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，均存在着一些隐患：

• 用一台数据库服务器存放数据，如果服务器宕机则服务器内数据库的数据则会丢失
• 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

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（这里的备份并不是只全量，增量，差异等对数据库内数据备份，而是对服务器的一种备份）

1.2 主从形式

• 一主一从

一主一从：在主服务器上的写操作会被复制进从服务器

• 主主复制

主主复制：互为主备，相互复制写入的信息

• 一主多从---扩展系统读取的性能，因为读是在从库读取的

一主多从：当公司某业务读取量特别大时，可将数据库主备做成一主多从，将从服务器用作业务的读服务器，可以在流量大时保证服务质量

• 多主一从---5.7开始支持

多主一从：公司业务写入量大的时候，如春运抢票软件，双十一电商平台购物。可将服务器做成多主一从，保证流量大时写入业务的服务质量

• 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）

3.1 主从复制两台新服务器无数据时的配置

注意: 请将防火请关闭或设置防火墙规则

因为是新的服务器所以两边的数据一定相同，所以跳过了第一步同步主从的数据

需求：搭建两台MySQL服务器，一台作为主服务器（master164），一台作为从服务器（slaver163），主服务器进行写操作，从服务器进行读操作

环境说明：

3.1.1 mysql安装

请使用二进制mysql包安装

3.1.2 在主数据库里创建一个同步账号授权给从数据库使用

[root@master164 ~]# mysql -uroot -pcwh123!
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 3
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> grant replication slave on *.* to 'repl'@'192.168.112.163' identified by 'cwh123!';
Query OK, 0 rows affected, 1 warning (0.00 sec)

mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)

3.1.3 配置主数据库

[root@master164 ~]# vim /etc/my.cnf
[mysqld]
basedir = /usr/local/mysql
datadir = /opt/data
socket = /tmp/mysql.sock
log-bin = mysql-master-bin
server-id = 1
port = 3306
pid-file = /opt/data/mysql.pid
user = mysql
skip-name-resolve

//重启mysql服务
[root@master164 ~]# /etc/init.d/mysqld restart
Shutting down MySQL.. SUCCESS! 
Starting MySQL. SUCCESS! 
[root@master164 ~]# 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      80                :::3306                          :::*                  
LISTEN      0      32                :::21                            :::*                  
LISTEN      0      128               :::22                            :::*                  
LISTEN      0      100              ::1:25                            :::*    

//查看主库的状态
mysql> show master status;
+-------------------------+----------+--------------+------------------+-------------------+
| File                    | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set |
+-------------------------+----------+--------------+------------------+-------------------+
| mysql-master-bin.000002 |      154 |              |                  |                   |
+-------------------------+----------+--------------+------------------+-------------------+
  //注意其中的file下的文件是主服务器的log-bin日志
  //position下的数字是后面从数据库需要用到的起始位置
  

3.1.4 配置从数据库

symbolic-links=0
[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 = 6
relay-log = mysql-relay-bin

//重启从库的mysql服务
[root@slaver163 ~]# /etc/init.d/mysqld restart
Shutting down MySQL.. SUCCESS! 
Starting MySQL. SUCCESS! 
[root@slaver163 ~]# 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      80                :::3306                          :::*                  
LISTEN      0      128               :::22                            :::*                  
LISTEN      0      100              ::1:25                            :::*                  

//配置并启动主从复制
mysql> change master to master_host='192.168.112.164',master_user='repl',master_password='cwh123!',master_log_file='mysql-master-bin.000002',master_log_pos=154;
Query OK, 0 rows affected, 2 warnings (0.01 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: 192.168.112.164
                  Master_User: repl
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: mysql-master-bin.000002
          Read_Master_Log_Pos: 154
               Relay_Log_File: mysql-relay-bin.000002
                Relay_Log_Pos: 327
        Relay_Master_Log_File: mysql-master-bin.000002
             Slave_IO_Running: Yes //slave的io线程yes 为成功启动
            Slave_SQL_Running: Yes //slave的SQL线程yes为成功启动

3.1.5 测试验证

//在主服务器新建cwh库并新建aaa表向aaa表中插入数据：
mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
+--------------------+
4 rows in set (0.00 sec)

mysql> create database cwh;
Query OK, 1 row affected (0.00 sec)

mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| cwh                |
| mysql              |
| performance_schema |
| sys                |
+--------------------+
5 rows in set (0.00 sec)

mysql> use cwh;
Database changed
mysql> create table aaa(name varchar(100) not null,age tinyint);
Query OK, 0 rows affected (0.05 sec)

mysql> show tables;
+---------------+
| Tables_in_cwh |
+---------------+
| aaa           |
+---------------+
1 row in set (0.00 sec)

mysql> insert into aaa values('tom',20),('jerry',30);
Query OK, 2 rows affected (0.01 sec)
Records: 2  Duplicates: 0  Warnings: 0

mysql> select * from aaa;
+-------+------+
| name  | age  |
+-------+------+
| tom   |   20 |
| jerry |   30 |
+-------+------+
2 rows in set (0.00 sec)

//在从数据库中查看数据是否同步：
mysql> select * from cwh.aaa;
+-------+------+
| name  | age  |
+-------+------+
| tom   |   20 |
| jerry |   30 |
+-------+------+
2 rows in set (0.00 sec)
  //可以看出同步成功了

3.1.6 从服务器IO线程和SQL线程变化

//主服务器每次重启后log-bin日志文件的编号会发生改变
mysql> show master status;
+-------------------------+----------+--------------+------------------+-------------------+
| File                    | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set |
+-------------------------+----------+--------------+------------------+-------------------+
| mysql-master-bin.000003 |      154 |              |                  |                   |
+-------------------------+----------+--------------+------------------+-------------------+
1 row in set (0.00 sec)
mysql> exit
Bye
[root@master164 ~]# /etc/init.d/mysqld restart
Shutting down MySQL............ SUCCESS! 
Starting MySQL. SUCCESS! 

