第三天 运维高级 MySQL主从复制

1.理解MySQL主从复制原理

1、master（binlog dump thread）主要负责Master库中有数据更新的时候，会按照binlog格式，将更新的事件类型写入到主库的binlog文件中。

2、I/O thread线程在Slave中创建，该线程用于请求Master，Master会返回binlog的名称以及当前数据更新的位置、binlog文件位置的副本。将binlog保存在 「relay log（中继日志）」 中

3、SQL线程也是在Slave中创建的，当Slave检测到中继日志有更新，就会将更新的内容同步到Slave数据库中，这样就保证了主从的数据的同步

2.完成MySQL主从复制

环境准备
两台机器一主一从
由于服务器是克隆复制的，要更改从库的uuid

[root@localhost ~]# vim /var/lib/mysql/auto.cnf

[auto]
server-uuid=892dc96a-1b13-11ee-b662-000c29aba114

1、设置主从库的server-id值并开启binlog参数（从可以不用开启binlog）

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

log_bin=mysql-bin
server-id=140 # 主从的server-id唯一

2、在主库上建立同步账号

mysql> grant replication slave on *.* to 'user'@'192.168.159.%' identified by '12345';
Query OK, 0 rows affected, 1 warning (0.00 sec)

3、 备份主库数据

[root@localhost ~]# mysql -uroot -p12345 -e 'show databases'
mysql: [Warning] Using a password on the command line interface can be insecure.
+--------------------+
| Database           |
+--------------------+
| information_schema |
| db                 |
| mysql              |
| performance_schema |
| school             |
| sys                |
+--------------------+

[root@localhost ~]# mysqldump -uroot -p -A -B |gzip > db.sql.gz
Enter password: 

4、主库备份数据上传到从库

[root@localhost ~]# scp db.sql.gz 192.168.159.141:/root/
[email protected]'s password: 
db.sql.gz                                                        100%  205KB  68.4MB/s   00:00 

5、还原从主库备份数据

[root@localhost ~]# zcat db.sql.gz | mysql -uroot -p12345
mysql: [Warning] Using a password on the command line interface can be insecure.
[root@localhost ~]# mysql -uroot -p12345 -e 'show databases'
mysql: [Warning] Using a password on the command line interface can be insecure.
+--------------------+
| Database           |
+--------------------+
| information_schema |
| db                 |
| mysql              |
| performance_schema |
| school             |
| sys                |
+--------------------+

6、查看主库状态

mysql> show master status;
+------------------+----------+--------------+------------------+-------------------+
| File             | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set |
+------------------+----------+--------------+------------------+-------------------+
| mysql-bin.000007 |      742 |              |                  |                   |
+------------------+----------+--------------+------------------+-------------------+
1 row in set (0.00 sec)

7、设定从主库同步

mysql> change master to
    -> MASTER_HOST='192.168.159.140',
    -> MASTER_PORT=3306,
    -> MASTER_USER='user',
    -> MASTER_PASSWORD='12345',
    -> MASTER_LOG_FILE='mysql-bin.000007',
    -> MASTER_LOG_POS=742;
Query OK, 0 rows affected, 2 warnings (0.00 sec)

8、重启数据库

[root@localhost ~]# systemctl restart mysqld

9、启动从库同步开关并检查状态

mysql> start slave;
Query OK, 0 rows affected, 1 warning (0.00 sec)
mysql> show slave status\G

当都为yes是即成功

测试

问题：

当IO为connecting时，是由于没有关闭防火墙。关闭防火墙即可。