaftCluster) PushMembershipToStorage() {
+	if c.be != nil {
+		TrimMembershipFromBackend(c.lg, c.be)
+		for _, m := range c.members {
+			mustSaveMemberToBackend(c.lg, c.be, m)
+		}
+	}
+	if c.v2store != nil {
+		TrimMembershipFromV2Store(c.lg, c.v2store)
+		for _, m := range c.members {
+			mustSaveMemberToStore(c.lg, c.v2store, m)
+		}
+	}
+}

server/etcdserver/api/membership/member.go

@@ -20,6 +20,7 @@ import (
 	"fmt"
 	"math/rand"
 	"sort"
+	"strings"
 	"time"
 
 	"go.etcd.io/etcd/pkg/v3/types"
@@ -61,12 +62,10 @@ func NewMemberAsLearner(name string, peerURLs types.URLs, clusterName string, no
 }
 
 func computeMemberId(peerURLs types.URLs, clusterName string, now *time.Time) types.ID {
-	var b []byte
 	peerURLstrs := peerURLs.StringSlice()
 	sort.Strings(peerURLstrs)
-	for _, p := range peerURLstrs {
-		b = append(b, []byte(p)...)
-	}
+	joinedPeerUrls := strings.Join(peerURLstrs, "")
+	b := []byte(joinedPeerUrls)
 
 	b = append(b, []byte(clusterName)...)
 	if now != nil {

server/etcdserver/api/membership/store.go

@@ -57,6 +57,8 @@ func mustSaveMemberToBackend(lg *zap.Logger, be backend.Backend, m *Member) {
 	tx.UnsafePut(membersBucketName, mkey, mvalue)
 }
 
+// TrimClusterFromBackend removes all information about cluster (versions)
+// from the v3 backend.
 func TrimClusterFromBackend(be backend.Backend) error {
 	tx := be.BatchTx()
 	tx.Lock()
@@ -83,7 +85,7 @@ func readMembersFromBackend(lg *zap.Logger, be backend.Backend) (map[types.ID]*M
 	tx.RLock()
 	defer tx.RUnlock()
 	err := tx.UnsafeForEach(membersBucketName, func(k, v []byte) error {
-		memberId := MustParseMemberIDFromBytes(lg, k)
+		memberId := mustParseMemberIDFromBytes(lg, k)
 		m := &Member{ID: memberId}
 		if err := json.Unmarshal(v, &m); err != nil {
 			return err
@@ -96,7 +98,7 @@ func readMembersFromBackend(lg *zap.Logger, be backend.Backend) (map[types.ID]*M
 	}
 
 	err = tx.UnsafeForEach(membersRemovedBucketName, func(k, v []byte) error {
-		memberId := MustParseMemberIDFromBytes(lg, k)
+		memberId := mustParseMemberIDFromBytes(lg, k)
 		removed[memberId] = true
 		return nil
 	})
@@ -114,6 +116,8 @@ func mustReadMembersFromBackend(lg *zap.Logger, be backend.Backend) (map[types.I
 	return members, removed
 }
 
+// TrimMembershipFromBackend removes all information about members &
+// removed_members from the v3 backend.
 func TrimMembershipFromBackend(lg *zap.Logger, be backend.Backend) error {
 	tx := be.BatchTx()
 	tx.Lock()
@@ -135,6 +139,27 @@ func TrimMembershipFromBackend(lg *zap.Logger, be backend.Backend) error {
 	return nil
 }
 
+// TrimMembershipFromV2Store removes all information about members &
+// removed_members from the v2 store.
+func TrimMembershipFromV2Store(lg *zap.Logger, s v2store.Store) error {
+	members, removed := membersFromStore(lg, s)
+
+	for mID := range members {
+		_, err := s.Delete(MemberStoreKey(mID), true, true)
+		if err != nil {
+			return err
+		}
+	}
+	for mID := range removed {
+		_, err := s.Delete(RemovedMemberStoreKey(mID), true, true)
+		if err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
 func mustSaveClusterVersionToBackend(be backend.Backend, ver *semver.Version) {
 	ckey := backendClusterVersionKey()
 
@@ -289,7 +314,7 @@ func MemberAttributesStorePath(id types.ID) string {
 	return path.Join(MemberStoreKey(id), attributesSuffix)
 }
 
-func MustParseMemberIDFromBytes(lg *zap.Logger, key []byte) types.ID {
+func mustParseMemberIDFromBytes(lg *zap.Logger, key []byte) types.ID {
 	id, err := types.IDFromString(string(key))
 	if err != nil {
 		lg.Panic("failed to parse member id from key", zap.Error(err))