When learning ProxySQL, we have seen some confusion around the configuration and especially around the usage of the configuration file. In this post, we will explain how ProxySQL treats its internal configuration and its configuration file.

The Proxysql.Cnf

For the initial startup, the configuration is loaded from the /etc/proxysql.cnf file. At this time, the configuration file will be parsed and the settings will be stored in the embedded SQLite database. From this point onwards, the settings will be accessed from the SQLite database.

However, there are four configuration settings which are always parsed from the config file, even when the SQLite database is present. This places a requirement for the configuration file to always be in the place, if missing, ProxySQL terminates.

• datadir: The path of ProxySQL datadir which stores database file, logs.
• restart_on_missing_heartbeats (new in 1.4.4): If MySQL threads miss restart_on_missing_heartbeats (number of) heartbeats, proxysql will raise a SIGABRT signal and restart. Default is 10.
• execute_on_exit_failure (new in 1.4.4): If set, ProxySQL’s parent process will execute the defined script every time ProxySQL crashes. It is recommended to use this setting to generate an alert or log the event. 
• errorlog (new in 2.0.0): The file to be used as error-log. Defaults to ${datadir}/proxysql.log