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.