[root@master164 ~]# mysql -uroot -pcwh123!
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-master-bin.000004 |      154 |              |                  |                   |
+-------------------------+----------+--------------+------------------+-------------------+
1 row in set (0.00 sec)
   //可以看出已经改变变为00004


mysql> show slave status\G;
*************************** 1. row ***************************
               Slave_IO_State: Reconnecting after a failed master event read
                  Master_Host: 192.168.112.164
                  Master_User: repl
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: mysql-master-bin.000004
          Read_Master_Log_Pos: 154
               Relay_Log_File: mysql-relay-bin.000006
                Relay_Log_Pos: 381
        Relay_Master_Log_File: mysql-master-bin.000004
             Slave_IO_Running: Connecting
            Slave_SQL_Running: Yes
    //可以看出IO线程状态从yes变为connecting

//等待一段时间后在查看从服务器
mysql> show slave status\G;
*************************** 1. row ***************************
               Slave_IO_State: Waiting for master to send event
                  Master_Host: 192.168.112.164
                  Master_User: repl
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: mysql-master-bin.000005
          Read_Master_Log_Pos: 154
               Relay_Log_File: mysql-relay-bin.000008
                Relay_Log_Pos: 381
        Relay_Master_Log_File: mysql-master-bin.000005
             Slave_IO_Running: Yes
            Slave_SQL_Running: Yes
    //可以看出IO线程变为yes，也就说明此时同步完成

3.2主从复制两台主服务器有数据时的配置

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：

3.2.1 mysql安装

安装MySQL二进制包

3.2.2 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 |
| cwh                |
| mysql              |
| performance_schema |
| sys                |
+--------------------+
5 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)

//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)

mysql> 

    //此时在原来终端上创建一个库试试读锁是否生效
    //此锁表的终端必须在全备配置完成以后才能退出

//全备主库并将备份文件传送到从库
[root@master164 ~]# mysqldump -uroot -pcwh123! --all-databases > /opt/master_all_backup.sql
mysqldump: [Warning] Using a password on the command line interface can be insecure.
[root@master164 ~]# ls /opt/
data  master_all_backup.sql  yumbak
[root@master164 ~]# scp /opt/master_all_backup.sql root@192.168.112.165:/opt/
root@192.168.112.165's password: 
master_al 100%  203   199.6KB/s   00:00 

//解除主库的锁表状态，直接退出交互式界面即可

//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@slave165 ~]# mysql -uroot -pcwh123! < /opt/master_all_backup.sql 
mysql: [Warning] Using a password on the command line interface can be insecure.
[root@slave165 ~]# mysql -uroot -pcwh123! -e 'show databases;'
mysql: [Warning] Using a password on the command line interface can be insecure.
+--------------------+
| Database           |
+--------------------+
| information_schema |
| cwh                |
| mysql              |
| performance_schema |
| sys                |
+--------------------+

3.2.3 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'@'192.168.112.165' identified by 'cwh123!';
Query OK, 0 rows affected, 1 warning (0.00 sec)

mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)

3.2.4 配置主数据库

[root@master164 ~]# vim /etc/my.cnf
[mysqld]
basedir = /usr/local/mysql
datadir = /opt/data
socket = /tmp/mysql.sock
log-bin = mysql-master-bin
server-id = 1
port = 3306
pid-file = /opt/data/mysql.pid
user = mysql
skip-name-resolve

//重启mysql服务
[root@master164 ~]# /etc/init.d/mysqld restart
Shutting down MySQL.. SUCCESS! 
Starting MySQL. SUCCESS! 

//查看主库的状态
mysql> show master status;
+-------------------------+----------+--------------+------------------+-------------------+
| File                    | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set |
+-------------------------+----------+--------------+------------------+-------------------+
| mysql-master-bin.000007 |     603 |              |                  |                   |
+-------------------------+----------+--------------+------------------+-------------------+
1 row in set (0.00 sec)

3.2.5 配置从数据库

[root@slave165 ~]# 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 = 8
relay-log = mysql-relay-bin

//重启从库的mysql服务
[root@slave165 ~]# /etc/init.d/mysqld restart
Shutting down MySQL.. SUCCESS! 
Starting MySQL. SUCCESS! 

//配置并启动主从复制
mysql> change master to master_host='192.168.112.164',master_user='repl',master_password='cwh123!',master_log_file='mysql-master-bin.000007',master_log_pos=603;
Query OK, 0 rows affected, 2 warnings (0.00 sec)

mysql> start slave;
Query OK, 0 rows affected (0.01 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: 192.168.112.164
                  Master_User: repl
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: mysql-master-bin.000007
          Read_Master_Log_Pos: 603
               Relay_Log_File: mysql-relay-bin.000002
                Relay_Log_Pos: 327
        Relay_Master_Log_File: mysql-master-bin.000007
             Slave_IO_Running: Yes
            Slave_SQL_Running: Yes

3.2.6 测试验证

//在主服务器的创建库：
mysql> create database ddl;
Query OK, 1 row affected (0.01 sec)
mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| cwh                |
| ddl                |
| mysql              |
| performance_schema |
| sys                |
+--------------------+
6 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 |
| cwh                |
| ddl                |
| mysql              |
| performance_schema |
| sys                |
+--------------------+
6 rows in set (0.00 sec)

  //可以看出数据同步成功

Mysql主从

原文：https://www.cnblogs.com/chengweihong/p/10877202.html