Merge pull request etcd-io#17151 from serathius/fix-bootstrap

[release-3.5] Fix etcd bootstrap: Etcd not validating database consistent index, closing database and panicking on nil backend.

server/etcdserver/server.go

@@ -35,6 +35,7 @@ import (
 	humanize "github.com/dustin/go-humanize"
 	"github.com/prometheus/client_golang/prometheus"
 	"go.etcd.io/etcd/server/v3/config"
+	"go.etcd.io/etcd/server/v3/wal/walpb"
 	"go.uber.org/zap"
 
 	pb "go.etcd.io/etcd/api/v3/etcdserverpb"
@@ -392,7 +393,7 @@ func NewServer(cfg config.ServerConfig) (srv *EtcdServer, err error) {
 	}
 
 	defer func() {
-		if err != nil {
+		if be != nil && err != nil {
 			be.Close()
 		}
 	}()
@@ -485,13 +486,14 @@ func NewServer(cfg config.ServerConfig) (srv *EtcdServer, err error) {
 		}
 
 		// Find a snapshot to start/restart a raft node
-		walSnaps, err := wal.ValidSnapshotEntries(cfg.Logger, cfg.WALDir())
+		var walSnaps []walpb.Snapshot
+		walSnaps, err = wal.ValidSnapshotEntries(cfg.Logger, cfg.WALDir())
 		if err != nil {
 			return nil, err
 		}
 		// snapshot files can be orphaned if etcd crashes after writing them but before writing the corresponding
 		// wal log entries
-		snapshot, err := ss.LoadNewestAvailable(walSnaps)
+		snapshot, err = ss.LoadNewestAvailable(walSnaps)
 		if err != nil && err != snap.ErrNoSnapshot {
 			return nil, err
 		}