Mysql主从
主从简介
主从复制也叫主从同步，用于备份数据防止意外，一台数据库存放数据有丢失风险，所以需要有多台数据库来保障安全。
主从作用
-
实时灾备，用于故障切换
-
读写分离，提供查询服务
-
备份，避免影响业务
主从形式
- 一主一从
- 主主复制
- 一主多从---（扩展系统读取的性能，因为读是在从库读取的）
- 多主一从
- 联级复制
主从复制原理
主从复制步骤：
主库将所有的写操作记录到binlog日志中并生成一个log dump线程，将binlog日志传给从库的I/O线程
从库生成两个线程，一个I/O线程，一个SQL线程
I/O线程去请求主库的binlog，并将得到的binlog日志写到relay log（中继日志） 文件中
SQL线程，会读取relay log文件中的日志，并解析成具体操作重放，来实现主从的操作一致，达到最终数据一致的目的
主从复制配置
主从复制配置步骤：
- 确保从数据库与主数据库里的数据一样
- 在主数据库里创建一个同步账号授权给从数据库使用
- 配置主数据库（修改配置文件）
- 配置从数据库（修改配置文件）
环境1说明：
| 数据库角色 | IP | 应用与系统版本 | 有无数据 |
|---|---|---|---|
| 主数据库master | 192.168.100.1 | redhat8 mariadb10.3.17 | 无数据 |
| 从数据库slave | 192.168.100.2 | redhat8 mariadb10.3.17 | 无数据 |
准备工作（安装mysql并且关闭防火墙）
[root@localhost ~]# yum -y install mariadb*
[root@localhost ~]# systemctl enable --now mariadb
[root@localhost ~]# systemctl stop firewalld
[root@localhost ~]# setenforce 0
在主数据库里创建一个同步账号授权给从数据库使用
master:
[root@master ~]# mysql
MariaDB [(none)]> grant replication slave on *.* to 'yqh'@'192.168.100.2' identified by '123456';
Query OK, 0 rows affected (0.003 sec)
MariaDB [(none)]> flush privileges;
Query OK, 0 rows affected (0.002 sec)
slave:
//测试连接
[root@slave ~]# mysql -uyqh -p123456 -h192.168.100.1
Welcome to the MariaDB monitor. Commands end with ; or g.
Your MariaDB connection id is 10
Server version: 10.3.17-MariaDB MariaDB Server
Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.
Type 'help;' or 'h' for help. Type 'c' to clear the current input statement.
MariaDB [(none)]>
配置主数据库
[root@master ~]# vim /etc/my.cnf
[mysqld]
log-bin = mysql_bin //启用binlog日志
server-id = 10 //数据库服务器唯一标识符，从库的server-id值必须比主库的大
[root@master ~]# systemctl restart mariadb
[root@master ~]# mysql
//查看主库的状态
MariaDB [(none)]> show master status;
+------------------+----------+--------------+------------------+
| File | Position | Binlog_Do_DB | Binlog_Ignore_DB |
+------------------+----------+--------------+------------------+
| mysql_bin.000001 | 328 | | |
+------------------+----------+--------------+------------------+
1 row in set (0.000 sec)
配置从数据库
[root@slave ~]# vim /etc/my.cnf
[mysqld]
relay-log = myrelay //启用中继日志relay-log
server-id = 20 //设置从库的唯一标识符，从库的server-id值必须大于主库的该值
[root@slave ~]# systemctl restart mariadb
//配置并启动主从复制
[root@slave ~]# mysql
MariaDB [(none)]> change master to master_host='192.168.100.1',master_user='yqh',master_password='123456',master_log_file='mysql_bin.000001',master_log_pos=328;
Query OK, 0 rows affected (0.008 sec)
MariaDB [(none)]> start slave;
Query OK, 0 rows affected (0.003 sec)
//查看从服务器状态
MariaDB [(none)]> show slave statusG
*************************** 1. row ***************************
Slave_IO_State: Waiting for master to send event
Master_Host: 192.168.100.1
Master_User: yqh
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: mysql_bin.000001
Read_Master_Log_Pos: 328
Relay_Log_File: myrelay.000002
Relay_Log_Pos: 555
Relay_Master_Log_File: mysql_bin.000001
Slave_IO_Running: Yes //此处必须为Yes
Slave_SQL_Running: Yes //此处必须为Yes
······
······
1 row in set (0.001 sec)
测试验证
在主服务器创建school数据库在创建student表并插入数据：
[root@master ~]# mysql
MariaDB [(none)]> create database school;
Query OK, 1 row affected (0.001 sec)
MariaDB [(none)]> use school
Database changed
MariaDB [school]> create table student(id int not null primary key auto_increment,name varchar(50),age tinyint,score float);
Query OK, 0 rows affected (0.008 sec)
MariaDB [school]> insert student(name,age,score) values('tom',20,100),('jerry',18,90),('zhangshan',23,97.5),('lisi',21,60.5);
Query OK, 4 rows affected (0.004 sec)
Records: 4 Duplicates: 0 Warnings: 0
MariaDB [school]> select * from student;
+----+-----------+------+-------+
| id | name | age | score |
