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。
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---5.7开始支持
- 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,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)
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 | 172.16.12.128 | centos7/redhat7 mysql-5.7 |
有数据 |
从数据库 | 172.16.12.129 | centos7/redhat7 mysql-5.7 |
无数据 |
查看主从有什么库,准备两台虚拟机
[root@master ~]# mysql -uroot -p123 MariaDB [(none)]> show databases; +--------------------+ | Database | +--------------------+ | information_schema | | mysql | | performance_schema | +--------------------+ [root@slave ~]# mysql -uroot -p123 MariaDB [(none)]> show databases; +--------------------+ | Database | +--------------------+ | information_schema | | mysql | | performance_schema | +--------------------+ [root@master ~]# systemctl stop firewalld [root@master ~]# setenforce 0 [root@master ~]# mysql -uroot -p123 MariaDB [(none)]> grant replication cb2 on *.* to ‘cb‘@‘192.168.122.134‘ identified by ‘cb123‘; MariaDB [(none)]> flush privileges; [root@slave ~]# systemctl stop firewalld [root@slave ~]# setenforce 0 [root@slave ~]# mysql -ucb -pcb123 -h192.168.122.134
配置主数据库
[root@master ~]# vim /etc/my.cnf # This group is read both both by the client and the server # use it for options that affect everything # [client-server] [mysqld] log-bin=mysql_bin server-id=10 # # include all files from the config directory # !includedir /etc/my.cnf.d [root@master ~]# systemctl restart mariadb [root@master ~]# mysql -uroot -p123 MariaDB [(none)]> show master status; +------------------+----------+--------------+------------------+ | File | Position | Binlog_Do_DB | Binlog_Ignore_DB | +------------------+----------+--------------+------------------+ | mysql_bin.000001 | 432 | | | +------------------+----------+--------------+------------------+
配置从库数据
[root@slave ~]# vi /etc/my.cnf # # This group is read both both by the client and the server # use it for options that affect everything # [client-server] [mysqld] server-id=20 relay-log=myrelay # # include all files from the config directory !includedir /etc/my.cnf.d [root@slave ~]# systemctl restart mariadb [root@slave ~]# mysql -uroot -p123 MariaDB [(none)]> change master to master_host=‘192.168.122.134‘,master_user=‘cb‘,master_password=‘cb123‘,master_log_file=‘mysql_bin.000001‘,master_log_pos=432; MariaDB [(none)]> start slave; MariaDB [(none)]> show slave status\G Slave_IO_Running: Yes Slave_SQL_Running: Yes
测试验证
mysql> create database cb; Query OK, 1 row affected (0.02 sec) mysql> use cb; 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(‘aa‘,21),(‘bb‘,22),(‘cc‘,23); Query OK, 3 rows affected (0.01 sec) Records: 3 Duplicates: 0 Warnings: 0 mysql> select * from test; +----+------+------+ | id | name | age | +----+------+------+ | 1 | aa | 21 | | 2 | bb | 22 | | 3 | cc | 23 | +----+------+------+ 3 rows in set (0.01 sec)
在从库中查看数据是否同步
[root@slave ~]# mysql -ucb -pcb123 -e ‘select * from cb.test;‘ mysql: [Warning] Using a password on the command line interface can be insecure. +----+------+------+ | id | name | age | +----+------+------+ | 1 | aa | 21 | | 2 | bb | 22 | | 3 | cc | 23 | +----+------+------+
数据库角色 | IP | 有无数据 |
---|---|---|
主数据库 | 192.168.122.134 | 有数据 |
从数据库 | 192.168.122.130 | 无数据 |
主库
[root@localhost ~]# mysql -uroot -p -e ‘show databases;‘ Enter password: +--------------------+ | Database | +--------------------+ | information_schema | | cb | | mysql | | performance_schema | +--------------------+ [root@master ~]# mysql -uroot -p -e ‘select * from cb.student;‘ Enter password: +----+---------+------+ | id | name | age | +----+---------+------+ | 1 | tom | 11 | | 2 | zhangshan | 12 | | 3 | lisi | 13 | +----+---------+------+
从库
[root@slave ~]# mysql -uroot -p -e ‘show databases;‘ Enter password: +--------------------+ | Database | +--------------------+ | information_schema | | mysql | | performance_schema | +--------------------+
全备主库
MariaDB [(none)]> flush tables with read lock; Query OK, 0 rows affected (0.02 sec [root@master ~]# mysqldump -uroot -p123 --all-databases >all.sql mysqldump: [Warning] Using a password on the command line interface can be insecure. [root@master ~]# scp all.sql 192.168.122.134:/root [root@slave ~]# mysql -uroot -p123 < all.sql [root@slave ~]# mysql -uroot -p123 -e ‘show databases;‘ +--------------------+ | Database | +--------------------+ | cb | | information_schema | | mysql | | performance_schema | +--------------------+