p2p: panic in enode DB Close on shutdown (#9237) (#9240)

If any DB method is called while Close() is waiting for db.kv.Close()
(it waits for ongoing method calls/transactions to finish)
a panic: "WaitGroup is reused before previous Wait has returned" might
happen.

Use context cancellation to ensure that new method calls immediately
return during db.kv.Close().

p2p/enode/nodedb.go

@@ -29,14 +29,13 @@ import (
 	"time"
 
 	"github.com/c2h5oh/datasize"
+	mdbx1 "github.com/erigontech/mdbx-go/mdbx"
+	"github.com/ledgerwatch/log/v3"
+
 	libcommon "github.com/ledgerwatch/erigon-lib/common"
 	"github.com/ledgerwatch/erigon-lib/kv"
 	"github.com/ledgerwatch/erigon-lib/kv/mdbx"
-
 	"github.com/ledgerwatch/erigon/rlp"
-	"github.com/ledgerwatch/log/v3"
-
-	mdbx1 "github.com/erigontech/mdbx-go/mdbx"
 )
 
 // Keys in the node database.
@@ -77,14 +76,16 @@ var zeroIP = make(net.IP, 16)
 type DB struct {
 	kv     kv.RwDB   // Interface to the database itself
 	runner sync.Once // Ensures we can start at most one expirer
-	quit   chan struct{} // Channel to signal the expiring thread to stop
+
+	ctx       context.Context
+	ctxCancel func()
 }
 
 // OpenDB opens a node database for storing and retrieving infos about known peers in the
 // network. If no path is given an in-memory, temporary database is constructed.
 func OpenDB(ctx context.Context, path string, tmpDir string, logger log.Logger) (*DB, error) {
 	if path == "" {
-		return newMemoryDB(logger, tmpDir)
+		return newMemoryDB(ctx, logger, tmpDir)
 	}
 	return newPersistentDB(ctx, logger, path)
 }
@@ -97,22 +98,27 @@ func bucketsConfig(_ kv.TableCfg) kv.TableCfg {
 }
 
 // newMemoryNodeDB creates a new in-memory node database without a persistent backend.
-func newMemoryDB(logger log.Logger, tmpDir string) (*DB, error) {
+func newMemoryDB(ctx context.Context, logger log.Logger, tmpDir string) (*DB, error) {
-	db := &DB{quit: make(chan struct{})}
+	db, err := mdbx.NewMDBX(logger).
-	var err error
+		InMem(tmpDir).
-	db.kv, err = mdbx.NewMDBX(logger).InMem(tmpDir).Label(kv.SentryDB).WithTableCfg(bucketsConfig).MapSize(1 * datasize.GB).Open(context.Background())
+		Label(kv.SentryDB).
+		WithTableCfg(bucketsConfig).
+		MapSize(1 * datasize.GB).
+		Open(ctx)
 	if err != nil {
 		return nil, err
 	}
-	return db, nil
+
+	nodeDB := &DB{kv: db}
+	nodeDB.ctx, nodeDB.ctxCancel = context.WithCancel(ctx)
+
+	return nodeDB, nil
 }
 
 // newPersistentNodeDB creates/opens a persistent node database,
 // also flushing its contents in case of a version mismatch.
 func newPersistentDB(ctx context.Context, logger log.Logger, path string) (*DB, error) {
-	var db kv.RwDB
+	db, err := mdbx.NewMDBX(logger).
-	var err error
-	db, err = mdbx.NewMDBX(logger).
 		Path(path).
 		Label(kv.SentryDB).
 		WithTableCfg(bucketsConfig).
@@ -125,13 +131,14 @@ func newPersistentDB(ctx context.Context, logger log.Logger, path string) (*DB,
 	if err != nil {
 		return nil, err
 	}
+
 	// The nodes contained in the cache correspond to a certain protocol version.
 	// Flush all nodes if the version doesn't match.
 	currentVer := make([]byte, binary.MaxVarintLen64)
 	currentVer = currentVer[:binary.PutVarint(currentVer, int64(dbVersion))]
 
 	var blob []byte
-	if err := db.Update(context.Background(), func(tx kv.RwTx) error {
+	if err := db.Update(ctx, func(tx kv.RwTx) error {
 		c, err := tx.RwCursor(kv.Inodes)
 		if err != nil {
 			return err
@@ -150,6 +157,7 @@ func newPersistentDB(ctx context.Context, logger log.Logger, path string) (*DB,
 	}); err != nil {
 		return nil, err
 	}
+
 	if blob != nil && !bytes.Equal(blob, currentVer) {
 		db.Close()
 		if err := os.RemoveAll(path); err != nil {
@@ -157,7 +165,11 @@ func newPersistentDB(ctx context.Context, logger log.Logger, path string) (*DB,
 		}
 		return newPersistentDB(ctx, logger, path)
 	}
-	return &DB{kv: db, quit: make(chan struct{})}, nil
+
+	nodeDB := &DB{kv: db}
+	nodeDB.ctx, nodeDB.ctxCancel = context.WithCancel(ctx)
+
+	return nodeDB, nil
 }
 
