由于平台虚拟机宿主机迁移，导致一套MySQL主从库从节点故障，从节点服务终止，在服务启动后，恢复从节点同步服务，发现了如下报错：
mysql> show slave status\G;
*************************** 1. row ***************************
Slave_IO_State: Waiting for master to send event
Master_Host: XXXX
Master_User: cdbsync
Master_Port: 3366
Connect_Retry: 60
Master_Log_File: mysql-bin.007843
Read_Master_Log_Pos: 78338072
Relay_Log_File: nxscjdtsjkmysqlzc-mysql-master-2-367f7-0-relay-bin.023264
Relay_Log_Pos: 78930577
Relay_Master_Log_File: mysql-bin.007841
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: 13121
Last_Error: Relay log read failure: Could not parse relay log event entry. The possible reasons are: the master's binary log is corrupted (you can check this by running 'mysqlbinlog' on the binary log), the slave's relay log is corrupted (you can check this by running 'mysqlbinlog' on the relay log), a network problem, the server was unable to fetch a keyring key required to open an encrypted relay log file, or a bug in the master's or slave's MySQL code. If you want to check the master's binary log or slave's relay log, you will be able to know their names by issuing 'SHOW SLAVE STATUS' on this slave.
Skip_Counter: 0
Exec_Master_Log_Pos: 78930363
Relay_Log_Space: 300215564
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: 13121
Last_SQL_Error: Relay log read failure: Could not parse relay log event entry. The possible reasons are: the master's binary log is corrupted (you can check this by running 'mysqlbinlog' on the binary log), the slave's relay log is corrupted (you can check this by running 'mysqlbinlog' on the relay log), a network problem, the server was unable to fetch a keyring key required to open an encrypted relay log file, or a bug in the master's or slave's MySQL code. If you want to check the master's binary log or slave's relay log, you will be able to know their names by issuing 'SHOW SLAVE STATUS' on this slave.
Replicate_Ignore_Server_Ids:
Master_Server_Id: 2887743427
Master_UUID: e4a6bc6b-9de0-11eb-b5e2-fa163e5aaa5e
Master_Info_File: mysql.slave_master_info
SQL_Delay: 0
SQL_Remaining_Delay: NULL
Slave_SQL_Running_State:
Master_Retry_Count: 86400
Master_Bind:
Last_IO_Error_Timestamp:
Last_SQL_Error_Timestamp: 241016 02:50:23
Master_SSL_Crl:
Master_SSL_Crlpath:
Retrieved_Gtid_Set: e4a6bc6b-9de0-11eb-b5e2-fa163e5aaa5e:1-9339028
Executed_Gtid_Set: e4a6bc6b-9de0-11eb-b5e2-fa163e5aaa5e:1-9337179
Auto_Position: 1
Replicate_Rewrite_DB:
Channel_Name:
Master_TLS_Version:
Master_public_key_path:
Get_master_public_key: 1
Network_Namespace:
1 row in set (0.00 sec)
ERROR:
No query specified
mysql>
查看报错信息，提示由于日志损坏、网络问题或bug导致无法获取中继日志中的事件信息。
在尝试了跳过从节点错误方法后，依旧不能正常同步，报错还是一样。
于是，就计划reset slave，重新从中断的日志及position开始复制，整个操作流程如下：
确认Relay_Master_Log_File和Exec_Master_Log_Pos信息：
Relay_Master_Log_File: mysql-bin.007841
Exec_Master_Log_Pos: 78930363
STOP SLAVE;
RESET SLAVE;
CHANGE MASTER TO master_log_file='mysql-bin.007841', master_log_pos=78930363;
START SLAVE;
操作过程：
mysql> stop slave;
Query OK, 0 rows affected, 1 warning (0.00 sec)
mysql> RESET SLAVE;
Query OK, 0 rows affected (0.10 sec)
mysql> CHANGE MASTER TO master_log_file='mysql-bin.007841', master_log_pos=78930363;
ERROR 1776 (HY000): Parameters MASTER_LOG_FILE, MASTER_LOG_POS, RELAY_LOG_FILE and RELAY_LOG_POS cannot be set when MASTER_AUTO_POSITION is active.
根据提示信息，在从节点上设置master_auto_position为0：
mysql> change master to master_auto_position=0;
Query OK, 0 rows affected (0.08 sec)
mysql> CHANGE MASTER TO master_log_file='mysql-bin.007841', master_log_pos=78930363;
Query OK, 0 rows affected (0.06 sec)
重新启动slave：
mysql>
mysql> start slave;
Query OK, 0 rows affected (0.01 sec)
mysql> stop slave;
Query OK, 0 rows affected (0.03 sec)
同步正常后，将master_auto_position修改为1并重新启动同步：
mysql> change master to master_auto_position=
-> 1;
Query OK, 0 rows affected (0.05 sec)
mysql> start slave;
Query OK, 0 rows affected (0.02 sec)
mysql> show slave status\G;
*************************** 1. row ***************************
Slave_IO_State: Waiting for master to send event
Master_Host: XXXX
Master_User: cdbsync
Master_Port: 3366
Connect_Retry: 60
Master_Log_File: mysql-bin.007843
Read_Master_Log_Pos: 79142894
Relay_Log_File: nxscjdtsjkmysqlzc-mysql-master-2-367f7-0-relay-bin.000002
Relay_Log_Pos: 10529
Relay_Master_Log_File: mysql-bin.007843
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: 79142894
Relay_Log_Space: 10772
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: 2887743427
Master_UUID: e4a6bc6b-9de0-11eb-b5e2-fa163e5aaa5e
Master_Info_File: mysql.slave_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: e4a6bc6b-9de0-11eb-b5e2-fa163e5aaa5e:9339373-9339378
Executed_Gtid_Set: e4a6bc6b-9de0-11eb-b5e2-fa163e5aaa5e:1-9339378
Auto_Position: 1
Replicate_Rewrite_DB:
Channel_Name:
Master_TLS_Version:
Master_public_key_path:
Get_master_public_key: 1
Network_Namespace:
1 row in set (0.00 sec)
ERROR:
No query specified
mysql>
至此，整个同步报错处理完成。