MySQL主从的介绍与应用

大家好，欢迎来到IT知识分享网。

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

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

3. 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：

3.1 mysql安装（两台主机安装一致，下面只演示一台主机操作）

分别在主从两台服务器上安装mysql8.0.35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。

1.修改主机名 [root@localhost ~]# hostnamectl set-hostname master [root@localhost ~]# bash [root@master ~]#  [root@localhost ~]# hostnamectl set-hostname slave [root@localhost ~]# bash [root@slave ~]#  2.关闭防火墙 [root@master ~]# systemctl disable --now firewalld Removed "/etc/systemd/system/multi-user.target.wants/firewalld.service". Removed "/etc/systemd/system/dbus-org.fedoraproject.FirewallD1.service". [root@master ~]# vi /etc/selinux/config [root@master ~]# cat /etc/selinux/config|grep '^SELINUX' SELINUX=disabled SELINUXTYPE=targeted [root@master ~]# setenforce 0 [root@master ~]# getenforce Permissive [root@slave ~]# systemctl disable --now firewalld Removed "/etc/systemd/system/multi-user.target.wants/firewalld.service". Removed "/etc/systemd/system/dbus-org.fedoraproject.FirewallD1.service". [root@slave ~]# vi /etc/selinux/config [root@slave ~]# cat /etc/selinux/config|grep '^SELINUX' SELINUX=disabled SELINUXTYPE=targeted [root@slave ~]# setenforce 0 [root@slave ~]# getenforce Permissive 3.下载软件包 [root@master ~]# ls anaconda-ks.cfg mysql-8.0.35-linux-glibc2.28-x86_64.tar.xz 4.压缩软件包 [root@master ~]# tar xf mysql-8.0.35-linux-glibc2.28-x86_64.tar.xz -C /usr/local [root@master ~]# cd /usr/local [root@master local]# ls bin etc games include lib lib64 libexec mysql-8.0.35-linux-glibc2.28-x86_64 sbin share src [root@master local]# mv mysql-8.0.35-linux-glibc2.28-x86_64 mysql [root@master local]# ls bin etc games include lib lib64 libexec mysql sbin share src [root@master local]#  5.配置环境变量 [root@master local]# ls bin etc games include lib lib64 libexec mysql sbin share src [root@master local]# echo 'export PATH=/usr/local/mysql/bin:$PATH' > /etc/profile.d/mysql.sh [root@master local]# source /etc/profile.d/mysql.sh  6.做软连接 [root@master local]# ls bin etc games include lib lib64 libexec mysql sbin share src [root@master local]# ln -s /usr/local/mysql/include/ /usr/include/mysql 7.告知lib在哪 [root@master local]# vim /etc/ld.so.conf.d/mysql.conf [root@master local]# ldconfig -v 8.添加帮助文档 [root@master local]# ls bin etc games include lib lib64 libexec mysql sbin share src [root@master local]# vim /etc/man_db.conf  # MANDATORY_MANPATH /usr/man MANDATORY_MANPATH /usr/share/man MANDATORY_MANPATH /usr/local/share/man MANDATORY_MANPATH /usr/local/mysql/man #--------------------------------------------------------- 9.创建用户并修改/usr/local/mysql/的所有者和所属组为mysql [root@master ~]# useradd -r -M -s /sbin/nologin mysql [root@master ~]# id mysql uid=991(mysql) gid=991(mysql) groups=991(mysql) [root@master ~]# chown -R mysql.mysql /usr/local/mysql  [root@master ~]# ll -d /usr/local/mysql drwxr-xr-x. 9 mysql mysql 129 Dec 26 16:40 /usr/local/mysql 10.创建数据库存放数据的目录并修改属组 [root@master ~]# mkdir /opt/data [root@master ~]# chown -R mysql.mysql /opt/data [root@master ~]# ll -d /opt/data drwxr-xr-x. 2 mysql mysql 6 Dec 26 16:48 /opt/data 11.初始化 [root@master ~]# mysqld --initialize --user mysql --datadir /opt/data 2023-12-26T08:49:43.Z 0 [System] [MY-013169] [Server] /usr/local/mysql/bin/mysqld (mysqld 8.0.35) initializing of server in progress as process 57766 2023-12-26T08:49:43.Z 1 [System] [MY-013576] [InnoDB] InnoDB initialization has started. 2023-12-26T08:49:43.Z 1 [System] [MY-013577] [InnoDB] InnoDB initialization has ended. 2023-12-26T08:49:45.083767Z 6 [Note] [MY-010454] [Server] A temporary password is generated for root@localhost: otVyge;=q7eY [root@master ~]# echo 'otVyge;=q7eY' > pass [root@master ~]# cat pass otVyge;=q7eY 12.