Mysql 一主一从

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	192.168.23.4	Centos7.8 mysql-5.7	有数据

从数据库	192.168.23.5	Centos7.8 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-tables

character_set_server=utf8

collation-server=utf8_general_ci

init_connect='SET NAMES utf8'

server_id=1

expire_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mysql

mysql> 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> quit

Bye

[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.sql

mysql: [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/mysql

socket=/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 -anlt

State      Recv-Q Send-Q                              Local Address:Port                                             Peer Address:Port

LISTEN     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 -p123456

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 2

Server 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 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 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=0

log-error=/var/log/mysqld.log

pid-file=/var/run/mysqld/mysqld.pid

//重启mysql服务

[root@slave ~]# systemctl restart mysqld

[root@slave ~]# ss -anlt

State      Recv-Q Send-Q                              Local Address:Port                                             Peer Address:Port

LISTEN     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 -p123456

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 2

Server 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 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> 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 -p123456

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 5

Server 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 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 |

| hqd                |

| mysql              |

| performance_schema |

| sys                |

| test               |

+--------------------+

6 rows in set (0.00 sec)

mysql>