一、问题描述

Mysql主从复制模式中，slave上报错 “relay log read failure”，导致主从同步停止。

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
mysql> show slave status\G
*************************** 1. row ***************************
               Slave_IO_State: Queueing master event to the relay log
                  Master_Host: 192.168.99.44
                  Master_User: repl
                  Master_Port: 3306
                Connect_Retry: 30
              Master_Log_File: binlog44-master.003604
          Read_Master_Log_Pos: 432257567
               Relay_Log_File: mysql-45relay-bin.010722
                Relay_Log_Pos: 323173998
        Relay_Master_Log_File: binlog44-master.003575
             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: 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: 323173781
              Relay_Log_Space: 16005431524
              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: 44
                  Master_UUID: beac8e0e-4c65-11ec-9cb1-0050568efcb0
             Master_Info_File: /var/lib/mysql/master.info
                    SQL_Delay: 0
          SQL_Remaining_Delay: NULL
      Slave_SQL_Running_State:
           Master_Retry_Count: 86400
                  Master_Bind:
      Last_IO_Error_Timestamp:
     Last_SQL_Error_Timestamp: 220127 13:49:03
               Master_SSL_Crl:
           Master_SSL_Crlpath:
           Retrieved_Gtid_Set:
            Executed_Gtid_Set:
                Auto_Position: 0
         Replicate_Rewrite_DB:
                 Channel_Name:
           Master_TLS_Version:
1 row in set (0.85 sec)

二、原因分析

1
2
3
报错信息为从库“无法读取relay log 里的条目”，可能原因为master库的binglog错误，或slave库的中继日志错误。或者为网络问题及bug原因。

一般是由于网络故障或slave库压力过大，导致relay-log格式错误造成的。找到当前已经同步的时间点，重新设置主从同步，就会产生新的中继日志，恢复正常。

三、问题处理

从”show slave status\G”的输出中，找到如下信息：

1
2
Relay_Master_Log_File: binlog44-master.003575     //slave库已读取的master的binlog
Exec_Master_Log_Pos: 323173781           //在slave上已经执行的position位置点

停掉slave，以slave已经读取的binlog文件，和已经执行的position为起点，重新设置同步。会产生新的中继日志，问题解决。

（不需要指定host，user，password等，默认使用当前已经设置好的）

1
2
3
4
5
mysql>stop slave;

mysql>change master to master_log_file='binlog44-master.003575' , master_log_pos=323173781;

mysql>start slave;

四、验证结果

再次查看，错误已经解决，slave 开始追 master 的日志

1
2
3
mysql>show  slave status\G
Exec_Master_Log_Pos: 225927489        //slave上已经执行的position已经变化
Seconds_Behind_Master: 58527            //slave  落后主库的时间，单位秒

过几秒钟，再次查看。离与master同步更近了

1
2
3
4
5
mysql>show  slave status\G

Exec_Master_Log_Pos: 307469867

Seconds_Behind_Master: 29570