解决方案 | MySQL DBA主从复制出错怎么办？

MySQL主从复制中若是出现错误，一般有哪些解决方法？通读本文，相信你会有答案。

主从复制中若是出现错误可以通过几个方法来进行解决：

1. 如果主从复制时发生了主键冲突，从而阻止了主从复制，可以使用sql_slave_skip_counter这个变量来忽略错误将其排除

2. 如果发生了较大的错误，可以考虑使用reset slave的方法重新配置从服务器来恢复错误

以下演示如何使用这两种方法解决错误，及相关操作的详细说明

• reset slave的使用方法

• 环境准备搭建主从同步

• 主节点配置

1. 修改配置文件

[root@Master ~]# vim /etc/my.cnf
[mysqld]
log-bin=/data/bin/mysql-bin
binlog-format=row
server-id=1

2. 创建二进制日志目录

[root@Master ~]# mkdir /data/bin
[root@Master ~]# chown -R mysql.mysql /data/bin

3. 启动mysqld服务

[root@Master ~]# systemctl start mariadb

4. 查看主服务器日志位置

[root@Master ~]# mysql -e "SHOW MASTER LOGS;"
+------------------+-----------+
| Log_name         | File_size |
+------------------+-----------+
| mysql-bin.000001 |     26753 |
| mysql-bin.000002 |    921736 |
| mysql-bin.000003 |       245 |
+------------------+-----------+

5. 创建一个用来复制数据的账户

[root@Master ~]# mysql -e "GRANT REPLICATION SLAVE ON *.* TO 'repluser'@'192.168.73.%' IDENTIFIED BY 'CentOS';"

从节点配置

1. 修改配置文件

[root@Slave ~]# vim /etc/my.cnf
[mysqld]
read-only
server-id=2

2. 启动服务

[root@Slave ~]# systemctl start mariadb

此处开始构建错误配置，以下所有CHANGE MASTER TO配置均为错误

3. 配置CHANGE MASTER TO

  MariaDB [(none)]> CHANGE MASTER TO
       ->   MASTER_HOST='master2.mycompany.com',
       ->   MASTER_USER='replication',
       ->   MASTER_PASSWORD='bigs3cret',
       ->   MASTER_PORT=3306,
       ->   MASTER_LOG_FILE='master2-bin.001',
       ->   MASTER_LOG_POS=4,
       ->   MASTER_CONNECT_RETRY=10;
    Query OK, 0 rows affected (0.00 sec)

4. 查看下SLAVE STATUS

    MariaDB [(none)]> SHOW SLAVE STATUS\G;
    *************************** 1. row ***************************
                  Slave_IO_State: 
                     Master_Host: master2.mycompany.com
                     Master_User: replication
                     Master_Port: 3306
                   Connect_Retry: 10
                 Master_Log_File: master2-bin.001
             Read_Master_Log_Pos: 4
                  Relay_Log_File: mariadb-relay-bin.000001
                   Relay_Log_Pos: 4
           Relay_Master_Log_File: master2-bin.001
                Slave_IO_Running: No
               Slave_SQL_Running: No
          ...以下省略...

5. 启动复制线程

MariaDB [(none)]> START SLAVE;

6. 再次查看SLAVE STATUS

    MariaDB [(none)]> SHOW SLAVE STATUS\G;
    *************************** 1. row ***************************
                  Slave_IO_State: Connecting to master
                     Master_Host: master2.mycompany.com
                     Master_User: replication
                     Master_Port: 3306
                   Connect_Retry: 10
                 Master_Log_File: master2-bin.001
             Read_Master_Log_Pos: 4
                  Relay_Log_File: mariadb-relay-bin.000001
                   Relay_Log_Pos: 4
           Relay_Master_Log_File: master2-bin.001
                Slave_IO_Running: Connecting
               Slave_SQL_Running: Yes
          ...以下省略...

