ProxySQL

This package implements freno store support for ProxySQL

Logic

Freno will probe servers found in the stats.stats_mysql_connection_pool ProxySQL admin table that have either status:

1. ONLINE - connect, ping and replication checks pass
2. SHUNNED_REPLICATION_LAG - connect and ping checks pass, but replication is lagging

All other statuses are considered unhealthy and therefore are ignored by freno, eg:

1. SHUNNED - proxysql connot connect and/or ping a backend
2. OFFLINE_SOFT - a server that is draining, usually for maintenance, etc
3. OFFLINE_HARD - a server that is completely offline

Requirements

1. The ProxySQL admin port is reachable to Freno
2. The ProxySQL global variable admin-stats_credentials is defined
   • ProxySQLUser in MySQLConfigurationSettings (global) or User in ProxySQLConfigurationSettings (per-cluster) must be equal to admin-stats_credentials
   • ProxySQLPassword in MySQLConfigurationSettings (global) or Password in ProxySQLConfigurationSettings (per-cluster) must be equal to admin-stats_credentials
3. The ProxySQL monitor module is enabled, eg: mysql-monitor_enabled is true
   • The ProxySQL --no-monitor daemon flag cannot be set
4. The max_replication_lag column is defined for backend servers in the mysql_servers admin table
   • This ensures reads do not receive stale data but lagging nodes are still probed