fix pooled db concurrency bug

client/dtmcli/dtmimp/utils.go

@@ -151,21 +151,31 @@ func MayReplaceLocalhost(host string) string {
 	return host
 }
 
-var sqlDbs sync.Map
+var sqlDbs = &mapCache{cache: map[string]*sql.DB{}}
 
-// PooledDB get pooled sql.DB
-func PooledDB(conf DBConf) (*sql.DB, error) {
+type mapCache struct {
+	mutex sync.Mutex
+	cache map[string]*sql.DB
+}
+
+func (m *mapCache) LoadOrStore(conf DBConf, factory func(conf DBConf) (*sql.DB, error)) (*sql.DB, error) {
+	m.mutex.Lock()
+	defer m.mutex.Unlock()
 	dsn := GetDsn(conf)
-	db, ok := sqlDbs.Load(dsn)
-	if !ok {
-		db2, err := StandaloneDB(conf)
-		if err != nil {
-			return nil, err
-		}
-		db = db2
-		sqlDbs.Store(dsn, db)
+	if db, ok := m.cache[dsn]; ok {
+		return db, nil
 	}
-	return db.(*sql.DB), nil
+	db, err := factory(conf)
+	if err != nil {
+		return nil, err
+	}
+	m.cache[dsn] = db
+	return db, nil
+}
+
+// PooledDB get pooled sql.DB
+func PooledDB(conf DBConf) (*sql.DB, error) {
+	return sqlDbs.LoadOrStore(conf, StandaloneDB)
 }
 
 // StandaloneDB get a standalone db instance