change master to到一個不存在的主庫或主庫無法連接

本文測試當主庫無法連接時，從庫的複製狀態。

1.設置主庫

在從庫上， 將主庫設置爲//127.0.0.1或一個無法連接的主庫：

MASTER_HOST='//127.0.0.1'

或

MASTER_HOST='_'

設置複製：

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

mysql> 
mysql> CHANGE MASTER TO MASTER_HOST='//127.0.0.1', MASTER_PORT=3306,MASTER_AUTO_POSITION=1;
Query OK, 0 rows affected (0.01 sec)

mysql> start slave;
Query OK, 0 rows affected (0.00 sec)

2.查看複製狀態

mysql> show slave status\G
*************************** 1. row ***************************
               Slave_IO_State: Connecting to master
                  Master_Host: //127.0.0.1
                  Master_User: rep
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: 
          Read_Master_Log_Pos: 4
               Relay_Log_File: relay-bin.000001
                Relay_Log_Pos: 4
        Relay_Master_Log_File: 
             Slave_IO_Running: Connecting
            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: 0
              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: 0
Master_SSL_Verify_Server_Cert: No
                Last_IO_Errno: 2005
                Last_IO_Error: error connecting to master 'rep@//127.0.0.1:3306' - retry-time: 60  retries: 1
               Last_SQL_Errno: 0
               Last_SQL_Error: 
  Replicate_Ignore_Server_Ids: 
             Master_Server_Id: 0
                  Master_UUID: 
             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: 200129 12:29:28
     Last_SQL_Error_Timestamp: 
               Master_SSL_Crl: 
           Master_SSL_Crlpath: 
           Retrieved_Gtid_Set: 
            Executed_Gtid_Set: 43cf1658-41a4-11ea-9f90-080027974966:1-3
                Auto_Position: 1
         Replicate_Rewrite_DB: 
                 Channel_Name: 
           Master_TLS_Version: 
1 row in set (0.00 sec)

IO線程狀態

主庫無法連接，連接錯誤如下所示：

Slave_IO_State: Connecting to master
Master_Host: //127.0.0.1
Master_User: rep
Master_Port: 3306

Slave_IO_Running: Connecting
Slave_SQL_Running: Yes

Last_IO_Errno: 2005
Last_IO_Error: error connecting to master 'rep@//127.0.0.1:3306' - retry-time: 60  retries: 1

可以看到，IO線程正在嘗試連接主庫。

日誌位點信息

由於主庫無法連接，日誌位點相關的信息如下。

從庫已經接收的主庫日誌位點信息：

Master_Log_File: 
Read_Master_Log_Pos: 4

可以看到，日誌文件爲空，日誌起點從4開始。

已經執行到的主庫日誌位點信息：

Relay_Master_Log_File:
Exec_Master_Log_Pos: 0

已經執行的relay log信息：

Relay_Log_File: relay-bin.000001
Relay_Log_Pos: 4