Mysql 內部結構 / Replication

Chapter 19 Replication

Table of Contents     

19.1 Chapter Organization

19.2 Source Code Files

19.3 Principles     

19.4 Rules     

Status of this section: up to date 2009-10-21

This chapter describes MySQL replication principles, rules, and code, as it is supposed to work in version 5.1.

The MySQL replication feature allows a server - the master - to send all changes to another server - the slave - and the slave tries to apply all changes to keep up-to-date with the master. Replication works as follows:

• Whenever the master's database is modified, the change is written to a file, the so-called binary log, or binlog. This is done by the client thread that executed the query that modified the database.

• The master has a thread, called the dump thread, that continuously reads the master's binlog and sends it to the slave.

• The slave has a thread, called the IO thread, that receives the binlog that the master's dump thread sent, and writes it to a file: the relay log.

• The slave has another thread, called the SQL thread, that continuously reads the relay log and applies the changes to the slave server.

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19.1 層次結構 

19.2 源代碼文件

19.3 原理     

19.4 規則     

本節狀態：最新2009-10-21

本章介紹了MySQL複製的原則，規則和代碼。它應該用在5.1版本上。

MySQL的複製功能容許服務器- master -發送的全部更改到另外一臺服務器-的slave -和slave試圖以應用全部更新操做，以便跟上最新的master。複製的工做原理以下：

• 每當master的數據庫修改，更改寫入到文件中，即所謂的二進制日誌或binlog。這些內容是由客戶端線程執行數據庫查詢（這裏的查詢是統稱，實際上只會保留DML，select並不保存）的。

• master上有一個線程，稱爲dump thread，即連續讀取主的二進制日誌，並將其發送到slave。

• slave有一個線程，稱爲IO線程（IO thread），接收了master的dump thread發送的二進制日誌，並將其寫入文件：在 中繼日誌（relay log）。

• slave上有另外一個線程，稱爲 SQL線程（SQL thread），即連續讀取中繼日誌並應用更改到slave的數據庫上。