MySQL5.1主从同步出现Relay log read failure错误解决方法
众所周知MySQL5.1的Replication是比较烂的。MySQL的每一个版本更新关于同步方面每次都是可以看到一大堆。但MySQL5.1性能是比较突出的。所以经不住诱惑使用MySQL5.1。所以也要经常遇到一些Bug。如：
mysql>showslavestatus\G
***************************1.row***************************
Slave_IO_State:Waitingformastertosendevent
Master_Host:192.168.10.118
Master_User:repl_wu
Master_Port:3306
Connect_Retry:30
Master_Log_File:mysql-bin.005121
Read_Master_Log_Pos:64337286
Relay_Log_File:relay-bin.003995
Relay_Log_Pos:18446697137031827760
Relay_Master_Log_File:mysql-bin.005121
Slave_IO_Running:Yes
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:1594
Last_Error:Relaylogreadfailure:Couldnotparserelaylogevententry.Thepossiblereasonsare:themaster'sbinarylogiscorrupted(youcancheckthisbyrunning'mysqlbinlog'onthebinarylog),theslave'srelaylogiscorrupted(youcancheckthisbyrunning'mysqlbinlog'ontherelaylog),anetworkproblem,orabuginthemaster'sorslave'sMySQLcode.Ifyouwanttocheckthemaster'sbinarylogorslave'srelaylog,youwillbeabletoknowtheirnamesbyissuing'SHOWSLAVESTATUS'onthisslave.
Skip_Counter:0
Exec_Master_Log_Pos:4
Relay_Log_Space:64337901
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:1594
Last_SQL_Error:Relaylogreadfailure:Couldnotparserelaylogevententry.Thepossiblereasonsare:themaster'sbinarylogiscorrupted(youcancheckthisbyrunning'mysqlbinlog'onthebinarylog),theslave'srelaylogiscorrupted(youcancheckthisbyrunning'mysqlbinlog'ontherelaylog),anetworkproblem,orabuginthemaster'sorslave'sMySQLcode.Ifyouwanttocheckthemaster'sbinarylogorslave'srelaylog,youwillbeabletoknowtheirnamesbyissuing'SHOWSLAVESTATUS'onthisslave.
1rowinset(0.00sec)
从上面可以看到是中继日值或是Master上的日值出问题了。
首先如果是中继日值坏掉，那只需要找到同步的时间点，然后重新同步，这样就可以有新的中继日值了。如果Master上的日值坏了就麻烦了。
从经验来看，这是中继日值出问题了。处理方法：
需要找到同步的点。
日值为：Master_Log_File:mysql-bin.005121，Relay_Master_Log_File:mysql-bin.005121以Relay_Master_Log_File为准，Master_Log_File为参考。
日值执行时间点：
Exec_Master_Log_Pos:4
那么现在就可以：
mysql>stopslave; mysql>changemastertoMaster_Log_File='mysql-bin.005121',Master_Log_Pos=4; mysql>startslave; mysql>showslavestatus\G;
进行确认。
建议：
在使用MySQL-5.1.36以下的版本的同学，请尽快升级到MySQL-5.1.40&MySQL-5.1.37sp1