Fix some cgo memory leaks

raftwal/wal.go

@@ -89,6 +89,7 @@ func (w *Wal) Store(gid uint32, s raftpb.Snapshot, h raftpb.HardState, es []raft
 		start := w.entryKey(gid, t, i+1)
 		prefix := w.prefix(gid)
 		itr := w.wals.NewIterator()
+		defer itr.Close()
 
 		for itr.Seek(start); itr.ValidForPrefix(prefix); itr.Next() {
 			b.Delete(itr.Key().Data())
@@ -123,6 +124,7 @@ func (w *Wal) Entries(gid uint32, fromTerm, fromIndex uint64) (es []raftpb.Entry
 	start := w.entryKey(gid, fromTerm, fromIndex)
 	prefix := w.prefix(gid)
 	itr := w.wals.NewIterator()
+	defer itr.Close()
 
 	for itr.Seek(start); itr.ValidForPrefix(prefix); itr.Next() {
 		data := itr.Value().Data()

rdb/db.go

@@ -66,7 +66,8 @@ func (db *DB) Close() {
 	C.rdb_close(db.c)
 }
 
-// Get returns the data associated with the key from the database.
+// Get returns the data associated with the key from the database. Remember
+// to deallocate the returned Slice.
 func (db *DB) Get(opts *ReadOptions, key []byte) (*Slice, error) {
 	var (
 		cErr    *C.char

worker/predicate.go

@@ -36,6 +36,7 @@ const (
 // writeBatch performs a batch write of key value pairs to RocksDB.
 func writeBatch(ctx context.Context, kv chan *task.KV, che chan error) {
 	wb := pstore.NewWriteBatch()
+	defer wb.Destroy()
 	batchSize := 0
 	batchWriteNum := 1
 	for i := range kv {