mysql主从
- 主从简介
在现代企业中，数据显得尤为重要，而存储数据的数据库选择又五花八门，但无论是何种数据库，均存在着一种隐患。
想几个问题：
用一台数据库存放数据，若此数据库服务器宕机了导致数据丢失怎么办？
业务量大了，数据多了，访问的人多了，一台数据库无法保证服务质量了怎么办？
1.1 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
1.2 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—5.7开始支持
联级复制
2. 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，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：
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）
需求：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
环境说明：
数据库角色 IP 应用与系统版本 有无数据
主数据库 192.168.110.10 centos7 mysql-5.7 有数据
从数据库 192.168.110.30 centos7 mysql-5.7 无数据
3.1 mysql安装
分别在主从两台服务器上安装mysql-5.7版本，此处略过安装步骤，步骤在前面几天已经讲解过
3.2 mysql主从配置
3.2.1 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
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| sys |
| ws |
+--------------------+
5 rows in set (0.00 sec)
//再查看从库有哪些库
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| sys |
+--------------------+
4 rows in set (0.00 sec)
//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)
//此锁表的终端必须在备份完成以后才能退出
//备份主库并将备份文件传送到从库
[root@ws ~]# mysqldump -uroot -p123456 --all-databases > all-databases-20250912.sql
mysqldump: [Warning] Using a password on the command line interface can be insecure.
[root@ws ~]# scp all-databases-20250912.sql @root 192.168.110.30:.
root@192.168.110.30's password:
all-databases-20250912.sql 100% 854KB 21.3MB/s 00:00
@root: No such file or directory
//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@ws3 ~]# mysql -uroot -p123456 < all-databases-20250912.sql
mysql: [Warning] Using a password on the command line interface can be insecure.
[root@ws3 ~]# 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 |
| ws |
+--------------------+
3.2.2 在主数据库里创建一个同步账号授权给从数据库使用
mysql> create user 'repl'@'192.168.100.30' identified by 'redhat';
Query OK, 0 rows affected (0.01 sec)
mysql> grant replication slave on *.* to 'repl'@'192.168.100.30';
Query OK, 0 rows affected (0.00 sec)
//replication slave:授予从库权限
//*.*: 授予从库的所有数据库的所有表权限
mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)
3.2.3 配置主数据库
[root@ws ~]# cat /etc/my.cnf
[mysqld]
basedir = /usr/local/mysql
datadir = /opt/data
socket = /tmp/mysql.sock
port = 3306
pid-file = /opt/data/mysql.pid
user = mysql
skip-name-resolve
server-id = 1 //主库设置为1，那么从库要设置的比1大
log-bin = mysql-bin
symbolic-links = 0 //软连接
log-error = /var/log/mysqld.log //错误日志
//重启mysql服务
[root@ws ~]# systemctl restart mysqld.service
[root@ws ~]# ss -antl
State Recv-Q Send-Q Local Address:Port Peer Address:Port
LISTEN 0 128 *:111 *:*
LISTEN 0 128 *:6000 *:*
LISTEN 0 5 192.168.122.1:53 *:*
LISTEN 0 128 *:22 *:*
LISTEN 0 128 127.0.0.1:631 *:*
LISTEN 0 100 127.0.0.1:25 *:*
LISTEN 0 128 127.0.0.1:6010 *:*
LISTEN 0 128 127.0.0.1:6011 *:*
LISTEN 0 128 127.0.0.1:6012 *:*
LISTEN 0 80 :::3306 :::*
LISTEN 0 128 :::111 :::*
LISTEN 0 128 :::80 :::*
LISTEN 0 128 :::6000 :::*
LISTEN 0 128 :::22 :::*
LISTEN 0 128 ::1:631 :::*
LISTEN 0 100 ::1:25 :::*
LISTEN 0 128 ::1:6010 :::*
LISTEN 0 128 ::1:6011 :::*
LISTEN 0 128 ::1:6012 :::*
//查看主库的状态
mysql> show master status;
+------------------+----------+--------------+------------------+-------------------+
| File | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set |
+------------------+----------+--------------+------------------+-------------------+
