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mysql-error 1236

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:

http://www.brianklug.com/w/page/15052161/MySQL%20Error%3A%20Client%20requested%20master%20to%20start%20replication%20from%20impossible%20position

http://blog.ez2learn.com/2011/11/28/mysql-1236-solution/

http://blog.longwin.com.tw/2013/09/mysql-replication-error-1236-fix-2013/


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)

mysql>



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mysql-error 1236