MySQL master-slave replication solves read-write separation

The concept of separation of reading and writing

All the pressure of reading and writing is borne by one database , The data will be lost if the database service disk is damaged due to high pressure , A single point of failure

mysql Master-slave replication of can solve this problem

Introduce

MySQL Master-slave replication is an asynchronous replication process , The bottom layer is based on Mysql Binary log function of database . Just one or more Mysql database (slave, From the library ) From the other Mysql database (master, The main library ) Copy the log, then parse the log and apply it to itself , Finally, the data of the slave database is consistent with that of the master database .Mysql Principal and subordinate malfeasance is MySql The database has its own functions , No third party tools required .

mysql The replication process is divided into three steps

master Log changes to binary log （binary log）

slave take master Of binary log Copy to his relay log （relay log）

slave Redo relay log events , Apply the changes to your own database

To configure - precondition

Prepare two servers in advance , Install separately mysql And start the service successfully

Main library master

First step ： modify Mysql Profile of the database /etc/my.cnf

[mysqld]
log-bin=mysql-bin  #[ must ] Enable binary logging 
server-id=100      #[ must ] The server is unique ID

The second step ： restart mysql service

systemctl restart mysqld

The third step ： Sign in Mysql database , Do the following SQL

GRANT REPLICATION SLAVE ON *.* to 'xiaoming'@'%' identified by '[email protected]';

notes ： above SQL The role of is to create a xiaoming, The password for [email protected], And give xiaoming User grants REPLICATION SLAVE jurisdiction . It is often used to establish the user permissions required for replication , That is to say slave Must be master Authorize the user with this permission , Can be copied by this user .

Step four ： Sign in mysql data , Do the following SQL, Record the results File and Position Value

show master status;
 notes ： above SQL View when Master The state of , After that SQL Do not perform any more operations 

Slave Library slave

First step ： modify mysql Profile of the database /etc/my.cnf

[mysqld]
server-id=100      #[ must ] The server is unique ID

The second step ： restart mysql service

systemctl restart mysqld

The third step ： Sign in Mysql database , Do the following SQL

change master to master_host='192.168.138.100',master_user='xiaoming',master_password='[email protected]',master_log_file='mysql-bin.000001',master_log_pos=439;

start slave;

Step four ： Sign in Mysql database , Do the following SQL, View the status of the slave database

show slave status;

The cause of the error

1. The Internet is not working 2. The password is wrong 3.pos incorrect 4. The firewall is not off 5.server-id Conflict

If you use clone virtual machines , Must be modified mysql Of uuid, Otherwise it will show Slave_IO_Running: No

terms of settlement ：

1. First of all mysql Installation address of

show variables like 'datadir';
# adopt MySQL Generate a uuid Recording, etc. will be used to modify 
select uuid

2. Then enter datadir Catalog

cd /var/lib/mysql/
vi auto.cnf
 Take what you have just prepared uuid Value substitution 

3. restart mysql

systemctl start mysqld