| mysql-bin.000001 | 154 | | | |
+------------------+----------+--------------+------------------+-------------------+
1 row in set (0.00 sec)
3.2.4 配置从数据库
[mysqld]
basedir = /usr/local/mysql
datadir = /opt/data
socket = /tmp/mysql.sock
port = 3306
pid-file = /opt/data/mysql.pid
user = mysql
skip-name-resolve
server-id = 2 //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
relay-log = mysql-relay-bin //启用中继日志relay-log
symbolic-links = 0
log-error = /var/log/mysqld.log
//重启从库的mysql服务
[root@ws3 ~]# systemctl restart mysqld
[root@ws3 ~]# ss -antl
State Recv-Q Send-Q Local Address:Port Peer Address:Port
LISTEN 0 128 *:111 *:*
LISTEN 0 128 *:6000 *:*
LISTEN 0 5 192.168.122.1:53 *:*
LISTEN 0 128 *:22 *:*
LISTEN 0 128 127.0.0.1:631 *:*
LISTEN 0 100 127.0.0.1:25 *:*
LISTEN 0 128 127.0.0.1:6010 *:*
LISTEN 0 80 :::3306 :::*
LISTEN 0 128 :::111 :::*
LISTEN 0 128 :::80 :::*
LISTEN 0 128 :::6000 :::*
LISTEN 0 128 :::22 :::*
LISTEN 0 128 ::1:631 :::*
LISTEN 0 100 ::1:25 :::*
LISTEN 0 128 ::1:6010 :::*
//配置并启动主从复制
mysql> change master to
-> master_host='192.168.110.10',
-> master_user='repl',
-> master_password='123456',
-> master_log_file='mysql-bin.000001',
-> master_log_pos=154;
Query OK, 0 rows affected, 2 warnings (0.02 sec)
mysql> start slave;
Query OK, 0 rows affected (0.00 sec)
//查看从服务器状态
mysql> show slave status\G
*************************** 1. row ***************************
Slave_IO_State:
Master_Host: 192.168.110.10
Master_User: repl
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: mysql-bin.000001
Read_Master_Log_Pos: 154
Relay_Log_File: mysql-relay-bin.000001
Relay_Log_Pos: 4
Relay_Master_Log_File: mysql-bin.000001
Slave_IO_Running: Yes
Slave_SQL_Running: Yes
Replicate_Do_DB:
Replicate_Ignore_DB:
Replicate_Do_Table:
Replicate_Ignore_Table:
Replicate_Wild_Do_Table:
Replicate_Wild_Ignore_Table:
Last_Errno: 0
Last_Error:
Skip_Counter: 0
Exec_Master_Log_Pos: 154
Relay_Log_Space: 154
Until_Condition: None
Until_Log_File:
Until_Log_Pos: 0
Master_SSL_Allowed: No
Master_SSL_CA_File:
Master_SSL_CA_Path:
Master_SSL_Cert:
Master_SSL_Cipher:
Master_SSL_Key:
Seconds_Behind_Master: NULL
Master_SSL_Verify_Server_Cert: No
Last_IO_Errno: 0
Last_IO_Error:
Last_SQL_Errno: 0
Last_SQL_Error:
Replicate_Ignore_Server_Ids:
Master_Server_Id: 0
Master_UUID:
Master_Info_File: /opt/data/master.info
SQL_Delay: 0
SQL_Remaining_Delay: NULL
Slave_SQL_Running_State:
Master_Retry_Count: 86400
Master_Bind:
Last_IO_Error_Timestamp:
Last_SQL_Error_Timestamp:
Master_SSL_Crl:
Master_SSL_Crlpath:
Retrieved_Gtid_Set:
Executed_Gtid_Set:
Auto_Position: 0
Replicate_Rewrite_DB:
Channel_Name:
Master_TLS_Version:
1 row in set (0.00 sec)
3.2.5 测试验证
在主库插入一组数据
mysql> select * from xs;
+------+-------+
| id | name |
+------+-------+
| 1 | bob |
| 2 | marry |
+------+-------+
2 rows in set (0.00 sec)
mysql> insert into xs value(3,'wangwu');
Query OK, 1 row affected (0.01 sec)
mysql> select * from xs;
+------+--------+
| id | name |
+------+--------+
| 1 | bob |
| 2 | marry |
| 3 | wangwu |
+------+--------+
3 rows in set (0.00 sec)
在从库查看
mysql> use ws;
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
mysql> select * from xs;
+------+--------+
| id | name |
+------+--------+
| 1 | bob |
| 2 | marry |
| 3 | wangwu |
+------+--------+
3 rows in set (0.00 sec)
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