When mysql shows Slave_IO_Running and Slave_SQL_Running is false, then there is much evidence that the current slave relay log is broken.
show slave status \G then looks for example like this:
mysql> show slave status \G
*************************** 1. row ***************************
Slave_IO_State: Waiting for master to send event
Master_Host: master.example.com
Master_User: slaver_user
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: mysql-bin.000647
Read_Master_Log_Pos: 61270084
Relay_Log_File: slave-relay.000126
Relay_Log_Pos: 52548973
Relay_Master_Log_File: mysql-bin.000647
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: 52555768
Relay_Log_Space: 61271463
Until_Condition: None
Until_Log_File:
Until_Log_Pos: 0
Master_SSL_Allowed: Yes
Master_SSL_CA_File: /etc/mysql/ssl/ca-cert.pem
Master_SSL_CA_Path:
Master_SSL_Cert:
Master_SSL_Cipher: DHE-RSA-AES256-SHA
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: 2
1 row in set (0.00 sec)
To fix the error with the current binlog zu beheben, you can set the log to the right position.Decisive are the values for Relay_Master_Log_File and Exec_Master_Log_Pos.
Relay_Master_Log_File: mysql-bin.000647
Exec_Master_Log_Pos: 52555768
To set the new position:
stop slave;
reset slave;
change master to master_log_file='mysql-bin.000647', master_log_pos=52555768;
start slave;
Note:reset slave; deletes master.info, relay-log.info and all relay log files. Manually clean up in /var/lib/mysql is recommended.