mysql主从
1. 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(备份的实例，服务器）
1.2 主从形式
- 一主一从：主出问题，从顶上。
- 主主复制：其中一个主工作，另外一个不会工作，两个的数据都会挂载到某一个共享存储上。
- 一主多从---扩展系统读取的性能，因为读是在从库读取的：一个主负责写，多个从负责读。一般用于写少读多。
- 多主一从---5.7开始支持：这一个从里面包括了多个主的数据。一般用于写多读少。
- 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
3. 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 | centos8/redhat8 mysql-5.7 |
有数据 |
| 从数据库 | 172.16.12.129 | centos8/redhat8 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，若有疑问请参考《mysql基础》与《mysql进阶》两篇文章。
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 [root@localhost ~]# mysql -uroot -pwangqing123! -e 'show databases;' mysql: [Warning] Using a password on the command line interface can be insecure. +--------------------+ | Database | +--------------------+ | information_schema | | mysql | | performance_schema | | student | | sys | | teacher | +--------------------+ //再查看从库有哪些库 [root@localhost ~]# mysql -uroot -pwangqing123! -e 'show databases;' mysql: [Warning] Using a password on the command line interface can be insecure. +--------------------+ | 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 (0.00 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@localhost ~]# mysqldump -uroot -pwangqing123! --all-databases > /opt/all-201808191200.sql mysqldump: [Warning] Using a password on the command line interface can be insecure. [root@localhost ~]# ls /opt/ all-201808191200.sql [root@localhost ~]# scp /opt/all-201808191200.sql root@172.16.12.129:/opt/ root@172.16.12.129's password: all-201808191200.sql 100% 786KB 10.6MB/s 00:00 //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@localhost ~]# mysql -uroot -pwangqing123! < /opt/all-201808191200.sql mysql: [Warning] Using a password on the command line interface can be insecure. [root@localhost ~]# mysql -uroot -pwangqing123! -e 'show databases;' mysql: [Warning] Using a password on the command line interface can be insecure. +--------------------+ | Database | +--------------------+ | information_schema | | mysql | | performance_schema | | student | | sys | | teacher | +--------------------+
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> grant replication slave on *.* to 'repl'@'192.168.6.134' identified by 'repl123!'; # 创建一个repl数据库用户，密码是repl123！赋予权限 mysql> flush privileges; # 刷新授权表 Query OK, 0 rows affected (0.00 sec)
3.2.3 配置主数据库
[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 sql-mode = STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION server-id=10 #启用binlog日志 log-bin=mysql_bin #数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服务 [root@localhost ~]# systemctl restart mysqld # 重启 [root@localhost ~]# systemctl status mysqld #查看状态 ● mysqld.service - mysql server daemon Loaded: loaded (/usr/lib/systemd/system/mysqld.service; enabled; > Active: active (running) since Mon 2022-07-04 04:09:23 CST; 22s a> Process: 1857 ExecStop=/usr/local/mysql/support-files/mysqld stop > Process: 1889 ExecStart=/usr/local/mysql/support-files/mysqld star> Main PID: 1902 (mysqld_safe) Tasks: 28 (limit: 23485) Memory: 183.0M CGroup: /system.slice/mysqld.service ├─1902 /bin/sh /usr/local/mysql/bin/mysqld_safe --datadir> └─2130 /usr/local/mysql/bin/mysqld --basedir=/usr/local/m> 7月 04 04:09:22 localhost.localdomain systemd[1]: Starting mysql ser> 7月 04 04:09:23 localhost.localdomain mysqld[1889]: Starting MySQL. > 7月 04 04:09:23 localhost.localdomain systemd[1]: Started mysql serv> lines 1-15/15 (END)
//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
