When designing a highly-available MySQL architecture, having a proxy to route the traffic to the appropriate instances is crucial to achieve transparent (or almost) failovers/switchovers. ProxySQL, a popular open source, SQL-level proxy is a great choice for this, and even though an experimental clustering feature is available, we could follow a simpler active-passive approach too, based on Common Address Redundancy Protocol (CARP), which will also provide a highly available IP for the applications to connect.

Solution overview

As mentioned before, this setup relies on a shared IP configured through CARP on the two hosts that will be running ProxySQL. CARP configuration is outside the scope of this post but the steps are on available on the FreeBSD documentation.

We then need to make sure all ProxySQL configuration changes performed on the …