Repair a broken MySQL slave
If a MySQL slave encounters an error while replicating commands from the master, the slave will abort.
One way this can happen is if you are using triggers on a table that calls a stored procedure, but the stored procedures are missing on the slave because you forgot to include the –routines option when generating a mysqldump from the master to import to the slave.
So what do you do? First, verify that the slave is indeed encountering errors:
mysql> SHOW SLAVE STATUS \G *************************** 1. row *************************** Slave_IO_State: Waiting for master to send event Master_Host: 126.96.36.199 Master_User: slave_user Master_Port: 3306 Connect_Retry: 60 Master_Log_File: mysql-bin.001079 Read_Master_Log_Pos: 269214454 Relay_Log_File: slave-relay.000130 Relay_Log_Pos: 100125935 Relay_Master_Log_File: mysql-bin.001079 Slave_IO_Running: Yes Slave_SQL_Running: No Replicate_Do_DB: mydb Replicate_Ignore_DB: Replicate_Do_Table: Replicate_Ignore_Table: Replicate_Wild_Do_Table: Replicate_Wild_Ignore_Table: Last_Errno: 1146 Last_Error: Error 'Table 'mydb.taggregate_temp_1212047760' doesn't exist' on query. Default database: 'mydb'. Query: 'UPDATE thread AS thread,taggregate_temp_1212047760 AS aggregate SET thread.views = thread.views + aggregate.views WHERE thread.threadid = aggregate.threadid' Skip_Counter: 0 Exec_Master_Log_Pos: 203015142 Relay_Log_Space: 166325247 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 1 row in set (0.00 sec) mysql>
If either Slave_IO_Running or Slave_SQL_Running are ‘No’ then the slave has aborted. Here’s how to fix it:
Stop the slave
mysql> STOP SLAVE;
Resolve the error
Pay attention to the Last_Error field and try to resolve it. If this is a recurring issue you may need to import a fresh dump from the master to bring your slave back into sync. If the situation merits it, you can run the following to have the slave skip the offending SQL query:mysql> SET GLOBAL SQL_SLAVE_SKIP_COUNTER = 1;
Be careful, though because this could have severe repercussions down the line.
Restart the slavemysql> START SLAVE;
Verify that the slave is runningmysql> SHOW SLAVE STATUS \G
When Slave_IO_Running and Slave_SQL_Running both are set to ‘Yes’ then you’re good to go. It would probably be a good idea to have some sort of monitor to ensure your slaves are indeed running when you need them to. Perhaps I’ll throw together a quick script to do that…
Thanks to http://www.howtoforge.com/how-to-repair-mysql-replication for this information.