Recently, we had an edge case where a MySQL slave went out-of-sync but it couldn’t be rebuilt from scratch. The slave was acting as a master server to some applications and it had data was being written to it. It was a design error, and this is not recommended, but it happened. So how do you synchronize the data in this circumstance? This blog post describes the steps taken to recover from this situation. The tools used to recover the slave were pt-slave-restart, pt-table-checksum, pt-table-sync and mysqldiff.
To illustrate this …[Read more]