1. 主从原理1.1 主从介绍
所谓 mysql 主从就是建立两个完全一样的数据库，其中一个为主要使用的数据库，另一个为次要的数据库，一般在企业中，存放比较重要的数据的数据库服务器需要配置主从，这样可以防止因数据库服务器宕机导致数据丢失，还能保证业务量太多、数据太多和访问人数太多时服务的质量（服务器响应速度），还能提供故障切换、读写分离、和备份等等功能
1.2 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
1.3 主从形式
一主一从
主主复制：当作备份使用，当主服务器出现故障时，另一个主服务器会自动顶上。
一主多从：用来实现读写分离，当写操作较少时，读操作较多时使用，主服务器用来实现写操作，从服务器用来实现读操作。
多主一从：用来实现读写分离，当写操作较多时，读操作较少时使用，主服务器用来实现写操作，从服务器用来实现读操作。5.7 开始支持
联级复制：是指从主场地复制过来的又从该场地再次复制到其他场地，即 A 场地把数据复制到 B 场地，B 场地又把这些数据或其中部分数据再复制到其他场地。
1.4 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
2. 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192.168.23.4Centos7.8 mysql-5.7有数据从数据库192.168.23.5Centos7.8 mysql-5.7无数据2.1Mysql安装
注意：需把安装包分别上传到两台服务器上分别执行下列命令进行安装
[root@localhost soft]# yum remove mysql-libs[root@localhost soft]# rpm -qa | grep mariadb进行安装
将下载好的mysql-5.7.22-1.el7.x86_64.rpm-bundle.tar上传
安装相应软件[root@localhost soft]# yum install -y openssl-devel.x86_64 openssl.x86_64 yum install -y libaio.x86_64 libaio-devel.x86_64 yum install -y perl.x86_64 perl-devel.x86_64 yum install -y perl-JSON.noarch yum install -y autoconf yum install -y wget yum install -y net-tools关闭防火墙[root@localhost soft]# systemctl stop firewalld[root@localhost soft]# systemctl disable firewalld解压软件包：[root@localhost soft]# tar -xvf mysql-5.7.22-1.el7.x86_64.rpm-bundle.tar
[root@localhost soft]# rpm -ivh mysql-community-common-5.7.22-1.el7.x86_64.rpm[root@localhost soft]# rpm -ivh mysql-community-libs-5.7.22-1.el7.x86_64.rpm[root@localhost soft]# rpm -ivh mysql-community-client-5.7.22-1.el7.x86_64.rpm[root@localhost soft]# rpm -ivh mysql-community-server-5.7.22-1.el7.x86_64.rpm[root@localhost soft]# rpm -ivh mysql-community-libs-compat-5.7.22-1.el7.x86_64.rpm[root@localhostsoft]#rpm -ivh mysql-community-embedded-compat-5.7.22-1.el7.x86_64.rpm[root@localhost soft]# rpm -ivh mysql-community-devel-5.7.22-1.el7.x86_64.rpm[root@localhost soft]# rpm -ivh mysql-community-test-5.7.22-1.el7.x86_64.rpm查看安装版本：[root@localhost soft]# mysql -V
编辑配置文件
vim /etc/my.cnf
#跳过登录验证 无需密码即可登录mysql
skip-grant-tables
# 设置默认字符集UTF-8
character_set_server=utf8
collation-server=utf8_general_ci
# 设置默认字符集UTF-8
init_connect=’SET NAMES utf8′
# 设置数据库日志过期天数为14天
server_id=1
expire_logs_days=14
[client]
default-character-set=utf8
##添加skip-grant-tablescharacter_set_server=utf8collation-server=utf8_general_ciinit_connect='SET NAMES utf8'server_id=1expire_logs_days=14[client]default-character-set=utf8
启动mysql[root@localhost soft]# systemctl start mysqld.service[root@localhost soft]# systemctl status mysqld
获取mysql的root用户的初始密码[root@localhost soft]# grep 'temporary password' /var/log/mysqld.log
以获取mysql的root用户的初始密码登录数据库[root@localhost soft]# mysql -u root -pAcqWlI64o:kG
修改root密码mysql> flush privileges;mysql> set password for root@localhost=password('123456');使密码即时生效mysql> flush privileges;允许以root身份远程登录mysqlmysql> grant all privileges on *.* to root@'%' identified by "123456";mysql> flush privileges;2.2 mysql 主从配置
2.2.1 确保从数据库于主数据库的数据一样
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
//主库为master[root@localhost ~]# hostnamectl set-hostname master[root@localhost ~]# bash[root@master ~]# 
//从库为slave[root@localhost ~]# hostnamectl set-hostname slave[root@localhost ~]# bash[root@slave ~]# 
//先查看主库有哪些库[root@master soft]# 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 || test |+--------------------+//在查看从库[root@slave soft]# 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 |+--------------------+//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@master soft]# mysqldump -uroot -p123456 --all-databases > /opt/acc-2022.sql;mysqldump: [Warning] Using a password on the command line interface can be insecure.[root@master ~]# ls /opt/
[root@master soft]# scp /opt/acc-2022.sql root@192.168.23.5:/opt/ 
//解除主库的锁表状态，直接退出交互式界面即可 mysql> quitBye[root@master ~]# //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@slave ~]# mysql -uroot -p123456 < /opt/acc-2022.sqlmysql: [Warning] Using a password on the command line interface can be insecure.[root@slave ~]# 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 || test |+--------------------+[root@slave ~]#
