fix: don't create value gc closer to avoid goroutine leak and add more ReadOnly guards on :

- Sync
- RunValueLogGC
- Flatten
- BanNamespace
- GetSequence

Author: Naelpuissant

db.go

@@ -378,7 +378,7 @@ func Open(opt Options) (*DB, error) {
 	db.closers.writes = z.NewCloser(1)
 	go db.doWrites(db.closers.writes)
 
-	if !db.opt.InMemory {
+	if !db.opt.InMemory && !db.opt.ReadOnly {
 		db.closers.valueGC = z.NewCloser(1)
 		go db.vlog.waitOnGC(db.closers.valueGC)
 	}
@@ -671,8 +671,8 @@ const (
 // Sync syncs database content to disk. This function provides
 // more control to user to sync data whenever required.
 func (db *DB) Sync() error {
-	if db.opt.InMemory {
-		// InMemory mode does not use WAL/vlog files, so Sync is a no-op.
+	if db.opt.InMemory || db.opt.ReadOnly {
+		// InMemory and read-only modes do not use WAL/vlog files, so Sync is a no-op.
 		return nil
 	}
 
@@ -1235,6 +1235,9 @@ func (db *DB) RunValueLogGC(discardRatio float64) error {
 	if db.opt.InMemory {
 		return ErrGCInMemoryMode
 	}
+	if db.opt.ReadOnly {
+		return ErrGCInReadOnlyMode
+	}
 	if discardRatio >= 1.0 || discardRatio <= 0.0 {
 		return ErrInvalidRequest
 	}
@@ -1355,6 +1358,9 @@ func (db *DB) GetSequence(key []byte, bandwidth uint64) (*Sequence, error) {
 	if db.opt.managedTxns {
 		panic("Cannot use GetSequence with managedDB=true.")
 	}
+	if db.opt.ReadOnly {
+		panic("Cannot use GetSequence in read-only mode.")
+	}
 
 	switch {
 	case len(key) == 0:
@@ -1563,6 +1569,9 @@ func (db *DB) startMemoryFlush() {
 // stopped. Ideally, no writes are going on during Flatten. Otherwise, it would create competition
 // between flattening the tree and new tables being created at level zero.
 func (db *DB) Flatten(workers int) error {
+	if db.opt.ReadOnly {
+		panic("Cannot flatten in read-only mode.")
+	}
 
 	db.stopCompactions()
 	defer db.startCompactions()
@@ -1851,6 +1860,9 @@ func (db *DB) BanNamespace(ns uint64) error {
 	if db.opt.NamespaceOffset < 0 {
 		return ErrNamespaceMode
 	}
+	if db.opt.ReadOnly {
+		panic("Cannot ban namespace in read-only mode.")
+	}
 	db.opt.Infof("Banning namespace: %d", ns)
 	// First set the banned namespaces in DB and then update the in-memory structure.
 	key := y.KeyWithTs(append(bannedNsKey, y.U64ToBytes(ns)...), 1)

db_test.go

@@ -1769,12 +1769,10 @@ func TestReadOnly(t *testing.T) {
 	opts.ReadOnly = true
 	kv1, err := Open(opts)
 	require.NoError(t, err)
-	defer kv1.Close()
 
 	// Open another read-only
 	kv2, err := Open(opts)
 	require.NoError(t, err)
-	defer kv2.Close()
 
 	// Attempt a read-write open while it's open for read-only
 	opts.ReadOnly = false
@@ -1791,6 +1789,10 @@ func TestReadOnly(t *testing.T) {
 	require.Equal(t, b1, []byte("value1"))
 	err = txn1.Commit()
 	require.NoError(t, err)
+	err = kv1.RunValueLogGC(0.5)
+	require.Error(t, err, ErrGCInReadOnlyMode)
+	err = kv1.Sync()
+	require.NoError(t, err)
 
 	// Get a thing from the DB via the other connection
 	txn2 := kv2.NewTransaction(true)
@@ -1809,6 +1811,26 @@ func TestReadOnly(t *testing.T) {
 	require.Contains(t, err.Error(), "No sets or deletes are allowed in a read-only transaction")
 	err = txn.Commit()
 	require.NoError(t, err)
+
+	// Close
+	require.NoError(t, kv1.Close())
+	require.NoError(t, kv2.Close())
+
+	// Test os permission read-only open
+	// We don't directly chmod the directory to still be able to aquire the lock
+	err = os.Chmod(dir, 0o500)
+	require.NoError(t, err)
+	opts.ReadOnly = true
+	kv3, err := Open(opts)
+	require.NoError(t, err)
+	txn3 := kv3.NewTransaction(true)
+	_, err = txn3.Get([]byte("key1"))
+	require.NoError(t, err)
+	require.NoError(t, kv3.Close())
+	require.NoError(t, txn3.Commit())
+
+	// Restore permissions for cleanup
+	require.NoError(t, os.Chmod(dir, 0o700))
 }
 
 func TestLSMOnly(t *testing.T) {

errors.go

@@ -109,6 +109,9 @@ var (
 	// ErrGCInMemoryMode is returned when db.RunValueLogGC is called in in-memory mode.
 	ErrGCInMemoryMode = stderrors.New("Cannot run value log GC when DB is opened in InMemory mode")
 
+	// ErrGCInReadOnlyMode is returned when db.RunValueLogGC is called in read-only mode.
+	ErrGCInReadOnlyMode = stderrors.New("Cannot run value log GC when DB is opened in ReadOnly mode")
+
 	// ErrDBClosed is returned when a get operation is performed after closing the DB.
 	ErrDBClosed = stderrors.New("DB Closed")
 )

value.go

@@ -1099,7 +1099,7 @@ func (vlog *valueLog) runGC(discardRatio float64) error {
 }
 
 func (vlog *valueLog) updateDiscardStats(stats map[uint32]int64) {
-	if vlog.opt.InMemory {
+	if vlog.opt.InMemory || vlog.opt.ReadOnly {
 		return
 	}
 	for fid, discard := range stats {