解決Mysql複製Relay log read failure 的問題

1、問題描述

Mysql主從複製模式中，slave上報錯 「relay log read failure」，致使主從同步中止。

mysql> show slave status\G

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

               Slave_IO_State:

                  Master_Host: 10.0.0.93

                  Master_User: slaveuser

                  Master_Port: 3306

                Connect_Retry: 60

              Master_Log_File: dd-bin.002542

          Read_Master_Log_Pos: 752973519

               Relay_Log_File: dd-relay.002949

                Relay_Log_Pos: 950583160

        Relay_Master_Log_File: dd-bin.002540

             Slave_IO_Running: Yes

            Slave_SQL_Running: No

              Replicate_Do_DB:

          Replicate_Ignore_DB: mysql,test,information_schema

           Replicate_Do_Table:

       Replicate_Ignore_Table:

      Replicate_Wild_Do_Table:

  Replicate_Wild_Ignore_Table:

                   Last_Errno: 1594

                   Last_Error: Relay log read failure: Could not parse relay log event entry. The possible reasons are: the master's binary log is corrupted (you can check this by running 'mysqlbinlog' on the binary log), the slave's relay log is corrupted (you can check this by running 'mysqlbinlog' on the relay log), a network problem, or a bug in the master's or slave's MySQL code. If you want to check the master's binary log or slave's relay log, you will be able to know their names by issuing 'SHOW SLAVE STATUS' on this slave.

                 Skip_Counter: 0

          Exec_Master_Log_Pos: 950583017

              Relay_Log_Space: 2900478067

              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: Relay log read failure: Could not parse relay log event entry. The possible reasons are: the master's binary log is corrupted (you can check this by running 'mysqlbinlog' on the binary log), the slave's relay log is corrupted (you can check this by running 'mysqlbinlog' on the relay log), a network problem, or a bug in the master's or slave's MySQL code. If you want to check the master's binary log or slave's relay log, you will be able to know their names by issuing 'SHOW SLAVE STATUS' on this slave.

  Replicate_Ignore_Server_Ids:

             Master_Server_Id: 93

1 row in set (0.00 sec)

=============================================

2、緣由分析

      報錯信息爲從庫「沒法讀取relay log 裏的條目」，可能緣由爲master庫的binglog錯誤，或slave庫的中繼日誌錯誤。或者爲網絡問題及bug緣由。

      通常是因爲網絡故障或slave庫壓力過大，致使relay-log格式錯誤形成的。找到當前已經同步的時間點，從新設置主從同步，就會產生新的中繼日誌，恢復正常。

3、問題處理

從"show  slave  status\G"的輸出中，找到以下信息：

Relay_Master_Log_File: dd-bin.002540     //slave庫已讀取的master的binlog

Exec_Master_Log_Pos: 950583017           //在slave上已經執行的position位置點

    停掉slave，以slave已經讀取的binlog文件，和已經執行的position爲起點，從新設置同步。會產生新的中繼日誌，問題解決。

（不須要指定host，user，password等，默認使用當前已經設置好的）

mysql>stop slave; mysql>change master to master_log_file='dd-bin.002540' , master_log_pos=950583017; mysql>start slave;

4、驗證結果

再次查看，錯誤已經解決，slave 開始追 master 的日誌

mysql>show  slave status\G

Exec_Master_Log_Pos: 225927489        //slave上已經執行的position已經變化

Seconds_Behind_Master: 58527            //slave  落後主庫的時間，單位秒

過幾秒鐘，再次查看。離與master同步更近了

mysql>show  slave status\G

Exec_Master_Log_Pos: 307469867

Seconds_Behind_Master: 29570

5、從relay-log中驗證最後同步日誌position。（做爲驗證，非必須）

還能夠從  Relay_Log_File: dd-relay.002949  的記錄找到當前已經同步的position。

使用mysqlbinlog 查看中繼日誌 dd-relay.002949 最後的記錄

#mysqlbinlog  dd-relay.002949 >/tmp/relay_log.sql #tail   /tmp/relay_log.sql # at 950582947 #140914 3:32:30 server id 93 end_log_pos 950582990 Query thread_id=1256813 exec_time=0 error_code=0 SET TIMESTAMP=1410636750/*!*/; insert into blog_month_post_count (id, `count`) values (34509691, 0) on duplicate key update `count`=values(`count`) /*!*/; # at 950583133 #140914 3:32:30 server id 93 end_log_pos 950583017 Xid = 14033635514 COMMIT/*!*/; # at 950583160 #140914 3:32:30 server id 93 end_log_pos 950583092 Query thread_id=1256815 exec_time=0 error_code=0 SET TIMESTAMP=1410636750/*!*/; BEGIN /*!*/; DELIMITER ; # End of log file ROLLBACK /* added by mysqlbinlog */; /*!50003 SET COMPLETION_TYPE=@OLD_COMPLETION_TYPE*/;

能夠看到，中繼日誌中最後一次執行成功的position 爲 950583017，與 Exec_Master_Log_Pos: 950583017 記錄一致。