不带MASTER_LOG_FILE,MASTER_LOG_POS参数，执行change master 语句复制异常

-------------分析日志-------------

1.先停止复制进程：

dbadmin@(none) 08:05:45>stop slave;

Query OK, 0 rows affected (0.10 sec)

2.查看丛库的状态及复制点坐标：

dbadmin@(none) 08:05:52>show slave status \G

*************************** 1. row ***************************

Slave_IO_State:

Master_Host: Master_Host

Master_User: Master_User

Master_Port: 3306

Connect_Retry: 60

Master_Log_File: mysql-bin.004476

Read_Master_Log_Pos: 289617713

Relay_Log_File: mysqld-relay-bin.000067

Relay_Log_Pos: 289617859

Relay_Master_Log_File: mysql-bin.004476

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: 289617713

Relay_Log_Space: 289618059

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: 612

1 row in set (0.00 sec)

3.查看一下master.info与relay-log.info文件中的信息，此时文件中记录的信息与show slave status显示的信息一致。

dbadmin@(none) 08:05:55>system cat /vobiledata/mysqldata/master.info;

18

mysql-bin.004476

289617713

Master_Host

repl

pass

3306

60

0

0

0.000

0

dbadmin@(none) 08:07:52>system cat /vobiledata/mysqldata/relay-log.info;

./mysqld-relay-bin.000067

289617859

mysql-bin.004476

289617713

4.不带MASTER_LOG_FILE,MASTER_LOG_POS参数，执行change master 语句，按照mysql官方文档的说法，执行语句后的复制点应该与之前的复制点一致，然而事实并非如此，执行该语句后，复制点被清空，记录在master.info和relay-log.info文件中的关于复制点的信息也被清空，如下：

dbadmin@(none) 08:08:24>CHANGE MASTER TO MASTER_HOST='Master_Host', MASTER_USER='repl', MASTER_PASSWORD='pass';

Query OK, 0 rows affected (0.11 sec)

dbadmin@(none) 08:08:55>show slave status \G

*************************** 1. row ***************************

Slave_IO_State:

Master_Host: Master_Host

Master_User: Master_User

Master_Port: 3306

Connect_Retry: 60

Master_Log_File:

Read_Master_Log_Pos: 4

Relay_Log_File: mysqld-relay-bin.000001

Relay_Log_Pos: 4

Relay_Master_Log_File:

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: 0

Relay_Log_Space: 107

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: 612

1 row in set (0.00 sec)

dbadmin@(none) 08:09:01>system cat /vobiledata/mysqldata/master.info;

18

4

Master_Host

repl

pass

3306

60

0

0

1800.000

0

60

0

0

0.000

0

dbadmin@(none) 08:09:17>system cat /vobiledata/mysqldata/relay-log.info;

./mysqld-relay-bin.000001

4

0

7859

mysql-bin.004476

289617713

重启复制进程，发现复制点被莫名奇妙的变成了另外一个值，这个值既不是执行语句前的复制点，也不是执行语句后的复制点。

dbadmin@(none) 08:09:26>start slave;

Query OK, 0 rows affected (0.00 sec)

dbadmin@(none) 08:09:47>show slave status \G

*************************** 1. row ***************************

Slave_IO_State: Waiting for master to send event

Master_Host: Master_Host

Master_User: Master_User

Master_Port: 3306

Connect_Retry: 60

Master_Log_File: mysql-bin.004430

Read_Master_Log_Pos: 9547576

Relay_Log_File: mysqld-relay-bin.000003

Relay_Log_Pos: 360

Relay_Master_Log_File: mysql-bin.004429

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: 214

Relay_Log_Space: 53239

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: 436462

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: 612

1 row in set (0.00 sec)

dbadmin@(none) 08:09:52>show slave status \G

*************************** 1. row ***************************

Slave_IO_State: Waiting for master to send event

Master_Host: Master_Host

Master_User: Master_User

Master_Port: 3306

Connect_Retry: 60

Master_Log_File: mysql-bin.004430

Read_Master_Log_Pos: 61188972

Relay_Log_File: mysqld-relay-bin.000003

Relay_Log_Pos: 360

Relay_Master_Log_File: mysql-bin.004429

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: 214

Relay_Log_Space: 53239

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: 436482

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: 612

1 row in set (0.00 sec)

赶紧停止复制，发现命令居然被长时间卡住，尝试停止mysql服务，超时异常，最后通过kill 系统进程，并重启mysql服务，重新设为正确的复制点。

dbadmin@(none) 08:10:12>stop slave;

查看error log，发现有如下日志：

160510 8:08:55 [Note] 'CHANGE MASTER TO executed'. Previous state master_host='192.168.110.113', master_port='3306', master_log_file='mysql-bin.004476', master_log_pos='289617713'. New state master_host='192.168.110.113', master_port='3306', master_log_file='',
master_log_pos='4'.

160510 8:09:47 [Note] Slave SQL thread initialized, starting replication in log 'FIRST' at position 0, relay log './mysqld-relay-bin.000001' position: 4

160510 8:09:47 [Note] Slave I/O thread: connected to master 'repl@192.168.110.113:3306',replication started in log 'FIRST' at position 4