fix: 修复空周期流量规则列表导致流量历史清理失效 (#1226)

* fix: prevent unbounded transfer history growth

* fix: preserve transfer history on alert load errors

* test: close transfer cleanup database

---------

Co-authored-by: naiba <hi@nai.ba>

service/singleton/singleton.go

@@ -160,7 +160,10 @@ func CleanMonitorHistory() {
 	specialServerKeep := make(map[uint64]time.Time)
 	var specialServerIDs []uint64
 	var alerts []model.AlertRule
-	DB.Find(&alerts)
+	if err := DB.Find(&alerts).Error; err != nil {
+		log.Printf("NEZHA>> Failed to load alert rules while cleaning transfer history: %v", err)
+		return
+	}
 	for _, alert := range alerts {
 		for _, rule := range alert.Rules {
 			// 是不是流量记录规则
@@ -188,6 +191,14 @@ func CleanMonitorHistory() {
 	for id, couldRemove := range specialServerKeep {
 		DB.Unscoped().Delete(&model.Transfer{}, "server_id = ? AND datetime(`created_at`) < datetime(?)", id, couldRemove)
 	}
+	if len(specialServerIDs) == 0 {
+		if allServerKeep.IsZero() {
+			DB.Unscoped().Session(&gorm.Session{AllowGlobalUpdate: true}).Delete(&model.Transfer{})
+		} else {
+			DB.Unscoped().Delete(&model.Transfer{}, "datetime(`created_at`) < datetime(?)", allServerKeep)
+		}
+		return
+	}
 	if allServerKeep.IsZero() {
 		DB.Unscoped().Delete(&model.Transfer{}, "server_id NOT IN (?)", specialServerIDs)
 	} else {