ProxySQL is a high performance, high availability, protocol aware proxy for MySQL and forks (like Percona Server and MariaDB). All the while getting the unlimited freedom that comes with a GPL license.
Its development is driven by the lack of open source proxies that provide high performance.
Source: sysown/proxysql: High-performance MySQL proxy with a GPL license.
There are two models of load balancing: transport and application layer. HAProxy is a great TCP load balancer, but it’s lack of SQL awareness effectively limits its ability to address certain scaling issues in distributed database environments. In the open source world, there’s been a few SQL-aware load balancers, namely MySQL Proxy, ProxySQL and MaxScale, but they all seemed to be in beta status and unfit for production use. So we were pretty excited when the MariaDB team released a GA version of MaxScale earlier this year. In this blog, we’ll have a look at MaxScale and see how it compares with HAProxy.
מקור: How to Deploy and Configure MaxScale for SQL Load Balancing with Read-Write Split | Severalnines
A load balancer heartbeat / health checker url, and also a configurable nagios compliant cron health checker. This should out of the box with most load balancers, eg Amazon ELB, F5, HA proxy etc as most of these simply check the http status for 200 or non-200 response codes.