|
CHANGE MASTER TO doesn't actually change the master when using prepared statements. This is problematic for users who use orchestration frameworks that rely on prepared statements.
As an example, we can first set up a master:
MariaDB [(none)]> CHANGE MASTER TO master_host='orig_master', master_user='repl', master_password='password', master_log_file='localhost-bin.000002', master_log_pos=330;
|
Query OK, 0 rows affected (0.05 sec)
|
|
MariaDB [(none)]> SHOW SLAVE STATUS\G
|
*************************** 1. row ***************************
|
Slave_IO_State:
|
Master_Host: orig_master
|
Master_User: repl
|
Master_Port: 3306
|
Connect_Retry: 60
|
Master_Log_File: localhost-bin.000002
|
Read_Master_Log_Pos: 330
|
Relay_Log_File: localhost-relay-bin.000001
|
Relay_Log_Pos: 4
|
Relay_Master_Log_File: localhost-bin.000002
|
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: 0
|
Last_Error:
|
Skip_Counter: 0
|
Exec_Master_Log_Pos: 330
|
Relay_Log_Space: 248
|
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: 0
|
Last_SQL_Error:
|
Replicate_Ignore_Server_Ids:
|
Master_Server_Id: 1
|
Master_SSL_Crl:
|
Master_SSL_Crlpath:
|
Using_Gtid: No
|
Gtid_IO_Pos:
|
1 row in set (0.00 sec)
|
Then let's try to change it via a prepared statement:
MariaDB [(none)]> SET @s := "CHANGE MASTER TO master_host='new_master', master_user='repl', master_password='password', master_log_file='localhost-bin.000002', master_log_pos=330";
|
Query OK, 0 rows affected (0.00 sec)
|
|
MariaDB [(none)]> PREPARE st FROM @s;
|
Query OK, 0 rows affected (0.00 sec)
|
Statement prepared
|
|
MariaDB [(none)]> EXECUTE st;
|
Query OK, 0 rows affected (0.04 sec)
|
|
MariaDB [(none)]> DEALLOCATE PREPARE st;
|
Query OK, 0 rows affected (0.00 sec)
|
We don't get any errors, so it sounds like things are OK, but the master hasn't actually been changed:
MariaDB [(none)]> SHOW SLAVE STATUS\G
|
*************************** 1. row ***************************
|
Slave_IO_State:
|
Master_Host: orig_master
|
Master_User: repl
|
Master_Port: 3306
|
Connect_Retry: 60
|
Master_Log_File: localhost-bin.000002
|
Read_Master_Log_Pos: 330
|
Relay_Log_File: localhost-relay-bin.000001
|
Relay_Log_Pos: 4
|
Relay_Master_Log_File: localhost-bin.000002
|
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: 0
|
Last_Error:
|
Skip_Counter: 0
|
Exec_Master_Log_Pos: 330
|
Relay_Log_Space: 248
|
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: 0
|
Last_SQL_Error:
|
Replicate_Ignore_Server_Ids:
|
Master_Server_Id: 1
|
Master_SSL_Crl:
|
Master_SSL_Crlpath:
|
Using_Gtid: No
|
Gtid_IO_Pos:
|
1 row in set (0.00 sec)
|
The wrong change goes into the error log as well:
150226 9:21:48 [Note] 'CHANGE MASTER TO executed'. Previous state master_host='orig_master', master_port='3306', master_log_file='localhost-bin.000002', master_log_pos='330'. New state master_host='orig_master', master_port='3306', master_log_file='localhost-bin.000002', master_log_pos='330'.
|
|