线程已经正常启动

主服务器导入数据进行测试

 [root@Master ~]# mysql < hellodb_innodb.sql 
    [root@Master ~]# mysql -e "SHOW DATABASES;"
    +--------------------+
    | Database           |
    +--------------------+
    | information_schema |
    | hellodb            |
    | mysql              |
    | performance_schema |
    | test               |
    +--------------------+

从服务器查看是否同步(CHANGE MASTER TO信息不对怎么可能同步)

    MariaDB [(none)]> SHOW DATABASES;
    +--------------------+
    | Database           |
    +--------------------+
    | information_schema |
    | mysql              |
    | performance_schema |
    | test               |
    +--------------------+
    4 rows in set (0.00 sec)

以下为错误解决方法

由于错误发生在CHANGE MASTER TO所以此处将CHANG MASTER TO部分纠正就行

1. 首先将从服务器的复制线程停止

MariaDB [(none)]> STOP SLAVE;
Query OK, 0 rows affected (17.48 sec)

2. 将从服务器上的SLAVE信息重置

MariaDB [(none)]> RESET SLAVE;
Query OK, 0 rows affected (0.01 sec)

3. 重新输入正确的CHANGE MASTER TO信息

MariaDB [(none)]> CHANGE MASTER TO MASTER_HOST='192.168.73.110',MASTER_USER='repluser',MASTER_PASSWORD='centos',MASTER_PORT=3306,MASTER_LOG_FILE='mysql-bin.000003',MASTER_LOG_POS=245;
Query OK, 0 rows affected (0.01 sec)

4. 查看SLAVE STATUS;

MariaDB [(none)]> SHOW SLAVE STATUS\G;
*************************** 1. row ***************************
               Slave_IO_State: 
                  Master_Host: 192.168.73.110
                  Master_User: repluser
                  Master_Port: 3306
                Connect_Retry: 10
              Master_Log_File: mysql-bin.000003
          Read_Master_Log_Pos: 245
               Relay_Log_File: mariadb-relay-bin.000001
                Relay_Log_Pos: 4
        Relay_Master_Log_File: mysql-bin.000003
             Slave_IO_Running: No
            Slave_SQL_Running: No
              Replicate_Do_DB: 
#此处信息已经改为正确

5. 重新启动线程

MariaDB [(none)]> START SLAVE;
Query OK, 0 rows affected (0.00 sec)

6. 再次查看SLAVE STATUS;

MariaDB [(none)]> SHOW SLAVE STATUS\G;
*************************** 1. row ***************************
               Slave_IO_State: Waiting for master to send event
                  Master_Host: 192.168.73.110
                  Master_User: repluser
                  Master_Port: 3306
                Connect_Retry: 10
              Master_Log_File: mysql-bin.000003
          Read_Master_Log_Pos: 7384     #已经有数据复制过来了
               Relay_Log_File: mariadb-relay-bin.000002
                Relay_Log_Pos: 7668
        Relay_Master_Log_File: mysql-bin.000003
             Slave_IO_Running: Yes
            Slave_SQL_Running: Yes
#IO和SQL线程已经启动

7. 查看下从节点内的库是否已经同步

MariaDB [(none)]> SHOW DATABASES;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| hellodb            |          #hellodb库已经从主节点中复制过来了
| mysql              |
| performance_schema |
| test               |
+--------------------+
5 rows in set (0.01 sec)

• 其他说明：

如果生产中，发生主从节点之间的数据偏差较大并且迟迟不能同步，可以考虑将从服务器全部清除从新配置从服务器。

关于sql_slave_skip_counter的使用方法

当发生主键冲突时，从服务器会卡在出错的位置不再进行服务，此种错误一般会出现在主主复制或者从服务器已经占用了某条记录的情况下，此时可以使用此选项来忽略错误。

构建错误

此处继续沿用刚才的主从复制环境

1. 在从服务器上创建一条记录

MariaDB [(none)]> INSERT hellodb.teachers VALUE (5,'Li Xiaolong',30,'M');
Query OK, 1 row affected (0.00 sec)

2. 在主服务器上也创建一条主键相同的记录

MariaDB [(none)]> INSERT hellodb.teachers VALUE (5,'Xiao Yan',20,'M');
Query OK, 1 row affected (0.00 sec)