 // nodeKey returns the database key for a node record.
@@ -227,7 +239,7 @@ func localItemKey(id ID, field string) []byte {
 // fetchInt64 retrieves an integer associated with a particular key.
 func (db *DB) fetchInt64(key []byte) int64 {
 	var val int64
-	if err := db.kv.View(context.Background(), func(tx kv.Tx) error {
+	if err := db.kv.View(db.ctx, func(tx kv.Tx) error {
 		blob, errGet := tx.GetOne(kv.Inodes, key)
 		if errGet != nil {
 			return errGet
@@ -249,7 +261,7 @@ func (db *DB) fetchInt64(key []byte) int64 {
 func (db *DB) storeInt64(key []byte, n int64) error {
 	blob := make([]byte, binary.MaxVarintLen64)
 	blob = blob[:binary.PutVarint(blob, n)]
-	return db.kv.Update(context.Background(), func(tx kv.RwTx) error {
+	return db.kv.Update(db.ctx, func(tx kv.RwTx) error {
 		return tx.Put(kv.Inodes, libcommon.CopyBytes(key), blob)
 	})
 }
@@ -257,7 +269,7 @@ func (db *DB) storeInt64(key []byte, n int64) error {
 // fetchUint64 retrieves an integer associated with a particular key.
 func (db *DB) fetchUint64(key []byte) uint64 {
 	var val uint64
-	if err := db.kv.View(context.Background(), func(tx kv.Tx) error {
+	if err := db.kv.View(db.ctx, func(tx kv.Tx) error {
 		blob, errGet := tx.GetOne(kv.Inodes, key)
 		if errGet != nil {
 			return errGet
@@ -276,7 +288,7 @@ func (db *DB) fetchUint64(key []byte) uint64 {
 func (db *DB) storeUint64(key []byte, n uint64) error {
 	blob := make([]byte, binary.MaxVarintLen64)
 	blob = blob[:binary.PutUvarint(blob, n)]
-	return db.kv.Update(context.Background(), func(tx kv.RwTx) error {
+	return db.kv.Update(db.ctx, func(tx kv.RwTx) error {
 		return tx.Put(kv.Inodes, libcommon.CopyBytes(key), blob)
 	})
 }
@@ -284,7 +296,7 @@ func (db *DB) storeUint64(key []byte, n uint64) error {
 // Node retrieves a node with a given id from the database.
 func (db *DB) Node(id ID) *Node {
 	var blob []byte
-	if err := db.kv.View(context.Background(), func(tx kv.Tx) error {
+	if err := db.kv.View(db.ctx, func(tx kv.Tx) error {
 		v, errGet := tx.GetOne(kv.NodeRecords, nodeKey(id))
 		if errGet != nil {
 			return errGet
@@ -322,7 +334,7 @@ func (db *DB) UpdateNode(node *Node) error {
 	if err != nil {
 		return err
 	}
-	if err := db.kv.Update(context.Background(), func(tx kv.RwTx) error {
+	if err := db.kv.Update(db.ctx, func(tx kv.RwTx) error {
 		return tx.Put(kv.NodeRecords, nodeKey(node.ID()), blob)
 	}); err != nil {
 		return err
@@ -346,11 +358,11 @@ func (db *DB) Resolve(n *Node) *Node {
 
 // DeleteNode deletes all information associated with a node.
 func (db *DB) DeleteNode(id ID) {
-	deleteRange(db.kv, nodeKey(id))
+	db.deleteRange(nodeKey(id))
 }
 
-func deleteRange(db kv.RwDB, prefix []byte) {
+func (db *DB) deleteRange(prefix []byte) {
-	if err := db.Update(context.Background(), func(tx kv.RwTx) error {
+	if err := db.kv.Update(db.ctx, func(tx kv.RwTx) error {
 		for bucket := range bucketsConfig(nil) {
 			if err := deleteRangeInBucket(tx, prefix, bucket); err != nil {
 				return err
@@ -398,7 +410,7 @@ func (db *DB) expirer() {
 		select {
 		case <-tick.C:
 			db.expireNodes()
-		case <-db.quit:
+		case <-db.ctx.Done():
 			return
 		}
 	}
@@ -412,7 +424,7 @@ func (db *DB) expireNodes() {
 		youngestPong int64
 	)
 	var toDelete [][]byte
-	if err := db.kv.View(context.Background(), func(tx kv.Tx) error {
+	if err := db.kv.View(db.ctx, func(tx kv.Tx) error {
 		c, err := tx.Cursor(kv.Inodes)
 		if err != nil {
 			return err
@@ -455,7 +467,7 @@ func (db *DB) expireNodes() {
 		log.Warn("nodeDB.expireNodes failed", "err", err)
 	}
 	for _, td := range toDelete {
-		deleteRange(db.kv, td)
+		db.deleteRange(td)
 	}
 }
 
@@ -545,7 +557,7 @@ func (db *DB) QuerySeeds(n int, maxAge time.Duration) []*Node {
 		id    ID
 	)
 
-	if err := db.kv.View(context.Background(), func(tx kv.Tx) error {
+	if err := db.kv.View(db.ctx, func(tx kv.Tx) error {
 		c, err := tx.Cursor(kv.NodeRecords)
 		if err != nil {
 			return err
@@ -603,14 +615,6 @@ func (db *DB) QuerySeeds(n int, maxAge time.Duration) []*Node {
 
 // close flushes and closes the database files.
 func (db *DB) Close() {
-	select {
+	db.ctxCancel()
-	case <-db.quit:
-		return // means closed already
-	default:
-	}
-	if db.quit == nil {
-		return
-	}
-	libcommon.SafeClose(db.quit)
 	db.kv.Close()
 }