mysql slave requested master to start replication from position greater than the file size

If you happen to reset your master mysql server without shutting down the mysql process (probably because of your super collocation cut the power!!!) you could have a slave server, which have the following error:

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 position > file size; the first event 'mysql-bin.005173' at 644642725, the last event read from './mysql-bin.005173' at 4, the last byte read from './mysql-bin.005173' at 4.'

The slave server wants to read a position in the master, which does not exist probably because it was not committed to the file.

It is fairly easy (and in most cases safe) to just correct the position and restart the replication! Take the Master_Log_File and Read_Master_Log_Pos on the slave with:

[root@mysql1 ~]# mysql
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 50497
Server version: 5.6.38-log MySQL Community Server (GPL)

Copyright (c) 2000, 2017, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> show slave status\G;
*************************** 1. row ***************************
               Slave_IO_State: 
                  Master_Host: 10.10.10.10
                  Master_User: replusr
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: mysql-bin.005173
          Read_Master_Log_Pos: 644642725
               Relay_Log_File: mysqld-relay-bin.000479
                Relay_Log_Pos: 644642888
        Relay_Master_Log_File: mysql-bin.005173
             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: 0
          Exec_Master_Log_Pos: 644642725
              Relay_Log_Space: 644643109
              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 position > file size; the first event 'mysql-bin.005173' at 644642725, the last event read from './mysql-bin.005173' at 4, the last byte read from './mysql-bin.005173' at 4.'
               Last_SQL_Errno: 0
               Last_SQL_Error: 
  Replicate_Ignore_Server_Ids: 
             Master_Server_Id: 2
                  Master_UUID: ce8a6c29-cf8e-11e5-9d39-000000000001
             Master_Info_File: /var/lib/mysql/master.info
                    SQL_Delay: 0
          SQL_Remaining_Delay: NULL
      Slave_SQL_Running_State: Slave has read all relay log; waiting for the slave I/O thread to update it
           Master_Retry_Count: 86400
                  Master_Bind: 
      Last_IO_Error_Timestamp: 180525 16:27:22
     Last_SQL_Error_Timestamp: 
               Master_SSL_Crl: 
           Master_SSL_Crlpath: 
           Retrieved_Gtid_Set: 
            Executed_Gtid_Set: 
                Auto_Position: 0
1 row in set (0.00 sec)

As you can see the highlighted variables are important, that is the file and the position you should check in your master mysql server. So go to your master datadir (or the binlog directory, which could be changed with “binlog-dir”) and check whether there is Master_Log_File: “mysql-bin.005173” with position Read_Master_Log_Pos: “644642725”

srv@local-master ~ # cd /var/lib/mysql/
srv@local-master mysql # ls -altr mysql-bin.005173
-rw-rw---- 1 mysql mysql 644639026 24 may 12,22 mysql-bin.005173
srv@local-master mysql # mysqlbinlog mysql-bin.005173|tail -n 15
# at 644638722
#180524 12:03:31 server id 2  end_log_pos 644638930 CRC32 0xfeabe1ab    Query   thread_id=88263388      exec_time=0     error_code=0
SET TIMESTAMP=1527152611/*!*/;
UPDATE `group_desc` SET `id` = '153357',`name` = 'Test Group Name',`tags` = '|Test Group |' WHERE  `id` = '153357'
/*!*/;
# at 644638930
#180524 12:03:31 server id 2  end_log_pos 644639026 CRC32 0x5ca1b693    Query   thread_id=88263388      exec_time=0     error_code=0
SET TIMESTAMP=1527152611/*!*/;
COMMIT
/*!*/;
DELIMITER ;
# End of log file
ROLLBACK /* added by mysqlbinlog */;
/*!50003 SET COMPLETION_TYPE=@OLD_COMPLETION_TYPE*/;
/*!50530 SET @@SESSION.PSEUDO_SLAVE_MODE=0*/;
srv@local-master ~ # 

And yes, there is no position Read_Master_Log_Pos: “644642725” as the slave requested! The position number starts with

# at

for example

# at 644638930

As you can see from the bash commands above we got the last 15 lines of our binlog mysql file and the last position was 644638930. Here is what is going on: slave requested to continue from master’s position at 644642725, but master has last position 644638930:

644642725 > 644638930

To fix it just use the next binlog file and position 1 and your slave will continue normally. Let’s say there is a possibility your master missed to write the last commands to the master’s binlog because of the reset and in this situation your slave could be out of sync and in this case you should recover your slave from a full mysql dump and import in the slave. But in most cases it is fairly safe to continue.

[root@mysql1 ~]# mysql
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 50506
Server version: 5.6.38-log MySQL Community Server (GPL)

Copyright (c) 2000, 2017, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> STOP SLAVE;
Query OK, 0 rows affected (0.12 sec)

mysql> CHANGE MASTER TO MASTER_LOG_FILE='mysql-bin.005174',MASTER_LOG_POS=1;
Query OK, 0 rows affected (0.47 sec)

mysql> START SLAVE;
Query OK, 0 rows affected (0.04 sec)

And if everything is OK your slave will continue with no errors (just with a big delay – behind your master):

mysql> show slave status\G;
*************************** 1. row ***************************
               Slave_IO_State: Waiting for master to send event
                  Master_Host: 10.10.10.10
                  Master_User: replusr
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: mysql-bin.005175
          Read_Master_Log_Pos: 328685690
               Relay_Log_File: mysqld-relay-bin.000003
                Relay_Log_Pos: 36999
        Relay_Master_Log_File: mysql-bin.005175
             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: 36836
              Relay_Log_Space: 334719008
              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: 103216
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: 2
                  Master_UUID: ce8a6c29-cf8e-11e5-9d39-000000000001
             Master_Info_File: /var/lib/mysql/master.info
                    SQL_Delay: 0
          SQL_Remaining_Delay: NULL
      Slave_SQL_Running_State: Repair by sorting
           Master_Retry_Count: 86400
                  Master_Bind: 
      Last_IO_Error_Timestamp: 
     Last_SQL_Error_Timestamp: 
               Master_SSL_Crl: 
           Master_SSL_Crlpath: 
           Retrieved_Gtid_Set: 
            Executed_Gtid_Set: 
                Auto_Position: 0
1 row in set (0.00 sec)

But if you get:

Duplicate entry

Last_SQL_Errno: 1062
Last_SQL_Error: Error 'Duplicate entry '422987' for key 'PRIMARY'' on query. Default database: 'mydb'. Query: 'INSERT INTO `spec_cookie` (`userid`, `userip`, `cookie`, `added`) VALUES ('96201', '2591115382', 'f3b81be45a484c652d38a2c70f8c44c30d4d04d1293918c9071e052ffd9c76f7', NOW())'

You might get into troubles if you continue, be careful!!! Examine the query, select the data in the slave and in the master, if they are equal you can skip it the error with:

[srv@local-slave ~]# mysql
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 50506
Server version: 5.6.38-log MySQL Community Server (GPL)

Copyright (c) 2000, 2017, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> STOP SLAVE;
Query OK, 0 rows affected (0.09 sec)

mysql> SET GLOBAL SQL_SLAVE_SKIP_COUNTER=1;
Query OK, 0 rows affected (0.00 sec)

mysql> START SLAVE;
Query OK, 0 rows affected (0.12 sec)

mysql>

If they are not equal you can change them manually and continue again. More about Duplicate entry you can check here (similar mysql binlog problems): mysql slave reset and fixing relay log read failure

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