Table of Contents
回复内容:
Home Backend Development PHP Tutorial 如何设计可离线工作的软件的同步功能

如何设计可离线工作的软件的同步功能

Jun 06, 2016 pm 08:38 PM
php Synchronize Architecture design

有很多软件在没有接入网络的情况下也可以运行,等到有网络时,会进行数据同步。这样在多个客户端间可以无缝所有。

典型代表:有道云笔记挖财记账本

目前,我使用php开发一款软件的服务端,软件提供网页版和客户端。在离线状态下,客户端主要功能也是可以使用的。

现在采用的方案是:
用C语言写了一个php的扩展,用于生成唯一int64值
需要同步的数据表,都添加了一个字段modify_num,存放唯一int64值,对数据记录进行增删改时,都改变modify_num。

客户端定时执行同步操作,每次同步包含2个原子操作:先是客户端给服务端自己最大的modify_num,服务端把大于该modify_num的数据都返回给客户端,简称为update;然后客户端处理完数据后,把客户端需要进行增删改的数据发送给服务端,服务端进行处理,简称为commit

补充:
1.为什么modify_num不直接使用时间戳,而是唯一数值:

我们没有直接采用时间戳是有原因的:操作时间间隔太短的时候,产生的时间戳会是相同的数值。如果不唯一会有这样的情况发生,在update时服务端返回了多条modify_num相同的数据给客户端,客户端每处理一条就修改自己的最大modify_num,万一客户端以为外因崩溃,多条数据没有处理完,下次启动时发送的最大modify_num给服务端,那么服务端返回的是大于这个值的数据,意味着那几条因为崩溃没有处理的数据都没有拿到。采用唯一数值就是为了避免这种情况发生。

2.关于冲突处理:

毕竟我们面对的是普通用户,不是程序员,不会像版本管理工具一样,有合并冲突的功能,冲突我们有自己的一套简单机制。基本原则是以modify_num大的优先,以最后操作优先。

大家有没有更好的方案或者有什么想法,都可以说说

回复内容:

有很多软件在没有接入网络的情况下也可以运行,等到有网络时,会进行数据同步。这样在多个客户端间可以无缝所有。

典型代表:有道云笔记挖财记账本

目前,我使用php开发一款软件的服务端,软件提供网页版和客户端。在离线状态下,客户端主要功能也是可以使用的。

现在采用的方案是:
用C语言写了一个php的扩展,用于生成唯一int64值
需要同步的数据表,都添加了一个字段modify_num,存放唯一int64值,对数据记录进行增删改时,都改变modify_num。

客户端定时执行同步操作,每次同步包含2个原子操作:先是客户端给服务端自己最大的modify_num,服务端把大于该modify_num的数据都返回给客户端,简称为update;然后客户端处理完数据后,把客户端需要进行增删改的数据发送给服务端,服务端进行处理,简称为commit

补充:
1.为什么modify_num不直接使用时间戳,而是唯一数值:

我们没有直接采用时间戳是有原因的:操作时间间隔太短的时候,产生的时间戳会是相同的数值。如果不唯一会有这样的情况发生,在update时服务端返回了多条modify_num相同的数据给客户端,客户端每处理一条就修改自己的最大modify_num,万一客户端以为外因崩溃,多条数据没有处理完,下次启动时发送的最大modify_num给服务端,那么服务端返回的是大于这个值的数据,意味着那几条因为崩溃没有处理的数据都没有拿到。采用唯一数值就是为了避免这种情况发生。

2.关于冲突处理:

毕竟我们面对的是普通用户,不是程序员,不会像版本管理工具一样,有合并冲突的功能,冲突我们有自己的一套简单机制。基本原则是以modify_num大的优先,以最后操作优先。

大家有没有更好的方案或者有什么想法,都可以说说

modify_num干脆改成last_modify比较直观,内容就是最后一次修改时间戳,这样同步的时候带上上次同步完的时间戳,服务器把上次同步之后所有更改发回。

两边都维护了一个num,冲突解决如何处理?
如果最初版本值为0,在网页端和离线客户端编辑,
同步时,服务器端和客户端的版本值都为1;
这就是涉及到冲突问题的解决,你说客户端先把大于
1的值更新,这时候服务器的值也是1,但是内容是变化了的;

可以考虑使用类似数据库的redo日志;
服务器和客户端数据修改前都记录日志(含精确的时间戳);
在客户端联网后,先将客户端离线期间的日志发送到服务器端,
服务器端按时间点插入日志(客户端服务端日志合并),redo日志;
然后,将数据同步到客户端;

应该参考git软件内部的实现,有冲突的时候分为可以自动合并和不可以自动合并

merge对于普通用户门槛太高 让用户选择一个版本基本就够了 其实最简单的方法就是让用户接受开机自启动 不知不觉完成同步,。,

Statement of this Website
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn

Hot AI Tools

Undresser.AI Undress

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

AI Clothes Remover

Online AI tool for removing clothes from photos.