向配置文件添加内容 [root@master ~]# vim /etc/my.cnf [root@master ~]# cat /etc/my.cnf [mysqld] basedir = /usr/local/mysql datadir = /opt/data port = 3306 socket = /tmp/mysql.sock pid-file = /opt/data/mysql.pid user = mysql skip-name-resolve 13.给mysql服务指定位置 [root@master ~]# cd /usr/local/mysql [root@master mysql]# ls bin docs include lib LICENSE man README share support-files [root@master mysql]# cd support-files/ [root@master support-files]# ls mysqld_multi.server mysql-log-rotate mysql.server [root@master support-files]# vim mysql.server  [root@master support-files]# cat mysql.server | grep '^datadir' datadir=/opt/data datadir_set= [root@master support-files]# cat mysql.server | grep '^basedir' basedir=/usr/local/mysql [root@master support-files]# systemctl daemon-reload 14.启动服务 [root@master support-files]# service mysqld start Starting MySQL.Logging to '/opt/data/master.err'. SUCCESS! [root@master support-files]# ss -antl State Recv-Q Send-Q Local Address:Port Peer Address:Port Process LISTEN 0 128 0.0.0.0:22 0.0.0.0:* LISTEN 0 70 *:33060 *:* LISTEN 0 151 *:3306 *:* LISTEN 0 128 [::]:22 [::]:* 15.设置开机自启 [root@master ~]# cd /usr/lib/systemd/system [root@master system]# cp sshd.service mysql.service [root@master system]# vim mysql.service [root@master system]# cat mysql.service  [Unit] Description=mysql server daemon After=network.target sshd-keygen.target [Service] Type=forking ExecStart=service mysqld start ExecStop=service mysqld stop ExecReload=/bin/kill -HUP $MAINPID [Install] WantedBy=multi-user.target [root@master system]# service mysqld stop Shutting down MySQL.ss. SUCCESS! [root@master system]# systemctl daemon-reload [root@master system]# systemctl status mysql ○ mysql.service - mysql server daemon Loaded: loaded (/usr/lib/systemd/system/mysql.service; disabled; preset: disabled) Active: inactive (dead) [root@master system]# systemctl enable --now mysql Created symlink /etc/systemd/system/multi-user.target.wants/mysql.service → /usr/lib/systemd/system/mysql.service. [root@master system]# systemctl status mysql ● mysql.service - mysql server daemon Loaded: loaded (/usr/lib/systemd/system/mysql.service; enabled; preset: disabled) Active: active (running) since Tue 2023-12-26 17:06:55 CST; 7s ago Process: 99845 ExecStart=service mysqld start (code=exited, status=0/SUCCESS) Main PID: 99862 (mysqld_safe) Tasks: 39 (limit: 10820) Memory: 371.5M CPU: 829ms CGroup: /system.slice/mysql.service ├─ 99862 /bin/sh /usr/local/mysql/bin/mysqld_safe --datadir=/opt/data --pid-file=/opt/data/mysql.pid └─ /usr/local/mysql/bin/mysqld --basedir=/usr/local/mysql --datadir=/opt/data --plugin-dir=/usr/local/mysql/lib/plugin --user=mysql --log-error=ma> Dec 26 17:06:53 master systemd[1]: Starting mysql server daemon... Dec 26 17:06:55 master service[99849]: Starting MySQL. SUCCESS! Dec 26 17:06:55 master systemd[1]: Started mysql server daemon. 16.修改数据库密码 [root@master ~]# cat pass otVyge;=q7eY [root@master ~]# mysql -uroot -p'otVyge;=q7eY' 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 8 Server version: 8.0.35 Copyright (c) 2000, 2023, Oracle and/or its affiliates. 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> alter user root@localhost identified with mysql_native_password by 'Passw0rd@_~'; Query OK, 0 rows affected (0.00 sec) mysql> quit Bye [root@master ~]# mysql -uroot -p'Passw0rd@_~' 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 11 Server version: 8.0.35 MySQL Community Server - GPL Copyright (c) 2000, 2023, Oracle and/or its affiliates. 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> show databases; +--------------------+ | Database | +--------------------+ | information_schema | | mysql | | performance_schema | | sys | +--------------------+ 4 rows in set (0.01 sec) 

