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Checking and repairing mysql replication automatically.


MySQL replication has been known to easily break, as a result of a large multitude of potential causes.

Sometimes the replication can even break if an erroneous query is executed on the master server.

With all the potential issues that may break replication, we thought it prudent to write an automated check script that can run on a scheduled basis (i.e. every 10-15 minutes), check the Slave status, report on any errors if applicable and attempt to repair replication.

We have built this script to exit and send mail alerts if any step of the checking and repairing process fails or generates an error in itself.

The script also generates a lock file to ensure that no more than one check process can run at any given time. We feel this script could be best used for scenarios for remote MySQL slaves, for example. Adding this extra layer may ensure a more reliable replication.

The repair process is simply 3 MySQL Commands :

The above directives assume that you have a master.info with the mysql master server information statically set. No CHANGE MASTER commands have to be executed as a result. Resetting the slave clears the error and resumes replication, and all the queries missed during the time it failed should be queued and applied after it starts again.

Here is the script :