MySQL主从配置

Posted 2023-05-08

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参考技术A

mysql主从又叫做Replication、AB复制。简单讲就是A和B两台机器做主从后，在A上写数据，另外一台B也会跟着写数据，两者数据实时同步；
MySQL主从是基于binlog的，主上须开启binlog才能进行主从。
主从过程大致有3个步骤
1）主将更改操作记录到binlog里；
2）从将主的binlog事件(sql语句)同步到从本机上并记录在relaylog里；
3）从根据relaylog里面的sql语句按顺序执行；
主上有一个log dump线程，用来和从的I/O线程传递binlog
从上有两个线程，其中I/O线程用来同步主的binlog并生成relaylog，另外一个SQL线程用来把relaylog里面的sql语句落地

同步参数“主”“从”上均可设置，只要设置一个就可以了

MySQL传统主从配置

文章目录

mysql主从

mysql主从

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？

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

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

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

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，两台台作为从服务器，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	192.168.96.129	centos8/redhat8 mysql-5.7	无数据
从数据库	192.168.96.133	centos8/redhat8 mysql-5.7	无数据
从数据库	192.168.96.134	centos8/redhat8 mysql-5.7	无数据

1 mysql安装

分别在主从三台服务器上安装mysql-5.7版本，此处略过安装步骤，若有疑问请参考二进制格式安装MySQL

2 mysql主从配置

2.1先把三台服务器的防火墙关闭

#主
[root@localhost ~]# systemctl stop firewalld
[root@localhost ~]# systemctl status firewalld
● firewalld.service - firewalld - dynamic firewall daemon
   Loaded: loaded (/usr/lib/systemd/system/firewalld.service; disabled; v>
   Active: inactive (dead)
     Docs: man:firewalld(1)

May 11 22:30:55 localhost.localdomain systemd[1]: Starting firewalld - dy>
May 11 22:30:56 localhost.localdomain systemd[1]: Started firewalld - dyn>
May 11 22:30:57 localhost.localdomain firewalld[932]: WARNING: AllowZoneD>
May 11 23:10:02 localhost.localdomain systemd[1]: Stopping firewalld - dy>
May 11 23:10:03 localhost.localdomain systemd[1]: firewalld.service: Succ>
May 11 23:10:03 localhost.localdomain systemd[1]: Stopped firewalld - dyn>
[root@localhost ~]# systemctl disable firewalld
[root@localhost ~]# getenforce 
Enforcing
[root@localhost ~]# setenforce 0
[root@localhost ~]# getenforce 
Permissive
#从1
[root@localhost ~]# systemctl stop firewalld
[root@localhost ~]# systemctl stastus firewalld
Unknown operation stastus.
[root@localhost ~]# systemctl status firewalld
● firewalld.service - firewalld - dynamic firewall daemon
   Loaded: loaded (/usr/lib/systemd/system/firewalld.service; enabled; ve>
   Active: inactive (dead) since Tue 2021-05-11 23:11:38 CST; 21s ago
     Docs: man:firewalld(1)
  Process: 916 ExecStart=/usr/sbin/firewalld --nofork --nopid $FIREWALLD_>
 Main PID: 916 (code=exited, status=0/SUCCESS)