Undress AI Tool

Undress AI Tool

Undress images for free

Clothoff.io

Clothoff.io

AI clothes remover

Video Face Swap

Video Face Swap

Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Tools

Notepad++7.3.1

Notepad++7.3.1

Easy-to-use and free code editor

SublimeText3 Chinese version

SublimeText3 Chinese version

Chinese version, very easy to use

Zend Studio 13.0.1

Zend Studio 13.0.1

Powerful PHP integrated development environment

Dreamweaver CS6

Dreamweaver CS6

Visual web development tools

SublimeText3 Mac version

SublimeText3 Mac version

God-level code editing software (SublimeText3)

PHP 8.4 Installation and Upgrade guide for Ubuntu and Debian PHP 8.4 Installation and Upgrade guide for Ubuntu and Debian Dec 24, 2024 pm 04:42 PM

PHP 8.4 brings several new features, security improvements, and performance improvements with healthy amounts of feature deprecations and removals. This guide explains how to install PHP 8.4 or upgrade to PHP 8.4 on Ubuntu, Debian, or their derivati

How To Set Up Visual Studio Code (VS Code) for PHP Development How To Set Up Visual Studio Code (VS Code) for PHP Development Dec 20, 2024 am 11:31 AM

Visual Studio Code, also known as VS Code, is a free source code editor — or integrated development environment (IDE) — available for all major operating systems. With a large collection of extensions for many programming languages, VS Code can be c

7 PHP Functions I Regret I Didn't Know Before 7 PHP Functions I Regret I Didn't Know Before Nov 13, 2024 am 09:42 AM

If you are an experienced PHP developer, you might have the feeling that you’ve been there and done that already.You have developed a significant number of applications, debugged millions of lines of code, and tweaked a bunch of scripts to achieve op

Explain JSON Web Tokens (JWT) and their use case in PHP APIs. Explain JSON Web Tokens (JWT) and their use case in PHP APIs. Apr 05, 2025 am 12:04 AM

JWT is an open standard based on JSON, used to securely transmit information between parties, mainly for identity authentication and information exchange. 1. JWT consists of three parts: Header, Payload and Signature. 2. The working principle of JWT includes three steps: generating JWT, verifying JWT and parsing Payload. 3. When using JWT for authentication in PHP, JWT can be generated and verified, and user role and permission information can be included in advanced usage. 4. Common errors include signature verification failure, token expiration, and payload oversized. Debugging skills include using debugging tools and logging. 5. Performance optimization and best practices include using appropriate signature algorithms, setting validity periods reasonably,

How do you parse and process HTML/XML in PHP? How do you parse and process HTML/XML in PHP? Feb 07, 2025 am 11:57 AM

This tutorial demonstrates how to efficiently process XML documents using PHP. XML (eXtensible Markup Language) is a versatile text-based markup language designed for both human readability and machine parsing. It's commonly used for data storage an

PHP Program to Count Vowels in a String PHP Program to Count Vowels in a String Feb 07, 2025 pm 12:12 PM

A string is a sequence of characters, including letters, numbers, and symbols. This tutorial will learn how to calculate the number of vowels in a given string in PHP using different methods. The vowels in English are a, e, i, o, u, and they can be uppercase or lowercase. What is a vowel? Vowels are alphabetic characters that represent a specific pronunciation. There are five vowels in English, including uppercase and lowercase: a, e, i, o, u Example 1 Input: String = "Tutorialspoint" Output: 6 explain The vowels in the string "Tutorialspoint" are u, o, i, a, o, i. There are 6 yuan in total

Explain late static binding in PHP (static::). Explain late static binding in PHP (static::). Apr 03, 2025 am 12:04 AM

Static binding (static::) implements late static binding (LSB) in PHP, allowing calling classes to be referenced in static contexts rather than defining classes. 1) The parsing process is performed at runtime, 2) Look up the call class in the inheritance relationship, 3) It may bring performance overhead.

What are PHP magic methods (__construct, __destruct, __call, __get, __set, etc.) and provide use cases? What are PHP magic methods (__construct, __destruct, __call, __get, __set, etc.) and provide use cases? Apr 03, 2025 am 12:03 AM

What are the magic methods of PHP? PHP's magic methods include: 1.\_\_construct, used to initialize objects; 2.\_\_destruct, used to clean up resources; 3.\_\_call, handle non-existent method calls; 4.\_\_get, implement dynamic attribute access; 5.\_\_set, implement dynamic attribute settings. These methods are automatically called in certain situations, improving code flexibility and efficiency.

See all articles