台风天MySQL CPU两度“爆表”：从升配到揪出死循环代码的24小时追凶记

// 存在死循环风险的钱包记录查询函数
func (l *WalletRecord) Do() (resp WalletRecordRsp, err error) {
pageSize := 10
resp = WalletRecordRsp{} 
// 初始化查询参数
nextIndex := l.req.StartIndex

// 主循环：直到获取到足够的记录
for len(resp.Records) < pageSize {
    // 如果有下一页索引，则使用它
    if resp.NextIndex > 0 {
        nextIndex = resp.NextIndex
    }

    // 查询数据库获取记录列表
    var recordList []UserRecord
    recordList, resp.NextIndex, err = QueryUserRecord(nextIndex, pageSize)
    if err != nil {
        return
    }

    // 遍历并处理每条记录
    for _, record := range recordList {
        // 过滤某些不需要显示的记录类型
        if shouldFilterRecord(record) {
            continue
        }

        // 构造返回结果
        item := &WalletRecord{
            Type:       record.Type,
            Amount:     amount,
            RecordTime: record.RecordTime.Unix(),
        }
        resp.Records = append(resp.Records, item)

        // 如果已经达到页面大小，保存下一个索引并跳出
        if len(resp.Records) == pageSize {
            resp.NextIndex = record.ID
            break
        }
    }

    // 如果返回的记录数少于页面大小，说明已经到最后一页
    if len(recordList) < pageSize {
        resp.NextIndex = 0
        return
    }
}
return
}

// 数据库查询函数
func QueryUserRecord(startIndex uint64, pageSize int) ([]UserRecord, uint64, error) {
var (
recordList []UserRecord
nextIndex uint64
) 
// 执行数据库查询
if startIndex == 0 {
    // 第一页查询
    rows, _ := db.Raw("SELECT * FROM records ORDER BY id DESC LIMIT ?", pageSize).Rows()
    defer rows.Close()
    
    for rows.Next() {
        data := UserRecord{}
        rows.Scan(&data.ID, &data.Type, &data.Amount, &data.RecordTime)
        nextIndex = data.ID
        recordList = append(recordList, data)
        
        if len(recordList) >= pageSize {
            break
        }
    }
} else {
    // 分页查询
    rows, _ := db.Raw("SELECT * FROM records WHERE id < ? ORDER BY id DESC LIMIT ?", 
                     startIndex, pageSize).Rows()
    defer rows.Close()
    
    for rows.Next() {
        data := UserRecord{}
        rows.Scan(&data.ID, &data.Type, &data.Amount, &data.RecordTime)
        nextIndex = data.ID
        recordList = append(recordList, data)
        
        if len(recordList) >= pageSize {
            break
        }
    }
}

return recordList, nextIndex, nil
}