mysql 1236 bug_mysql-error 1236

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#mysql 1236 bug

本文介绍了一种常见的MySQL复制错误1236及其解决方法。通过调整slave节点的复制起点，成功解决了因主服务器意外重启而导致的同步问题。

今天其中一台游戏服务器的数据库mysql master当机，系统变为只读模式，重启后进入安全模式，执行fsck后恢复正常。服务器起来之后mysql启动正常，但一台slave却一直出现同步错误。

登录后查看，发现以下错误：mysql> show slave status\G

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

Slave_IO_State:

Master_Host: 10.90.13.238

Master_User: slave

Master_Port: 3306

Connect_Retry: 60

Master_Log_File: mysql-bin.000949

Read_Master_Log_Pos: 277562491

Relay_Log_File: mysql-relay-bin.001616

Relay_Log_Pos: 277562637

Relay_Master_Log_File: mysql-bin.000949

Slave_IO_Running: No

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: 1

Exec_Master_Log_Pos: 277562491

Relay_Log_Space: 277562836

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: 1236

Last_IO_Error: Got fatal error 1236 from master when reading data from binary log: 'Client requested master to start replication from impossible position; the first event 'mysql-bin.000949' at 277562491, the last event read from './mysql-bin.000949' at 4, the last byte read from './mysql-bin.000949' at 4.'

Last_SQL_Errno: 0

Last_SQL_Error:

Replicate_Ignore_Server_Ids:

Master_Server_Id: 4

1 row in set (0.00 sec)

错误为：

Got fatal error 1236 from master when reading data from binary log: 'Client requested master to start replication from impossible position; the first event 'mysql-bin.000949' at 277562491, the last event read from './mysql-bin.000949' at 4, the last byte read from './mysql-bin.000949' at 4.'

这个错误之前也遇到过，但没有具体记录下来，于是网上找资料。

参考了这几个资料：

出现这样的错误原因很简单，原本的slave在master当机前一直在执行同步的动作，当master当机重启mysql恢复之后，会重新开一个新的binlog继续写，但slave不知道发生了这件事，所以还在问上次同步的那个binlog文件和读到得那个位置。

要确定这个情况，我执行了如下的操作：

1. 检查master的位置mysql> show master status\G

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

File: mysql-bin.000950

Position: 336492640

Binlog_Do_DB:

Binlog_Ignore_DB:

1 row in set (0.00 sec)

mysql> show master status;

2. 检查master上binlog的大小和最新的修改时间：[root@d1 ~]# ll /data/mysql/mysql-bin.*

-rw-rw---- 1 mysql mysql 1073742473 Nov 17 10:38 /data/mysql/mysql-bin.000944

-rw-rw---- 1 mysql mysql 1073742022 Nov 18 12:44 /data/mysql/mysql-bin.000945

-rw-rw---- 1 mysql mysql 1073745576 Nov 19 15:31 /data/mysql/mysql-bin.000946

-rw-rw---- 1 mysql mysql 1073745324 Nov 21 05:03 /data/mysql/mysql-bin.000947

-rw-rw---- 1 mysql mysql 1073742027 Nov 22 16:09 /data/mysql/mysql-bin.000948

-rw-rw---- 1 mysql mysql 277553623 Nov 23 05:07 /data/mysql/mysql-bin.000949

-rw-rw---- 1 mysql mysql 337157571 Nov 23 18:04 /data/mysql/mysql-bin.000950

-rw-rw---- 1 mysql mysql 133 Nov 23 08:06 /data/mysql/mysql-bin.index[root@d1 ~]# du /data/mysql/mysql-bin.* -sh

1.1G /data/mysql/mysql-bin.000944

1.1G /data/mysql/mysql-bin.000945

1.1G /data/mysql/mysql-bin.000946

1.1G /data/mysql/mysql-bin.000947

1.1G /data/mysql/mysql-bin.000948

265M /data/mysql/mysql-bin.000949

323M /data/mysql/mysql-bin.000950

4.0K /data/mysql/mysql-bin.index

从这里可以发现，000949是mysql在系统崩溃的时候最后写过的文件，在恢复之后重新建立了一个新的

000950，从时间和大小的条件可以判断，正常情况下mysql-bin.000949应该会写到1.1G的时候才会重新建立新的文件继续写，现在的情况是服务器宕机导致binlog crash了，所以mysql启动后会重新建立一个新的binlog文件。

3. 在slave上执行如下命令：mysql> stop slave

-> ;

Query OK, 0 rows affected (0.00 sec)

mysql> change master to master_host='10.90.13.238', master_user='slave' ,MASTER_PASSWORD='',MASTER_LOG_FILE='mysql-bin.000950',MASTER_LOG_POS=4;

Query OK, 0 rows affected (0.09 sec)

就是在mysql上重新指定新的binlog和它的初始位置。然后启动slave：mysql> start slave;

观察slave启动正常了mysql> show slave status\G

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

Slave_IO_State: Waiting for master to send event

Master_Host: 10.90.13.238

Master_User: slave

Master_Port: 3306

Connect_Retry: 60

Master_Log_File: mysql-bin.000950

Read_Master_Log_Pos: 336968550

Relay_Log_File: mysql-relay-bin.000002

Relay_Log_Pos: 52752780

Relay_Master_Log_File: mysql-bin.000950

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: 52752634

Relay_Log_Space: 336968852

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: 31164

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: 4

1 row in set (0.00 sec)

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