3. 返回从节点查看SLAVE STATUS

MariaDB [(none)]> SHOW SLAVE STATUS\G;
*************************** 1. row ***************************
               Slave_IO_State: Waiting for master to send event
                  Master_Host: 192.168.73.110
                  Master_User: repluser
                  Master_Port: 3306
                Connect_Retry: 10
              Master_Log_File: mysql-bin.000003
          Read_Master_Log_Pos: 7576
               Relay_Log_File: mariadb-relay-bin.000002
                Relay_Log_Pos: 7668
        Relay_Master_Log_File: mysql-bin.000003
             Slave_IO_Running: Yes
            Slave_SQL_Running: No
              Replicate_Do_DB: 
          Replicate_Ignore_DB: 
           Replicate_Do_Table: 
       Replicate_Ignore_Table: 
      Replicate_Wild_Do_Table: 
  Replicate_Wild_Ignore_Table: 
                   Last_Errno: 1062
                   Last_Error: Could not execute Write_rows event on table hellodb.teachers; Duplicate entry '5' for key 'PRIMARY', Error_code: 1062; handler error HA_ERR_FOUND_DUPP_KEY; the event's master log mysql-bin.000003, end_log_pos 7549
                 Skip_Counter: 0
          Exec_Master_Log_Pos: 7384
              Relay_Log_Space: 8156
              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: NULL
Master_SSL_Verify_Server_Cert: No
                Last_IO_Errno: 0
                Last_IO_Error: 
               Last_SQL_Errno: 1062
               Last_SQL_Error: Could not execute Write_rows event on table hellodb.teachers; Duplicate entry '5' for key 'PRIMARY', Error_code: 1062; handler error HA_ERR_FOUND_DUPP_KEY; the event's master log mysql-bin.000003, end_log_pos 7549
  Replicate_Ignore_Server_Ids: 
             Master_Server_Id: 1
1 row in set (0.00 sec)

4. 从节点已经出错，在主节点继续添加记录

MariaDB [(none)]> INSERT hellodb.teachers VALUE (6,'Xiao Xuner',20,'M');
Query OK, 1 row affected (0.00 sec)

5. 此时从节点已经不会再继续从主节点复制信息

MariaDB [(none)]> SELECT * FROM hellodb.teachers WHERE tid>4;
+-----+-------------+-----+--------+
| TID | Name      | Age |Gender |
+-----+-------------+-----+--------+
|   5 | Li Xiaolong |  30 | M      |   #此为刚才从节点添加的记录
+-----+-------------+-----+--------+
1 row in set (0.00 sec)

排错

1. 使用sql_slave_skip_counter变量忽略错误

MariaDB [(none)]> SET GLOBAL sql_slave_skip_counter=1;
Query OK, 0 rows affected (0.00 sec)

2. 停止线程并重新启动

MariaDB [(none)]> STOP SLAVE;
Query OK, 0 rows affected (0.00 sec)

MariaDB [(none)]> START SLAVE;
Query OK, 0 rows affected (0.00 sec)

3. 查看slave status状态，此时已经没有报错的信息

MariaDB [(none)]> SHOW SLAVE STATUS\G;
*************************** 1. row ***************************
               Slave_IO_State: Waiting for master to send event
                  Master_Host: 192.168.73.110
                  Master_User: repluser
                  Master_Port: 3306
                Connect_Retry: 10
              Master_Log_File: mysql-bin.000003
          Read_Master_Log_Pos: 7770
               Relay_Log_File: mariadb-relay-bin.000003
                Relay_Log_Pos: 529
        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: 7770
              Relay_Log_Space: 8634
              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: 1
1 row in set (0.00 sec)

4. 在从服务器上查看teachers表

MariaDB [(none)]> SELECT * FROM hellodb.teachers WHERE tid>4;
+-----+-------------+-----+--------+
| TID | Name        | Age | Gender |
+-----+-------------+-----+--------+
|   5 | Li Xiaolong |  30 | M      |
|   6 | Xiao Xuner  |  20 | M      |    #此时刚才在主节点插入的6号记录已经复制过来
+-----+-------------+-----+--------+
2 rows in set (0.00 sec)

以上为主从复制时出错的一些相关的修复方法，如果有帮助，感谢分享+在看；大家对什么内容感兴趣，也欢迎大家在留言区评论哦。

出处：https://www.linuxidc.com/Linux/2019-05/158646p2.htm

编辑：尹文敏

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