MySQL主从复制

MySQL 主从复制原理

主从复制（也称 AB 复制）是指一台服务器充当主数据库服务器，另一台或多台服务器充当从数据库服务器，主服务器中的数据自动复制到从服务器之中。对于多级复制，数据库服务器既可充当主机，也可充当从机。MySQL默认采用异步复制方式。

主从复制的过程及原理可以总结如下：
  • master服务器将数据的改变记录二进制binlog日志，当master上的数据发生改变时，则将其改变写入二进制日志中。
  • slave服务器会在一定时间间隔内对master二进制日志进行探测其是否发生改变，如果发生改变，则开始一个I/OThread请求master二进制事件。
  • 同时主节点为每个I/O线程启动一个dump线程，用于向其发送二进制事件，并保存至从节点本地的中继日志中，从节点将启动SQL线程从中继日志中读取二进制日志，在本地重放，使得其数据和主节点的保持一致。
主从复制所需要的条件：
  • 开启二进制日志
  • 设置server-id
  • 创建同步账号
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CHANGE MASTER TO 
  MASTER_HOST='10.0.0.11',
  MASTER_USER='repluser',
  MASTER_PASSWORD='replpass',
  MASTER_LOG_FILE='mariadb-bin.xxxxXX,
  MASTER_LOG_POS=1567,
  MASTER_DELAY=interva1;       #可指定延迟复制实现访问误操作，单位秒
  
START SLAVE [IO THREAD SQL THREAD];    #
STOP SLAVE;
RESET SLAVE ALL;

SHOW SLAVE STATUS;

#查看 relaylog 事件，mysql8.0已取消中继日志
SHOW RELAYLOG EVENTS in 'relay-bin.00000x';


例一：将已有的mysql8.0单机变成主从复制架构

主节点 Rocky8-11 配置
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## 配置主节点配置文件，启用二进制日志，配置server-id
[root@Rocky8-11 ~]# mkdir /binlog/
[root@Rocky8-11 ~]# chown mysql. /binlog/
[root@Rocky8-11 ~]# vim /etc/my.cnf
[mysqld]
server-id=11
log-bin=/binlog/mysql-bin
[root@Rocky8-11 ~]# systemctl restart mysqld

## 完全备份
[root@Rocky8-11 ~]# mkdir /data
[root@Rocky8-11 ~]# mysqldump -A -F --master-data=1 --single-transaction > /data/all.sql 
[root@Rocky8-11 ~]# ls /data/
all.sql

## 创建复制用户并授权
[root@Rocky8-11 ~]# mysql 
01:28:55(root@localhost) [(none)] create user repluser@'10.0.0.%' identified by "123456";
01:30:11(root@localhost) [(none)] grant replication slave on *.* to repluser@'10.0.0.%';

## 将备份复制到从节点
[root@Rocky8-11 ~]# scp /data/all.sql  10.0.0.12:/data/
从节点 Rocky8-12 配置
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## 安装数据库、启用二进制日志，修改日志路径、设置server-id、启用数据库只读
[root@Rocky8-12 ~]# yum install mysql-server
[root@Rocky8-12 ~]# mkdir /binlog
[root@Rocky8-12 ~]# chown mysql. /binlog/
[root@Rocky8-12 ~]# vim /etc/my.cnf
[mysqld]
server-id=12
log-bin=/binlog/mysql-bin
read-only

## 修改备份文件
[root@Rocky8-12 ~]# vim /data/all.sql
CHANGE MASTER TO
    MASTER_HOST='10.0.0.11',
    MASTER_PORT=3306,
    MASTER_USER='repluser',
    MASTER_PASSWORD='123456',
    MASTER_LOG_FILE='mysql-bin.000002', 
    MASTER_LOG_POS=157;

## 还原数据库
[root@Rocky8-12 ~]# mysql 
mysql> set sql_log_bin=0;
mysql> source /data/all.sql

mysql> set sql_log_bin=1;
mysql> start slave;
查看主从服务状态

主要观察以下两项，确保状态为 Yes:

Slave_IO_Running: Yes
Slave_SQL_Running: Yes

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mysql> show slave status\G
*************************** 1. row ***************************
               Slave_IO_State: Waiting for source to send event
                  Master_Host: 10.0.0.11
                  Master_User: repluser
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: mysql-bin.000003
          Read_Master_Log_Pos: 573
               Relay_Log_File: Rocky8-12-relay-bin.000004
                Relay_Log_Pos: 789
        Relay_Master_Log_File: mysql-bin.000003
             Slave_IO_Running: Yes
            Slave_SQL_Running: 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: 573
              Relay_Log_Space: 1050
              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: 11
                  Master_UUID: f41fb64d-fb87-11ed-afcd-000c29bb093a
             Master_Info_File: mysql.slave_master_info
                    SQL_Delay: 0
          SQL_Remaining_Delay: NULL
      Slave_SQL_Running_State: Replica 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: 
       Master_public_key_path: 
        Get_master_public_key: 0
            Network_Namespace: 
1 row in set, 1 warning (0.00 sec)

例二：当Master节点故障，提升一个Slave做为新的Master

新master（10.0.0.12）：

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## 找到一个数据最新的节点，关闭readonly
[root@Rocky8-12 ~]# vim /etc/my.cnf
[mysqld]
server-id=12
log-bin=/binlog/mysql-bin
read-only=off

## 清除旧的master复制信息
[root@Rocky8-12 ~]# mysql 
mysql> set global read_only=off;
mysql> stop slave;
mysql> reset slave all;

## 完全备份
[root@Rocky8-12 ~]# mysqldump -A -F --single-transaction --master-data=1 > /data/backup.sql

## 分析旧master上的二进制日志，将未同步的二进制导出来，尽可能的恢复数据到新的master;

## 将备份传到其它slave
[root@Rocky8-12 ~]# scp /data/backup.sql 10.0.0.11:/data/

slave：

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[root@Rocky8-11 ~]# vim /data/backup.sql 
CHANGE MASTER TO 
    MASTER_HOST='10.0.0.12',
    MASTER_PORT=3306,
    MASTER_USER='repluser',
    MASTER_PASSWORD='123456',
    MASTER_LOG_FILE='mysql-bin.000003', 
    MASTER_LOG_POS=157;

[root@Rocky8-11 ~]# mysql 
(root@localhost) [(none)] stop slave;
(root@localhost) [(none)] reset slave all;
(root@localhost) [(none)] set sql_log_bin=off;
(root@localhost) [(none)] source /data/backup.sql;
(root@localhost) [(none)] set sql_log_bin=on;
(root@localhost) [(none)] show slave status\G
*************************** 1. row ***************************
               Slave_IO_State: Waiting for source to send event
                  Master_Host: 10.0.0.12
                  Master_User: repluser
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: mysql-bin.000003
          Read_Master_Log_Pos: 157
               Relay_Log_File: Rocky8-11-relay-bin.000002
                Relay_Log_Pos: 326
        Relay_Master_Log_File: mysql-bin.000003
             Slave_IO_Running: Yes
            Slave_SQL_Running: 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: 157
              Relay_Log_Space: 540
              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: 12
                  Master_UUID: e0a8221e-fde2-11ed-a771-000c29df68f9
             Master_Info_File: mysql.slave_master_info
                    SQL_Delay: 0
          SQL_Remaining_Delay: NULL
      Slave_SQL_Running_State: Replica 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: 
       Master_public_key_path: 
        Get_master_public_key: 0
            Network_Namespace: 
1 row in set, 1 warning (0.01 sec)

MySQL
#MariaDB #MySQL
MySQL主从复制
https://www.xcjyc.top/2023/05/25/MySQL主从复制/
作者
XCJYC
发布于
2023年5月25日
许可协议