2.2.3 配置主数据库
[root@master soft]# vim /etc/my.cnf//在[mysql]这段后面添加datadir=/var/lib/mysqlsocket=/var/lib/mysql/mysql.sock log-bin=mysql-bin //添加 启用binlog日志server-id=1 //添加 数据库服务器唯一标识符，主库的server-id值必须比从库的小# Disabling symbolic-links is recommended to prevent assorted security risks symbolic-links=0 log-error=/var/log/mysqld.log pid-file=/var/run/mysqld/mysqld.pid 
//重启数主库的mysql服务[root@master soft]# systemctl restart mysqld[root@master soft]# ss -anltState Recv-Q Send-Q Local Address:Port Peer Address:PortLISTEN 0 128 *:22 *:*LISTEN 0 128 [::]:22 [::]:*LISTEN 0 80 [::]:3306 [::]:*[root@master soft]#//查看主库状态[root@master soft]# mysql -uroot -p123456mysql: [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 2Server version: 5.7.22-log MySQL Community Server (GPL)Copyright (c) 2000, 2018, Oracle and/or its affiliates. All rights reserved.Oracle is a registered trademark of Oracle Corporation and/or itsaffiliates. Other names may be trademarks of their respectiveowners.Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.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)mysql>
2.2.4 配置从数据库
[root@slave ~]# vim /etc/my.cnf//在[mysql]这段后面添加 datadir=/var/lib/mysql socket=/var/lib/mysql/mysql.sock server-id=2 //添加 从库的server-id比主库的大 relay-log=mysql-relay-bin //添加 # Disabling symbolic-links is recommended to prevent assorted security risks symbolic-links=0log-error=/var/log/mysqld.logpid-file=/var/run/mysqld/mysqld.pid
//重启mysql服务[root@slave ~]# systemctl restart mysqld[root@slave ~]# ss -anltState Recv-Q Send-Q Local Address:Port Peer Address:PortLISTEN 0 128 *:22 *:*LISTEN 0 128 [::]:22 [::]:*LISTEN 0 80 [::]:3306 [::]:*[root@slave ~]#//配置并启动主从复制[root@slave ~]# mysql -u root -p123456mysql: [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 2Server version: 5.7.22 MySQL Community Server (GPL)Copyright (c) 2000, 2018, Oracle and/or its affiliates. All rights reserved.Oracle is a registered trademark of Oracle Corporation and/or itsaffiliates. Other names may be trademarks of their respectiveowners.Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.mysql> change master to -> master_host='192.168.23.4', -> master_user='hqd', -> master_password='123456', -> master_log_file='mysql-bin.000001', -> master_log_pos=154;Query OK, 0 rows affected, 2 warnings (0.03 sec)mysql> start slave;Query OK, 0 rows affected (0.00 sec)mysql>//查看服务器状态mysql> show slave status \G*************************** 1. row *************************** Slave_IO_State: Waiting for master to send event Master_Host: 192.168.23.4 Master_User: hqd Master_Port: 3306 Connect_Retry: 60 Master_Log_File: mysql-bin.000002 Read_Master_Log_Pos: 154 Relay_Log_File: mysql-relay-bin.000004 Relay_Log_Pos: 367 Relay_Master_Log_File: mysql-bin.000002 Slave_IO_Running: Yes Slave_SQL_Running: Yes Replicate_Do_DB: Replicate_Ignore_DB:
3测试验证
在主服务器创建‘hqd’名称的库 查看从服务器是否同步mysql> create database hqd;Query OK, 1 row affected (0.00 sec)mysql> show databases;+--------------------+| Database |+--------------------+| information_schema || hqd || mysql || performance_schema || sys || test |+--------------------+6 rows in set (0.00 sec)mysql>
在从数据库中查看数据是否同步[root@slave ~]# mysql -uroot -p123456mysql: [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 5Server version: 5.7.22 MySQL Community Server (GPL)Copyright (c) 2000, 2018, Oracle and/or its affiliates. All rights reserved.Oracle is a registered trademark of Oracle Corporation and/or itsaffiliates. Other names may be trademarks of their respectiveowners.Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.mysql> show databases;+--------------------+| Database |+--------------------+| information_schema || hqd || mysql || performance_schema || sys || test |+--------------------+6 rows in set (0.00 sec)mysql>