MySQL主从

主从形式

 

 

原理：

（1）master服务器将数据的改变记录二进制binlog日志，当master上的数据发生改变时，则将其改变写入二进制日志中；

（2）slave服务器会在一定时间间隔内对master二进制日志进行探测其是否发生改变，如果发生改变，则开始一个I/OThread请求master二进制事件

（3）同时主节点为每个I/O线程启动一个dump线程，用于向其发送二进制事件，并保存至从节点本地的中继日志中，从节点将启动SQL线程从中继日志中读取二进制日志，在本地重放，使得其数据和主节点的保持一致。

 

主从复制配置

主从复制配置步骤：

1. 确保从数据库与主数据库里的数据一样
2. 在主数据库里创建一个同步账号授权给从数据库使用
3. 配置主数据库（修改配置文件）
4. 配置从数据库（修改配置文件

 搭建两台MySQL服务器，一台作为主服务器，一台作为从服务器，主服务器进行写操作，从服务器进行读操作

主数据库：IP192.168.248.130  无数据

从数据库：IP192.168.248.131  无数据

关闭主从防火墙和selinux

[root@slave ~]# systemctl stop firewalld
[root@slave ~]# setenforce 0

 查看主从数据库又那些库

#主库
[root@master ~]# mysql  -uroot -p123456 -e 'show databases;'
mysql: [Warning] Using a password on the command line interface can be insecure.
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
+--------------------+

#从库
[root@slave ~]# mysql -uroot -p123456 -e 'show databases;'
mysql: [Warning] Using a password on the command line interface can be insecure.
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
+--------------------+

在主数据库里创建一个同步账号授权给从数据库使用

#主库创建同步账号
mysql> grant replication  slave on *.* to 'test'@'192.168.248.131' identified by 'test123'；


#在从库登录测试
[root@slave ~]# mysql -utest -ptest123 -h192.168.248.130
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor.  Commands end with ; or g.
Your MySQL connection id is 4
Server version: 5.7.31-log MySQL Community Server (GPL)

Copyright (c) 2000, 2020, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or 'h' for help. Type 'c' to clear the current input statement.

mysql> 

配置主库数据库

#配置主库数据库
[root@master ~]vim /etc/my.cnf    
[mysqld]  #在mysqld下
...............
...............
server-id = 10  # 添加启用binlog日志
log-bin = mysql_bin  #添加据库服务器唯一标识符，主库的server-id值必须比从库的小
#重启mysql
[root@lmaster~]# service mysqld start
Starting MySQL. SUCCESS! 

#查看主库状态
mysql> show master status;
+------------------+----------+--------------+------------------+-------------------+
| File             | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set |
+------------------+----------+--------------+------------------+-------------------+
| mysql_bin.000001 |      451 |              |                  |                   |
+------------------+----------+--------------+------------------+-------------------+
1 row in set (0.01 sec)

配置从库数据库

#配置从库数据库
[root@slave ~]# vim /etc/my.cnf 
[mysqld]
............
............
server-id = 20
relay-log = mysql_relay_bin

#重启mysql
[root@slave ~]# service mysqld restart 
Shutting down MySQL.. SUCCESS! 
Starting MySQL.Logging to '/opt/data/slave.err'.
 SUCCESS!

#配置并启动主从复制
mysql> change master to
    -> master_host='192.168.248.130',
    -> master_user='test',
    -> master_password='test123',
    -> master_log_file='mysql_bin.000001',
    -> master_log_POS=451;
Query OK, 0 rows affected, 2 warnings (0.01 sec)

mysql> start  slave;
Query OK, 0 rows affected (0.00 sec)

#查看从服务器状态
mysql> show slave statusG
*************************** 1. row ***************************
               Slave_IO_State: Waiting for master to send event
                  Master_Host: 192.168.248.130
                  Master_User: test
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: mysql_bin.000001
          Read_Master_Log_Pos: 451
               Relay_Log_File: mysql_relay_bin.000002
                Relay_Log_Pos: 320
        Relay_Master_Log_File: mysql_bin.000001
             Slave_IO_Running: Yes    #看到两个yes表示成功  
            Slave_SQL_Running: Yes    

测试验证

在主库中写入数据

#在主库中创建表写入数据
mysql> create database t1;
Query OK, 1 row affected (0.01 sec)

mysql> use t1;
Database changed
mysql> create table test(id int not null auto_increment,name varchar(20),age tinyint,primary key(id));
Query OK, 0 rows affected (0.01 sec)

mysql> insert test(name,age) values('xx',34),('ww',24),('gg',25);
Query OK, 3 rows affected (0.01 sec)
Records: 3  Duplicates: 0  Warnings: 0

mysql> select * from test;
+----+------+------+
| id | name | age  |
+----+------+------+
|  1 | xx   |   34 |
|  2 | ww   |   24 |
|  3 | gg   |   25 |
+----+------+------+
3 rows in set (0.00 sec)

 在从库中查看数据是否同步

[root@slave ~]# mysql -uroot -p123456 -e 'select * from t1.test;'
mysql: [Warning] Using a password on the command line interface can be insecure.
+----+------+------+
| id | name | age  |
+----+------+------+
|  1 | xx   |   34 |
|  2 | ww   |   24 |
|  3 | gg   |   25 |
+----+------+------+

---

 搭建两台MySQL服务器，一台作为主服务器，一台作为从服务器，主服务器进行写操作，从服务器进行读操作

主数据库：IP192.168.248.130  有数据

从数据库：IP192.168.248.131  无数据

主库上有数据

[root@localhost ~]# mysql -uroot -p -e 'show databases;'
Enter password: 
+--------------------+
| Database           |
+--------------------+
| information_schema |
| jobs               |
| mysql              |
| performance_schema |
| sys                |
+--------------------+

[root@master ~]# mysql -uroot -p  -e 'select * from  jobs.student;'
Enter password: 
+----+---------+------+
| id | name    | age  |
+----+---------+------+
|  1 | alice   |   12 |
|  2 | natasha |   12 |
|  3 | harry   |   11 |
+----+---------+------+
 

 从库上无数据

[root@slave ~]# mysql -uroot -p -e 'show databases;'
Enter password: 
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
+--------------------+

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
mysql> FLUSH TABLES  WITH READ LOCK;
Query OK, 0 rows affected (0.01 sec

[root@master ~]# mysqldump -uroot -p123456 --all-databases > all_$(date +%F_%T).sql
mysqldump: [Warning] Using a password on the command line interface can be insecure.
[root@master ~]# ls
all_2021-01-02_18:34:26.sql

#将备份数据推送至从服务器
[root@master ~]# scp /root/all_2021-01-02_18:34:26.sql  'root'@192.168.248.131:/root/
root@192.168.248.131's password: 
all_2021-01-02_18:34:26.sql                                                  100%  843KB  87.2MB/s   00:00

#同步从库与主库，查看数据
[root@slave ~]# mysql -uroot -p  <all_2021-01-02_18:34:26.sql 
Enter password: 
[root@slave ~]# mysql -uroot -p -e 'show databases;'
Enter password: 
+--------------------+
| Database           |
+--------------------+
| information_schema |
| jobs               |
| mysql              |
| performance_schema |
| sys                |
+--------------------+
[root@slave ~]# mysql -uroot -p -e 'select * from jobs.student;'
Enter password: 
+----+---------+------+
| id | name    | age  |
+----+---------+------+
|  1 | alice   |   12 |
|  2 | natasha |   12 |
|  3 | harry   |   11 |
+----+---------+------+

#退出读锁终端

 后面就和主从无数据配置一样