+----+-----------+------+-------+
| 1 | tom | 20 | 100 |
| 2 | jerry | 18 | 90 |
| 3 | zhangshan | 23 | 97.5 |
| 4 | lisi | 21 | 60.5 |
+----+-----------+------+-------+
4 rows in set (0.001 sec)
在从数据库中查看数据是否同步：
[root@slave ~]# mysql
MariaDB [(none)]> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| school |
+--------------------+
4 rows in set (0.001 sec)
MariaDB [(none)]> use school;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A
Database changed
MariaDB [school]> show tables;
+------------------+
| Tables_in_school |
+------------------+
| student |
+------------------+
1 row in set (0.001 sec)
MariaDB [school]> select * from student;
+----+-----------+------+-------+
| id | name | age | score |
+----+-----------+------+-------+
| 1 | tom | 20 | 100 |
| 2 | jerry | 18 | 90 |
| 3 | zhangshan | 23 | 97.5 |
| 4 | lisi | 21 | 60.5 |
+----+-----------+------+-------+
4 rows in set (0.001 sec)
环境2说明：
| 数据库角色 | IP | 应用与系统版本 | 有无数据 |
|---|---|---|---|
| 主数据库master | 192.168.100.1 | redhat8 mariadb10.3.17 | 有数据 |
| 从数据库slave | 192.168.100.2 | redhat8 mariadb10.3.17 | 无数据 |
准备工作（安装mysql并且关闭防火墙）
[root@localhost ~]# yum -y install mariadb*
[root@localhost ~]# systemctl enable --now mariadb
[root@localhost ~]# systemctl stop firewalld
[root@localhost ~]# setenforce 0
模拟有数据的数据库：
[root@master ~]# mysql
MariaDB [(none)]> create database info;
Query OK, 1 row affected (0.001 sec)
MariaDB [(none)]> use info;
Database changed
MariaDB [info]> create table basic(id int not null primary key auto_increment,name varchar(50),job varchar(50));
Query OK, 0 rows affected (0.007 sec)
MariaDB [info]> insert basic (name,job) values ('tom','engineer'),('jerry','office');
Query OK, 2 row affected (0.002 sec)
MariaDB [info]> create table salary(name varchar(50),salary float);
Query OK, 0 rows affected (0.006 sec)
MariaDB [info]> insert salary values('tom',8000),('jerry',8500),('zhangshan',9000),('lisi',7500);
Query OK, 4 rows affected (0.001 sec)
Records: 4 Duplicates: 0 Warnings: 0
MariaDB [info]> show tables;
+----------------+
| Tables_in_info |
+----------------+
| basic |
| salary |
+----------------+
2 rows in set (0.001 sec)
MariaDB [info]> select * from basic;
+----+-------+----------+
| id | name | job |
+----+-------+----------+
| 1 | tom | engineer |
| 2 | jerry | office |
+----+-------+----------+
2 rows in set (0.001 sec)
MariaDB [info]> select * from salary;
+-----------+--------+
| name | salary |
+-----------+--------+
| tom | 8000 |
| jerry | 8500 |
| zhangshan | 9000 |
| lisi | 7500 |
+-----------+--------+
4 rows in set (0.001 sec)
确保从数据库与主数据库里的数据一样
为确保从数据库与主数据库里的数据一样，先全备主数据库并还原到从数据库中
//先查看主库有哪些库
[root@master ~]# mysql -uroot -e 'show databases;'
+--------------------+
| Database |
+--------------------+
| info |
| information_schema |
| mysql |
| performance_schema |
+--------------------+
//再查看从库有哪些库
[root@slave ~]# mysql -uroot -e 'show databases;'
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
+--------------------+
//全备主库
//全备主库时需要另开一个终端，给数据库加上读锁，避免在备份期间有其他人在写入导致数据不一致
MariaDB [(none)]> flush tables with read lock;
Query OK, 0 rows affected (0.001 sec)
//此锁表的终端必须在备份完成以后才能退出
MariaDB [(none)]> use info;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A
Database changed
MariaDB [info]> insert basic(name,job) values('zhangshan','teacher');
//无法写入数据
ERROR 1223 (HY000): Can't execute the query because you have a conflicting read lock
//另开一个终端：
[root@master ~]# mysqldump -uroot --all-databases > all.sql
[root@master ~]# ls
all.sql anaconda-ks.cfg
[root@master ~]# scp all.sql 192.168.100.2:/
root/
The authenticity of host '192.168.100.2 (192.168.100.2)' can't be established.
