故障起因

停止一臺從伺服器後換上了一臺新的mysql從伺服器

mysql> change master to master_host='20.0.0.12',
	-> master_user='myslave',
	-> master_password='123456',
	-> master_log_file='master-bin.000002',
	-> master_log_pos=154;
ERROR 3021 (HY000): This operation cannot be performed with a running slave io thread; run STOP SLAVE IO_THREAD FOR CHANNEL '' first.

解決故障

io執行緒開啟中無法對從伺服器進行修改，因此我們需要關閉io執行緒

mysql> STOP SLAVE IO_THREAD;   //關閉執行緒
Query OK, 0 rows affected (0.00 sec)

mysql> change master to master_host='20.0.0.12',   //指定主伺服器
    -> master_user='myslave',                 //管理使用者名稱稱
    -> master_password='123456',              //密碼
    -> master_log_file='master-bin.000002',   //二進位制檔案
    -> master_log_pos=154;                    //檔案位置引數

Query OK, 0 rows affected, 2 warnings (0.00 sec)    //提示成功

mysql> start SLAVE IO_THREAD;     //開啟io執行緒
Query OK, 0 rows affected (0.01 sec)