Slave failed to initialize relay log info structure from the repository之出从复制出现问题

背景：

今天使用虚拟机搭建Mysql的主从复制，报错如下：

mysql> show slave status\G;
*************************** 1. row ***************************
               Slave_IO_State: 
                  Master_Host: 192.168.106.162
                  Master_User: slave
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: bin.000001
          Read_Master_Log_Pos: 926
               Relay_Log_File: me02-db-slave-relay-bin.000001
                Relay_Log_Pos: 4
        Relay_Master_Log_File: bin.000001
             Slave_IO_Running: No
            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: 1872
                   Last_Error: Slave failed to initialize relay log info structure from the repository
                 Skip_Counter: 0
          Exec_Master_Log_Pos: 926
              Relay_Log_Space: 154
              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: 1872
               Last_SQL_Error: Slave failed to initialize relay log info structure from the repository
  Replicate_Ignore_Server_Ids: 
             Master_Server_Id: 0
                  Master_UUID: 4d6f2019-82e5-11ea-8793-82a8fe88b138
             Master_Info_File: /home/data/dbdata/mysql/data/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: 200420 19:49:10
               Master_SSL_Crl: 
           Master_SSL_Crlpath: 
           Retrieved_Gtid_Set: 
            Executed_Gtid_Set: 
                Auto_Position: 0
         Replicate_Rewrite_DB: 
                 Channel_Name: 
           Master_TLS_Version: 

解决

Query OK, 0 rows affected (0.03 sec)

mysql> stop slave;
Query OK, 0 rows affected, 1 warning (0.00 sec)

mysql> CHANGE MASTER TO MASTER_HOST='192.168.106.162',MASTER_PORT=3306,MASTER_USER='slave',MASTER_PASSWORD='123456',MASTER_LOG_FILE='bin.000001', MASTER_LOG_POS=926;
Query OK, 0 rows affected, 2 warnings (0.04 sec)

mysql> start slave;

再次看从库的状态：

mysql> show slave status\G;
*************************** 1. row ***************************
               Slave_IO_State: Waiting for master to send event
                  Master_Host: 192.168.106.162
                  Master_User: slave
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: bin.000001
          Read_Master_Log_Pos: 926
               Relay_Log_File: me02-db-slave-relay-bin.000002
                Relay_Log_Pos: 314
        Relay_Master_Log_File: bin.000001
             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: 926
              Relay_Log_Space: 529
              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: 100
                  Master_UUID: 4d6f2019-82e5-11ea-8793-82a8fe88b138
             Master_Info_File: /home/data/dbdata/mysql/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)

从上面我们可以看到，主从已经恢复正常状态了，但是为了防止从库的写入导致主从不一致。我们可以讲从库设置成 read_olny 模式：

mysql> show global variables like "%read_only%";
+-----------------------+-------+
| Variable_name         | Value |
+-----------------------+-------+
| innodb_read_only      | OFF   |
| read_only             | OFF   |
| super_read_only       | OFF   |
| transaction_read_only | OFF   |
| tx_read_only          | OFF   |
+-----------------------+-------+
5 rows in set (0.01 sec)

mysql> set global read_only=1;
Query OK, 0 rows affected (0.00 sec)

mysql> show global variables like "%read_only%";
+-----------------------+-------+
| Variable_name         | Value |
+-----------------------+-------+
| innodb_read_only      | OFF   |
| read_only             | ON    |
| super_read_only       | OFF   |
| transaction_read_only | OFF   |
| tx_read_only          | OFF   |
+-----------------------+-------+
5 rows in set (0.00 sec)