ECDSA key fingerprint is SHA256:yvB25r1iyD1DrH7KQlo2thy8nREkrS7Qddd1KQ5ucsQ.
Are you sure you want to continue connecting (yes/no/[fingerprint])? yes
Warning: Permanently added '192.168.100.2' (ECDSA) to the list of known hosts.
root@192.168.100.2's password:
all.sql 100% 469KB 27.3MB/s 00:00
//解除主库的锁表状态，直接退出交互式界面即可
mysql> quit
Bye
//在从库上恢复主库的备份并查看从库有哪些库，确保与主库一致
[root@slave ~]# mysql -uroot -e 'show databases;'
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
+--------------------+
[root@slave ~]# mysql < all.sql
[root@slave ~]# mysql -uroot -e 'show databases;'
+--------------------+
| Database |
+--------------------+
| info |
| information_schema |
| mysql |
| performance_schema |
+--------------------+
在主数据库里创建一个同步账号授权给从数据库使用
master:
[root@master ~]# mysql
MariaDB [(none)]> grant replication slave on *.* to 'yqh'@'192.168.100.2' identified by '123456';
Query OK, 0 rows affected (0.001 sec)
MariaDB [(none)]> flush privileges;
Query OK, 0 rows affected (0.001 sec)
slave:
//测试连接
[root@slave ~]# mysql -uyqh -p123456 -h192.168.100.1
Welcome to the MariaDB monitor. Commands end with ; or g.
Your MariaDB connection id is 10
Server version: 10.3.17-MariaDB MariaDB Server
Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.
Type 'help;' or 'h' for help. Type 'c' to clear the current input statement.
MariaDB [(none)]>
配置主数据库
[root@master ~]# vim /etc/my.cnf
[mysqld]
log-bin = mysql_bin //启用binlog日志
server-id = 10 //数据库服务器唯一标识符，从库的server-id值必须比主库的大
[root@master ~]# systemctl restart mariadb
[root@master ~]# mysql
//查看主库的状态
MariaDB [(none)]> show master status;
+------------------+----------+--------------+------------------+
| File | Position | Binlog_Do_DB | Binlog_Ignore_DB |
+------------------+----------+--------------+------------------+
| mysql_bin.000001 | 328 | | |
+------------------+----------+--------------+------------------+
1 row in set (0.000 sec)
配置从数据库
[root@slave ~]# vim /etc/my.cnf
[mysqld]
relay-log = myrelay //启用中继日志relay-log
server-id = 20 //设置从库的唯一标识符，从库的server-id值必须大于主库的该值
[root@slave ~]# systemctl restart mariadb
//配置并启动主从复制
[root@slave ~]# mysql
MariaDB [(none)]> change master to master_host='192.168.100.1',master_user='yqh',master_password='123456',master_log_file='mysql_bin.000001',master_log_pos=328;
Query OK, 0 rows affected (0.014 sec)
MariaDB [(none)]> start slave;
Query OK, 0 rows affected (0.002 sec)
//查看从服务器状态
MariaDB [(none)]> show slave statusG
*************************** 1. row ***************************
Slave_IO_State: Waiting for master to send event
Master_Host: 192.168.100.1
Master_User: yqh
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: mysql_bin.000001
Read_Master_Log_Pos: 328
Relay_Log_File: myrelay.000002
Relay_Log_Pos: 555
Relay_Master_Log_File: mysql_bin.000001
Slave_IO_Running: Yes
Slave_SQL_Running: Yes
······
······
1 row in set (0.001 sec)
测试验证
在从服务器上查看原有数据：
[root@slave ~]# mysql
MariaDB [(none)]> show databases;
+--------------------+
| Database |
+--------------------+
| info |
| information_schema |
| mysql |
| performance_schema |
+--------------------+
4 rows in set (0.001 sec)
MariaDB [(none)]> use info;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A
Database changed
MariaDB [info]> show tables;
+----------------+
| Tables_in_info |
+----------------+
| basic |
| salary |
+----------------+
2 rows in set (0.001 sec)
MariaDB [info]> select * from basic;
+----+-------+----------+
| id | name | job |
+----+-------+----------+
| 1 | tom | engineer |
| 2 | jerry | office |
+----+-------+----------+
2 rows in set (0.001 sec)
在主服务器上插入数据：
[root@master ~]# mysql
MariaDB [(none)]> use info;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A
Database changed
MariaDB [info]> insert basic(name,job) values('zhangshan','teacher');
Query OK, 1 row affected (0.002 sec)
在从数据库中查看数据是否同步：
[root@slave ~]# mysql
MariaDB [(none)]> use info;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A
Database changed
MariaDB [info]> select * from basic;
+----+-----------+----------+
| id | name | job |
+----+-----------+----------+
| 1 | tom | engineer |
| 2 | jerry | office |
| 3 | zhangshan | teacher |
+----+-----------+----------+
3 rows in set (0.001 sec)