Before you perform any mysqldump to fully restore a Slave, you should consult the output of SHOW SLAVE STATUS\G
. Let's start with a sample SHOW SLAVE STATUS\G
:
mysql> show slave status\G
*************************** 1. row ***************************
Slave_IO_State: Waiting for master to send event
Master_Host: 10.48.20.253
Master_User: replicant
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: mysql-bin.000254
Read_Master_Log_Pos: 858190247
Relay_Log_File: relay-bin.066069
Relay_Log_Pos: 873918
Relay_Master_Log_File: mysql-bin.000254
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: 858190247
Relay_Log_Space: 873772
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: 0
1 row in set (0.00 sec)
Please notice that there are two sets of replication coordinates from the Master
- (Master_Log_File,Read_Master_Log_Pos)
- (Relay_Master_Log_File,Exec_Master_Log_Pos)
There is a major difference between them
(Master_Log_File,Read_Master_Log_Pos)
tells you the last binlog statement from the Master's log file and log position that the Slave read from the Master and placed in its Relay Logs.
(Relay_Master_Log_File,Exec_Master_Log_Pos)
tells you the last binlog statement from the Master's log file and log position that the Slave read from the Master and placed in its Relay Logs THAT IS NEXT TO BE EXECUTED ON THE SLAVE.
The timestamps from these two coordinates helps you figure out Seconds_Behind_Master
.
Knowing these things, here is what you can do:
- Step 01) Run
SHOW SLAVE STATUS\G
- Step 02) Get Relay_Master_Log_File,Exec_Master_Log_Pos from
SHOW SLAVE STATUS\G
(In the sample, that would be (mysql-bin.000254,858190247)
- Step 03)
STOP SLAVE;
- Step 04)
CHANGE MASTER TO master_log_file='mysql-bin.000254',master_log_pos=858190247;
- Step 05)
START SLAVE;
- Step 06) Wait 10 seconds
- Step 07) Run
SHOW SLAVE STATUS\G
and check Seconds_Behind_Master
If the Seconds_Behind_Master
is a number and eventaully drops to zero, replication is fully reesatablished.
After doing all this, if replication breaks because of a corrupt binary log from the master, then you do the last resort:
- Steo 01) On the Master,
RESET MASTER;
to erase all binary logs and start with a new one
- Step 02) On the Master, run this
This create proper dump for the slave
echo "STOP SLAVE;" > /root/MySQLData.sql
mysqldump --all-databases --routines --triggers --flush-privileges --master-data=1 >> /root/MySQLData.sql
echo "START SLAVE;" >> /root/MySQLData.sql
- Step 03) scp /root/MySQLData.sql over to the Slave and Load it in MySQL on the Slave
Give it a Try !!!