[root@localhost ~]# vi /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 sql-mode = STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION server-id = 20 # 从库的server-id值必须大于主库的该值 relay-log = myrelay # 启用中继日志relay-log
#重启从库的mysql服务 [root@localhost ~]# systemctl restart mysqld [root@localhost ~]# systemctl status mysqld ● mysqld.service - mysql server daemon Loaded: loaded (/usr/lib/systemd/system/mysqld.service; enabled; > Active: active (running) since Sun 2022-07-03 20:22:00 CST; 3s ago Process: 1842 ExecStop=/usr/local/mysql/support-files/mysqld stop > Process: 1874 ExecStart=/usr/local/mysql/support-files/mysqld star> Main PID: 1889 (mysqld_safe) Tasks: 28 (limit: 23485) Memory: 180.4M CGroup: /system.slice/mysqld.service ├─1889 /bin/sh /usr/local/mysql/bin/mysqld_safe --datadir> └─2115 /usr/local/mysql/bin/mysqld --basedir=/usr/local/m> 7月 03 20:21:59 localhost.localdomain systemd[1]: Starting mysql ser> 7月 03 20:22:00 localhost.localdomain mysqld[1874]: Starting MySQL. > 7月 03 20:22:00 localhost.localdomain systemd[1]: Started mysql serv> lines 1-15/15 (END)
#配置并启动主从复制，从库配置 mysql> change master to # 主是 -> master_host='192.168.6.133', # 主的ip -> master_user='repl', # 主的用户名字 -> master_password='repl123!', # 用户的密码 -> master_log_file='mysql_bin.000001', #放数据的二进制文件名字 -> master_log_pos=154; # 记录的位子 Query OK, 0 rows affected, 2 warnings (0.00 sec) mysql> start slave; # 配置完成启动主从 Query OK, 0 rows affected (0.00 sec) mysql> show slave status \G # 查看服务器状态 *************************** 1. row *************************** Slave_IO_State: Waiting for master to send event Master_Host: 192.168.6.133 Master_User: repl Master_Port: 3306 Connect_Retry: 60 Master_Log_File: mysql_bin.000001 Read_Master_Log_Pos: 154 Relay_Log_File: myrelay.000002 Relay_Log_Pos: 320 Relay_Master_Log_File: mysql_bin.000001 Slave_IO_Running: Yes # 要IO进程和SQL进程都是yes Slave_SQL_Running: Yes
验证
# 主数据库里操作 mysql> show databases; #创建一个school库 +--------------------+ | Database | +--------------------+ | information_schema | | mysql | | performance_schema | | sys | +--------------------+ 4 rows in set (0.00 sec) mysql> create database school; Query OK, 1 row affected (0.01 sec) mysql> show databases; # 查看 +--------------------+ | Database | +--------------------+ | information_schema | | mysql | | performance_schema | | school | | sys | +--------------------+ 5 rows in set (0.00 sec)
从库查看
mysql> show databases; # 有school库 +--------------------+ | Database | +--------------------+ | information_schema | | mysql | | performance_schema | | school | | sys | +--------------------+ 5 rows in set (0.00 sec)
主库操作
mysql> create table sym(id int primary key auto_increment,name varchar # 创建sym表 Query OK, 0 rows affected (0.01 sec) mysql> show tables; +------------------+ | Tables_in_school | +------------------+ | sym | +------------------+ 1 row in set (0.00 sec)
从库
mysql> use school; 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> show tables; +------------------+ | Tables_in_school | +------------------+ | sym | +------------------+ 1 row in set (0.00 sec) # 主库创建的从库也可以查看到
主库操作
mysql> insert into sym (id,name) values(1,'zhangsan'),(2,'lisi'),(3,'wangwu'),(4,'zhaoliu'); #往表里添加数据 Query OK, 4 rows affected (0.00 sec) Records: 4 Duplicates: 0 Warnings: 0 mysql> select * from sym; # 查看 +----+----------+ | id | name | +----+----------+ | 1 | zhangsan | | 2 | lisi | | 3 | wangwu | | 4 | zhaoliu | +----+----------+ 4 rows in set (0.00 sec)
从库查看
mysql> select * from sym; +----+----------+ | id | name | +----+----------+ | 1 | zhangsan | | 2 | lisi | | 3 | wangwu | | 4 | zhaoliu | +----+----------+ 4 rows in set (0.00 sec) #从库查看
