Description:
When the power is cut to a MySQL master database server, it is typically the case that when it comes back online it will have slaves that are further ahead of it (because sync_binlog defaults to zero: http://dev.mysql.com/doc/refman/5.7/en/replication-options-binary-log.html#sysvar_sync_bin... )
I was discussing this with a colleague, and we believe that the error message should be more verbose in indicating the common cause.
How to repeat:
mysql> show slave status \G
*************************** 1. row ***************************
Slave_IO_State:
Master_Host: n2i-prd2.cf2dydfxiush.us-east-1.rds.amazonaws.com
Master_User: rdsrepladmin
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: mysql-bin-changelog.226554
Read_Master_Log_Pos: 2542793
Relay_Log_File: relaylog.054194
Relay_Log_Pos: 210
Relay_Master_Log_File: mysql-bin-changelog.226554
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: 2542793
Relay_Log_Space: 141863
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-changelog.226554' at 2542793, the last event read from '/rdsdbdata/log/binlog/mysql-bin-changelog.226554' at 4, the last byte read from '/rdsdbdata/log/binlog/mysql-bin-changelog.226554' at 4.'
Last_SQL_Errno: 0
Last_SQL_Error:
Replicate_Ignore_Server_Ids:
Master_Server_Id: 1566631948
Suggested fix:
Could be:
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-changelog.226554' at 2542793, the last event read from '/rdsdbdata/log/binlog/mysql-bin-changelog.226554' at 4, the last byte read from '/rdsdbdata/log/binlog/mysql-bin-changelog.226554' at 4. Possible causes for this include a master server which recently crashed and did not have sync_binlog=1 enabled - leading to data loss on the master, which the slave has already applied.
