Finisky Garden

The double-spending problem is a critical challenge in transaction systems, especially when managing account balances or funds. It occurs when a system allows the same funds to be spent multiple times due to concurrent operations or race conditions. In this article, we explore two approaches to resolving this issue using MongoDB: transaction-based handling and versioning-based handling.

This post is an in-depth discussion of the double-spending problem from the Building a Transaction System with MongoDB blog.

双花问题是交易系统中的一个关键挑战，尤其是在管理账户余额或资金时。当系统允许由于并发操作或竞争条件导致同一笔资金被多次使用时，就会发生双花问题。本文将探讨使用 MongoDB 解决这一问题的两种方法：基于事务的处理和基于版本的处理。

本文是用MongoDB构建交易系统关于双花问题的深入讨论。

After a Windows Update, RDP on Windows 11 might stop working correctly. Symptoms include a black screen upon connection, no visible mouse or interface, and an automatic disconnection after about a minute. This forces users to return to the local machine to investigate the issue.

Windows Update之后，win11的远程桌面就不好使了：连接黑屏，鼠标和界面一概不可见，一分钟之后自动断开连接。无奈只能重新进入本机查看到底是什么问题。

If you’ve ever struggled to set the correct timezone for your cron jobs on Ubuntu 22.04, you’re not alone. In this blog, we’ll walk you through a troubleshooting journey that highlights common pitfalls and the ultimate solution.

When working with Azure Virtual Machines (VMs), monitoring performance metrics is essential for ensuring optimal operation. A common scenario involves tracking the CPU Credits Remaining for a B-series burstable VM instance.

Typically, we use az vm monitor metrics tail to get the CPU Credits Remaining metric:

Transaction systems are at the heart of modern commerce and financial activities, spanning a wide range of scenarios from e-commerce order processing to real-time settlements in financial institutions. Such systems demand high concurrency handling, real-time data storage, and efficient retrieval capabilities, all while balancing data consistency and performance. As transaction data continues to grow in scale and complexity, traditional transaction system architectures often struggle to meet these challenges due to rigid table structures and limited horizontal scalability.

MongoDB, as a distributed document-oriented database, provides a modern solution for building complex and efficient transaction systems. With its flexible schema design, high throughput capabilities, and built-in transaction support, MongoDB addresses diverse business needs effectively.

交易系统是现代商业和金融活动的核心，涵盖从电子商务订单处理到金融机构的实时清算等多种场景。这类系统通常需要高并发处理能力、实时数据存储和高效检索功能，同时需要在数据一致性与性能之间找到平衡。随着交易数据的规模和复杂性不断增长，传统交易系统架构在应对这些挑战时，往往因固定的表结构和横向扩展能力的不足而受限。

MongoDB 作为一款分布式文档型数据库，以其灵活的架构、高吞吐能力和内置的事务支持，为构建复杂、高效的交易系统提供了一种现代化的解决方案，能够满足多样化的业务需求。

Received a certificate renewal notification from Tencent Cloud, but when applying for a new certificate, I found out that Tencent Cloud no longer offers free one-year certificates:

Starting from April 25, 2024, the validity period of new free certificates issued by Tencent Cloud will be adjusted to 90 days.

Since I’ve always updated certificates manually, doing it every three months feels quite tedious. So, I decided to explore Certbot from Let's Encrypt. My only concern was how to prove ownership of a subdomain. After trying it out, I realized this wasn’t an issue at all, as Certbot only issues certificates and doesn’t pose any threat to the website itself.

Here are the configuration steps for Certbot. In fact, it’s very simple and only requires running a few commands.

收到腾讯云的证书续期通知，结果在申请新证书时发现，腾讯云不再支持一年的免费证书：

2024年4月25日起，腾讯云新签发的免费证书有效期调整为 90 天

考虑到一直是手动更新证书，如果三个月手动操作一次还是挺费劲的。于是研究Let's Encrypt的certbot，唯一的顾虑是如何证明自己对二级域名的所有权问题。实践之后发现此问题并不存在，因为certbot仅是签发一个证书而已，并不存在对网站本身的威胁。

下面是certbot的配置步骤，其实仅需要执行几个命令，非常简单。