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 | +--------------------+ 4 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) 

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

[root@master ~]# mysql -uroot -pPassw0rd@_~ 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 12 Server version: 8.0.35 MySQL Community Server - GPL Copyright (c) 2000, 2023, Oracle and/or its affiliates. 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> create user repl@192.168.116.143 identified with mysql_native_password by 'Passw0rd@_~'; Query OK, 0 rows affected (0.01 sec) mysql> grant replication slave on *.* to repl@192.168.116.143 -> ; Query OK, 0 rows affected (0.00 sec) mysql> flush privileges -> ; Query OK, 0 rows affected (0.01 sec) //到slave主机登入 [root@slave ~]# mysql -urepl -pPassw0rd@_~ -h192.168.116.140 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 11 Server version: 8.0.35 MySQL Community Server - GPL Copyright (c) 2000, 2023, Oracle and/or its affiliates. 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> 

3.2.3 配置主数据库

[root@master ~]# vim /etc/my.cnf [root@master ~]# cat /etc/my.cnf [mysqld] basedir = /usr/local/mysql datadir = /opt/data port = 3306 socket = /tmp/mysql.sock pid-file = /opt/data/mysql.pid user = mysql skip-name-resolve log-bin = mysql_bin server-id = 10 [root@master ~]# systemctl restart mysql [root@master ~]# ss -antl State Recv-Q Send-Q Local Address:Port Peer Address:Port Process LISTEN 0 128 0.0.0.0:22 0.0.0.0:* LISTEN 0 70 *:33060 *:* LISTEN 0 151 *:3306 *:* LISTEN 0 128 [::]:22 [::]:* //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 | 157 | | | | +------------------+----------+--------------+------------------+-------------------+ 1 row in set (0.00 sec) 

3.2.4 配置从数据库

[root@slave ~]# vim /etc/my.cnf [root@slave ~]# cat /etc/my.cnf [mysqld] basedir = /usr/local/mysql datadir = /opt/data port = 3306 socket = /tmp/mysql.sock pid-file = /opt/data/mysql.pid user = mysql skip-name-resolve relay-log = mysql_relay_bin server-id = 20 [root@slave ~]# systemctl restart mysql [root@slave ~]# ss -antl State Recv-Q Send-Q Local Address:Port Peer Address:Port Process LISTEN 0 128 0.0.0.0:22 0.0.0.0:* LISTEN 0 128 [::]:22 [::]:* LISTEN 0 151 *:3306 *:* LISTEN 0 70 *:33060 *:* //配置并启动主从复制 mysql> change master to -> master_host='192.168.116.140', -> master_user='repl', -> master_password='Passw0rd@_~', -> master_port=3306, -> master_log_file='mysql_bin.000001', -> master_log_pos=157; Query OK, 0 rows affected, 9 warnings (0.02 sec) mysql> start slave -> ; Query OK, 0 rows affected, 1 warning (0.01 sec) //查看从服务器状态 mysql> show slave status\G * 1. row * Slave_IO_State: Waiting for source to send event Master_Host: 192.168.116.140 Master_User: repl Master_Port: 3306 Connect_Retry: 60 Master_Log_File: mysql_bin.000001 Read_Master_Log_Pos: 157 Relay_Log_File: mysql_relay_bin.000002 Relay_Log_Pos: 326 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: 157 Relay_Log_Space: 536 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: 0 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: 10 Master_UUID: b6998aa8-a3cb-11ee-900f-000c29ed2b10 Master_Info_File: mysql.slave_master_info SQL_Delay: 0 SQL_Remaining_Delay: NULL Slave_SQL_Running_State: Replica has read all relay log; waiting for more updates 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: Master_public_key_path: Get_master_public_key: 0 Network_Namespace: 1 row in set, 1 warning (0.00 sec) 

3.2.5 测试验证

在主服务器创建库并创建表，向表中插入数据：

mysql> show databases; +--------------------+ | Database | +--------------------+ | information_schema | | mysql | | performance_schema | | sys | +--------------------+ 4 rows in set (0.01 sec) mysql> create database student; Query OK, 1 row affected (0.01 sec) mysql> use student; Database changed mysql> create table hl(id int not null,name varchar(20)); Query OK, 0 rows affected (0.02 sec) mysql> desc hl; +-------+-------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +-------+-------------+------+-----+---------+-------+ | id | int | NO | | NULL | | | name | varchar(20) | YES | | NULL | | +-------+-------------+------+-----+---------+-------+ 2 rows in set (0.01 sec) mysql> insert hl(id,name) value(1,'tom'),(2,'jerry'); Query OK, 2 rows affected (0.00 sec) Records: 2 Duplicates: 0 Warnings: 0 mysql> select * from hl; +----+-------+ | id | name | +----+-------+ | 1 | tom | | 2 | jerry | +----+-------+ 2 rows in set (0.00 sec) 

在从数据库中查看数据是否同步：

mysql> show databases; +--------------------+ | Database | +--------------------+ | information_schema | | mysql | | performance_schema | | student | | sys | +--------------------+ 5 rows in set (0.01 sec) mysql> select * from student.hl; +----+-------+ | id | name | +----+-------+ | 1 | tom | | 2 | jerry | +----+-------+ 2 rows in set (0.00 sec)