1.主從簡介

1.1誕生原因

資料庫隱患：訪問人多，伺服器宕機
伺服器時間長質量問題資料丟失

1.2主從作用

• 實時災備，用於故障切換
• 讀寫分離，提供查詢服務
• 備份，避免影響業務

1.3形式

• 1主1從
• 主主複製（高可用）
• 1主多從
• 多主1從（5.7版本支援）
• 聯級複製

2.主從原理

• 使用者在主機寫入（增刪改），資料庫改變，二進位制日誌記錄生成日誌備份（logdump）執行緒。從機的I/O執行緒請求讀取，主機收到請求後傳輸給從機。從機寫入中繼日誌（relaylog），從機的SQL執行緒讀取中繼日誌，解析後重現主機的操作

3.主從複製配置

環境

3.1建立同步使用者

• 看主表有的庫

mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| school             |
| sys                |
+--------------------+
5 rows in set (0.00 sec)

 

• 看從表有的庫

mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
+--------------------+
4 rows in set (0.00 sec)

• 主從關掉防火牆selinux

[root@matster ~]# systemctl stop firewalld.service 
[root@matster ~]# setenforce 0

 

• 全備主庫

備份前上讀鎖
MariaDB [(none)]> flush tables with read lock;
Query OK, 0 rows affected (0.001 sec)
//全備
[root@localhost ~]# mysqldump -uroot -p123456 --all-databases>all-20210104.sql
[root@localhost ~]# ll
total 476
-rw-r--r--  1 root root 482035 Jan  4 10:38 all-20210104.sql
-rw-------. 1 root root   1179 Jan  4 00:36 anaconda-ks.cfg
//將資料傳給從
[root@localhost ~]# scp /root/all-20210104.sql 'root'@'192.168.94.140':/root/
The authenticity of host '192.168.94.140 (192.168.94.140)' can't be established.
ECDSA key fingerprint is SHA256:3N9nRI4b+PknMMJ8yhtDWv/UjyjRNYizaOHP28glw0E.
Are you sure you want to continue connecting (yes/no/[fingerprint])? yes
Warning: Permanently added '192.168.94.140' (ECDSA) to the list of known hosts.
[email protected]'s password: 
all-20210104.sql                                                                   100%  471KB  68.1MB/s   00:00

• 同步主從資料

//從端恢復資料
[root@localhost ~]# mysql -uroot -p <all-20210104.sql 
Enter password: 
[root@localhost ~]# mysql -uroot -p123456 -e 'show databases;'
+--------------------+
| Database           |
+--------------------+
| company            |
| information_schema |
| mysql              |
| performance_schema |
| school             |
+--------------------+

• 建立主從同步使用者並授權（主上操作）

//建立使用者(主)
mysql> create user 'repl'@'192.168.94.140' IDENTIFIED BY 'repl123';
Query OK, 0 rows affected (0.00 sec)

//授權並重新整理
mysql> GRANT REPLICATION SLAVE ON *.* TO 'repl'@'192.168.94.140';
Query OK, 0 rows affected (0.00 sec)
mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)

• 連線測試(從連主)

[root@localhost ~]# mysql -urepl -prepl123 -h192.168.94.141
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 9
Server version: 5.7.31 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> 

3.2配置資料庫

• 配置主

[root@localhost ~]# vim /etc/my.cnf

[mysqld]
log-bin=mysql-bin   
server-id=10
[root@localhost ~]# systemctl restart mariadb.service 
//檢視
MariaDB [(none)]> show master status;
+------------------+----------+--------------+------------------+
| File             | Position | Binlog_Do_DB | Binlog_Ignore_DB |
+------------------+----------+--------------+------------------+
| mysql-bin.000001 |      328 |              |                  |
+------------------+----------+--------------+------------------+
1 row in set (0.000 sec)

• 配置從

[root@localhost ~]# vim /etc/my.cnf

[mysqld]
server-id=20
relay-log=mysql-relay-bin
//設定從
MariaDB [(none)]> change master to \
    -> master_host='192.168.94.141',\
    -> master_user='repl',\
    -> master_password='123456',\
    -> master_log_file='mysql-bin.000001',\
    -> master_log_pos=328;
Query OK, 0 rows affected (0.006 sec)

MariaDB [(none)]> start slave;
Query OK, 0 rows affected (0.001 sec)
//檢視狀態
MariaDB [(none)]> show slave status \G;
*************************** 1. row ***************************
                Slave_IO_State: Waiting for master to send event
                   Master_Host: 192.168.94.141
                   Master_User: repl
                   Master_Port: 3306
                 Connect_Retry: 60
               Master_Log_File: mysql-bin.000001
           Read_Master_Log_Pos: 328
                Relay_Log_File: mysql-relay-bin.000002
                 Relay_Log_Pos: 555
         Relay_Master_Log_File: mysql-bin.000001
              Slave_IO_Running: Yes
             Slave_SQL_Running: Yes

• 測試

//主增加記錄mia
MariaDB [school]> select * from school.student;
+----+-------------+------+
| id | name        | age  |
+----+-------------+------+
|  1 | tom         |   24 |
|  2 | jerry       |   23 |
|  3 | wangqing    |   25 |
|  4 | zhangshan   |   26 |
|  5 | zhangshan   |   20 |
|  6 | lisi        |   27 |
|  7 | cchenshuo   |   10 |
|  8 | wangwu      |    3 |
|  9 | qiuyi       |   15 |
| 10 | qiuxiaotian |   20 |
| 11 | eason       |   28 |
+----+-------------+------+
11 rows in set (0.000 sec)
MariaDB [school]> insert student(name,age) value('mia',24);
Query OK, 1 row affected (0.001 sec)

//從檢視
MariaDB [school]> select * from school.student;
+----+-------------+------+
| id | name        | age  |
+----+-------------+------+
|  1 | tom         |   24 |
|  2 | jerry       |   23 |
|  3 | wangqing    |   25 |
|  4 | zhangshan   |   26 |
|  5 | zhangshan   |   20 |
|  6 | lisi        |   27 |
|  7 | cchenshuo   |   10 |
|  8 | wangwu      |    3 |
|  9 | qiuyi       |   15 |
| 10 | qiuxiaotian |   20 |
| 11 | eason       |   28 |
| 12 | mia         |   24 |
+----+-------------+------+
12 rows in set (0.000 sec)