mysq主从-优快云博客

本文链接：https://blog.youkuaiyun.com/cwt0314/article/details/99753265

本文介绍了MySQL主从复制的作用，包括实时灾备、读写分离和备份。详细阐述了主从复制的原理，涉及binlog日志、I/O线程和SQL线程的角色。并提供了详细的主从复制配置步骤，包括数据一致性、同步账号授权、主从数据库的配置与测试验证。

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文章目录

1. 主从简介
- 1.1 主从作用
- 1.2 主从形式
2. 主从复制原理
3. 主从复制配置

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

在这里插入图片描述

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

在这里插入图片描述
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	192.168.40.139	centos7/redhat7mysql-5.7	有数据
从数据库	192.168.40.140	centos7/redhat7mysql-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

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@cwt ~]# /usr/local/mysql/bin/mysql -uroot -pchen123 -e 'show databases;'
mysql: [Warning] Using a password on the command line interface can be insecure.
+--------------------+
| Database           |
+--------------------+
| information_schema |
| cwt                |
| mysql              |
| performance_schema |
| sys                |
+--------------------+

//再查看从库有哪些库
[root@cwt-slave ~]# mysql -uroot -pchen123 -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@cwt-master ~]# mysqldump -uroot -pchen123 --all-databases > /opt/all-20190819.sql
mysqldump: [Warning] Using a password on the command line interface can be insecure.
[root@cwt-master ~]# ls /opt
all-20190819.sql  chen  data
[root@cwt-master ~]# scp /opt/all-20190819.sql root@192.168.40.140:/opt
The authenticity of host '192.168.40.140 (192.168.40.140)' can't be established.
ECDSA key fingerprint is SHA256:6WZQmTmKKC6lRoBxMOI+pGk/Kq7yG+BozPz8se00xx8.
ECDSA key fingerprint is MD5:66:21:e7:57:71:80:0a:c1:bb:f1:06:37:ba:24:24:f1.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added '192.168.40.140' (ECDSA) to the list of known hosts.
root@192.168.40.140's password: 
all-20190819.sql                                                       100%  783KB  23.7MB/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@cwt-slave ~]# mysql -uroot -pchen123 < /opt/all-20190819.sql 
mysql: [Warning] Using a password on the command line interface can be insecure.
[root@cwt-slave ~]# mysql -uroot -pchen123 -e 'show databases;'
mysql: [Warning] Using a password on the command line interface can be insecure.
+--------------------+
| Database           |
+--------------------+
| information_schema |
| cwt                |
| mysql              |
| performance_schema |
| sys                |
+--------------------+

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> create user 'repl'@'192.168.40.140' identified by 'repl123';
Query OK, 0 rows affected (0.00 sec)

mysql> grant replication slave on *.* to 'repl'@'192.168.40.140';
Query OK, 0 rows affected (0.00 sec)

mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)
//此处ip为从库ip

3.2.3 配置主数据库

[root@cwt-master ~]# vim /etc/my.cnf
//在[mysqld]这段的后面加上如下内容
[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

#replication slave
log-bin=mysql-bin  //启用binlog日志
server-id=1  //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@cwt-master ~]# service mysqld restart
Shutting down MySQL.... SUCCESS! 
Starting MySQL.Logging to '/opt/data/cwt-master.err'.
 SUCCESS! 

//查看主库的状态
mysql> show master status;
ERROR 2006 (HY000): MySQL server has gone away
No connection. Trying to reconnect...
Connection id:    2
Current database: *** NONE ***

+------------------+----------+--------------+------------------+-------------------+
| 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@cwt-slave ~]# vim /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

server-id=2  //设置从库的唯一标识符，从库的server-id值必须大于主库的该值
relay-log=mysql-relay-bin   //启用中继日志relay-log


//重启从库的mysql服务
[root@cwt-slave ~]# service mysqld restart
Shutting down MySQL... SUCCESS! 
Starting MySQL.Logging to '/opt/data/cwt-slave.err'.
.. SUCCESS! 
[root@cwt-slave ~]# ss -antl
State       Recv-Q Send-Q       Local Address:Port                      Peer Address:Port              
LISTEN      0      128                      *:22                                   *:*                  
LISTEN      0      100              127.0.0.1:25                                   *:*                  
LISTEN      0      128                     :::22                                  :::*                  
LISTEN      0      100                    ::1:25                                  :::*                  
LISTEN      0      80                      :::3306                                :::*         

//配置并启动主从复制
mysql> change master to
    -> master_host='192.168.40.139',
    -> master_user='repl',
    -> master_password='repl123',
    -> master_log_file='mysql-bin.000001',
    -> master_log_pos=154;
Query OK, 0 rows affected, 2 warnings (0.11 sec)

mysql> start slave;
Query OK, 0 rows affected (0.00 sec)


//查看从服务器状态
mysql> show slave status \G
*************************** 1. row ***************************
               Slave_IO_State: Waiting for master to send event
                  Master_Host: 192.168.40.139
                  Master_User: repl
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: mysql-bin.000001
          Read_Master_Log_Pos: 154
               Relay_Log_File: mysql-relay-bin.000002
                Relay_Log_Pos: 320
        Relay_Master_Log_File: mysql-bin.000001
             Slave_IO_Running: Yes   //此处必须为Yes
            Slave_SQL_Running: Yes   //此处必须为Yes
              Replicate_Do_DB: 
          Replicate_Ignore_DB:

3.2.5 测试验证

在主服务器的student库的bj2表中插入数据：

mysql> select * from student;
+----+-------------+------+
| id | name        | age  |
+----+-------------+------+
|  1 | tom         |   20 |
|  2 | jerry       |   23 |
|  3 | wangqing    |   25 |
|  4 | sean        |   28 |
|  5 | zhangshan   |   26 |
|  6 | zhangshan   |   20 |
|  7 | lisi        | NULL |
|  8 | chenshuo    |   10 |
|  9 | wangwu      |    3 |
| 10 | qiuyi       |   15 |
| 11 | qiuxiaotian |   20 |
+----+-------------+------+
11 rows in set (0.00 sec)

mysql> insert into student values(12,'haha',20);
Query OK, 1 row affected (0.00 sec)

mysql> select * from student;
+----+-------------+------+
| id | name        | age  |
+----+-------------+------+
|  1 | tom         |   20 |
|  2 | jerry       |   23 |
|  3 | wangqing    |   25 |
|  4 | sean        |   28 |
|  5 | zhangshan   |   26 |
|  6 | zhangshan   |   20 |
|  7 | lisi        | NULL |
|  8 | chenshuo    |   10 |
|  9 | wangwu      |    3 |
| 10 | qiuyi       |   15 |
| 11 | qiuxiaotian |   20 |
| 12 | haha        |   20 |
+----+-------------+------+
12 rows in set (0.00 sec)

在从数据库中查看数据是否同步：

mysql> use cwt;
Database changed
mysql> select * from student;
+----+-------------+------+
| id | name        | age  |
+----+-------------+------+
|  1 | tom         |   20 |
|  2 | jerry       |   23 |
|  3 | wangqing    |   25 |
|  4 | sean        |   28 |
|  5 | zhangshan   |   26 |
|  6 | zhangshan   |   20 |
|  7 | lisi        | NULL |
|  8 | chenshuo    |   10 |
|  9 | wangwu      |    3 |
| 10 | qiuyi       |   15 |
| 11 | qiuxiaotian |   20 |
| 12 | haha        |   20 |
+----+-------------+------+
12 rows in set (0.00 sec)