May 11 22:27:06 localhost.localdomain systemd[1]: Starting firewalld - dy>
May 11 22:27:07 localhost.localdomain systemd[1]: Started firewalld - dyn>
May 11 22:27:08 localhost.localdomain firewalld[916]: WARNING: AllowZoneD>
May 11 23:11:38 localhost.localdomain systemd[1]: Stopping firewalld - dy>
May 11 23:11:38 localhost.localdomain systemd[1]: firewalld.service: Succ>
May 11 23:11:38 localhost.localdomain systemd[1]: Stopped firewalld - dyn>
[root@localhost ~]# systemctl disable firewalld
Removed /etc/systemd/system/multi-user.target.wants/firewalld.service.
Removed /etc/systemd/system/dbus-org.fedoraproject.FirewallD1.service.
[root@localhost ~]# getenforce 
Enforcing
[root@localhost ~]# setenforce 0
[root@localhost ~]# setenforce 0
[root@localhost ~]# getenforce 
Permissive
#从2
[root@localhost ~]# systemctl stop firewalld
[root@localhost ~]# systemctl status firewalld
● firewalld.service - firewalld - dynamic firewall daemon
   Loaded: loaded (/usr/lib/systemd/system/firewalld.service; enabled; ve>
   Active: inactive (dead) since Tue 2021-05-11 23:13:21 CST; 6s ago
     Docs: man:firewalld(1)
  Process: 932 ExecStart=/usr/sbin/firewalld --nofork --nopid $FIREWALLD_>
 Main PID: 932 (code=exited, status=0/SUCCESS)

May 11 22:26:44 localhost.localdomain systemd[1]: Starting firewalld - dy>
May 11 22:26:44 localhost.localdomain systemd[1]: Started firewalld - dyn>
May 11 22:26:45 localhost.localdomain firewalld[932]: WARNING: AllowZoneD>
May 11 23:13:21 localhost.localdomain systemd[1]: Stopping firewalld - dy>
May 11 23:13:21 localhost.localdomain systemd[1]: firewalld.service: Succ>
May 11 23:13:21 localhost.localdomain systemd[1]: Stopped firewalld - dyn>
[root@localhost ~]# systemctl disable firewalld
Removed /etc/systemd/system/multi-user.target.wants/firewalld.service.
Removed /etc/systemd/system/dbus-org.fedoraproject.FirewallD1.service.
[root@localhost ~]# getenforce 
Enforcing
[root@localhost ~]# setenforce 0
[root@localhost ~]# getenforce 
Permissive

2.2 查看各个服务器中的mysq中数据是否一致

# 主
mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
+--------------------+
4 rows in set (0.00 sec)
# 从1
mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
+--------------------+
4 rows in set (0.01 sec)
# 从2
mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
+--------------------+
4 rows in set (0.01 sec)

如果数据库中的数据不一样，则需要全备主服务器中数据，然后恢复到从服务器中，备份时使用以下命令锁表，使其不能插入数据。

mysql> FLUSH TABLES WITH READ LOCK;

全量备份若有疑问请参考全量备份

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> CREATE USER 'bwxh'@'192.168.96.133' IDENTIFIED BY 'bwxh123';
Query OK, 0 rows affected (0.00 sec)
mysql> GRANT REPLICATION SLAVE ON *.* TO 'bwxh'@'192.168.96.133';
Query OK, 0 rows affected (0.00 sec)
mysql> CREATE USER 'bwxh'@'192.168.96.134' IDENTIFIED BY 'bwxh123';
Query OK, 0 rows affected (0.00 sec)
mysql> GRANT REPLICATION SLAVE ON *.* TO 'bwxh'@'192.168.96.134';
Query OK, 0 rows affected (0.00 sec)

2.4配置主数据库

[root@localhost ~]# vim /etc/my.cnf
//添加以下内容
[mysqld3306]
datadir = /opt/data/3306
port = 3306
socket = /tmp/mysql3306.sock
pid-file = /opt/data/3306/mysql_3306.pid
log-error=/var/log/3306.log
log-bin=mysqld-bin		//启用binlog日志
server-id=10			//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@localhost ~]# service 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 |
+-------------------+----------+--------------+------------------+-------------------+
| mysqld-bin.000001 |      154 |              |                  |                   |
+-------------------+----------+--------------+------------------+-------------------+
1 row in set (0.00 sec)

2.5 配置从数据库

从1

[root@localhost ~]# vim /etc/my.cnf
//添加以下内容
[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
server-id=20		//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@localhost ~]#  service mysqld restart
Shutting down MySQL.. SUCCESS! 
Starting MySQL. SUCCESS!

