[优化] 添加 Relay frps 连接和代理计数字段，重构相关逻辑以支持监控和可观测性

openflare_server/model/migrate/v20.go

@@ -0,0 +1,52 @@
+// v20 records low-frequency Relay frps counters on nodes so the management UI
+// can show whether the relay runtime is alive and reporting tunnel load.
+package migrate
+
+import (
+	"fmt"
+
+	"gorm.io/gorm"
+)
+
+type nodeV20 struct {
+	ID                   uint `gorm:"primaryKey"`
+	RelayFrpsConnections int  `gorm:"column:relay_frps_connections"`
+	RelayFrpsProxyCount  int  `gorm:"column:relay_frps_proxy_count"`
+}
+
+func (nodeV20) TableName() string {
+	return "nodes"
+}
+
+func init() {
+	Register(V20())
+}
+
+func V20() Migration {
+	return Migration{
+		FromVersion: 19,
+		ToVersion:   20,
+		Migrate:     migrateV20,
+		Validate:    validateV20,
+	}
+}
+
+func migrateV20(ctx Context, db *gorm.DB, backend string) error {
+	if err := ctx.ApplyCurrentSchema(db, backend); err != nil {
+		return err
+	}
+	return validateV20(ctx, db, backend)
+}
+
+func validateV20(ctx Context, db *gorm.DB, backend string) error {
+	if err := ctx.ValidateDatabaseSchemaVersion(db, backend, 19); err != nil {
+		return err
+	}
+	if !db.Migrator().HasColumn(&nodeV20{}, "relay_frps_connections") {
+		return fmt.Errorf("column nodes.relay_frps_connections is missing")
+	}
+	if !db.Migrator().HasColumn(&nodeV20{}, "relay_frps_proxy_count") {
+		return fmt.Errorf("column nodes.relay_frps_proxy_count is missing")
+	}
+	return nil
+}