//配置并启动主从复制
ysql> CHANGE MASTER TO
    -> MASTER_HOST='192.168.96.129',
    -> MASTER_USER='bwxh',
    -> MASTER_PASSWORD='bwxh123',
    -> MASTER_LOG_FILE='mysqld-bin.000001',
    -> MASTER_LOG_POS=154;
Query OK, 0 rows affected, 2 warnings (0.01 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: 192.168.96.129
                  Master_User: bwxh
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: mysqld-bin.000001
          Read_Master_Log_Pos: 154
               Relay_Log_File: mysql-relay-bin.000002
                Relay_Log_Pos: 321
        Relay_Master_Log_File: mysqld-bin.000001
             Slave_IO_Running: Yes		//此次必须为yes
            Slave_SQL_Running: Yes		//此次必须为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: 154
              Relay_Log_Space: 528
              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: 6b52bbf9-b198-11eb-9706-000c29a69e07
             Master_Info_File: /opt/data/master.info
                    SQL_Delay: 0
          SQL_Remaining_Delay: NULL
      Slave_SQL_Running_State: Slave 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: 
1 row in set (0.00 sec)

从2

[root@localhost ~]# vim /etc/my.cnf
//添加以下内容
[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
server-id=20		//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@localhost ~]#  service mysqld restart
Shutting down MySQL.. SUCCESS! 
Starting MySQL. SUCCESS!

//配置并启动主从复制
ysql> CHANGE MASTER TO
    -> MASTER_HOST='192.168.96.129',
    -> MASTER_USER='bwxh',
    -> MASTER_PASSWORD='bwxh123',
    -> MASTER_LOG_FILE='mysqld-bin.000001',
    -> MASTER_LOG_POS=154;
Query OK, 0 rows affected, 2 warnings (0.01 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: 192.168.96.129
                  Master_User: bwxh
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: mysqld-bin.000001
          Read_Master_Log_Pos: 154
               Relay_Log_File: mysql-relay-bin.000002
                Relay_Log_Pos: 321
        Relay_Master_Log_File: mysqld-bin.000001
             Slave_IO_Running: Yes		//此次必须为yes
            Slave_SQL_Running: Yes		//此次必须为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: 154
              Relay_Log_Space: 528
              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: 6b52bbf9-b198-11eb-9706-000c29a69e07
             Master_Info_File: /opt/data/master.info
                    SQL_Delay: 0
          SQL_Remaining_Delay: NULL
      Slave_SQL_Running_State: Slave 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: 
1 row in set (0.00 sec)

2.6 测试验证

在主服务器的数据库中创建bwxh库，在bwxh库中创建表student并插入数据：

mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
+--------------------+
4 rows in set (0.00 sec)
mysql> create database hyh;
Query OK, 1 row affected (0.00 sec)

mysql> use hyh;
Database changed

mysql> insert student(name,age) values('tom',18),('jerry',23),('zhangshan',
,20);
Query OK, 3 rows affected (0.07 sec)
Records: 3  Duplicates: 0  Warnings: 0

mysql> select * from student;
+----+-----------+------+
| id | name      | age  |
+----+-----------+------+
|  1 | tom       |   18 |
|  2 | jerry     |   23 |
|  3 | zhangshan |   20 |
+----+-----------+------+
3 rows in set (0.00 sec)

在从数据库中查看数据是否同步：

//从1
mysql> select * from hyh.student;
+----+-----------+------+
| id | name      | age  |
+----+-----------+------+
|  1 | tom       |   18 |
|  2 | jerry     |   23 |
|  3 | zhangshan |   20 |
+----+-----------+------+
3 rows in set (0.01 sec)
//从2
mysql> select * from hyh.student;
+----+-----------+------+
| id | name      | age  |
+----+-----------+------+
|  1 | tom       |   18 |
|  2 | jerry     |   23 |
|  3 | zhangshan |   20 |
+----+-----------+------+
3 rows in set (0.00 sec)

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