Error messages are also handled by plugins. Drizzle loads the Error Messages to STDERR plugin by default which prints error messages to STDERR. In many cases, this is sufficient if STDERR is redirected to a log file when starting Drizzle.
Note that beginning with the first Drizzle 7.1 Beta 2011.10.28 drizzled will also log messages via syslog and this is in addition to using STDOUT and STDERR. This functionality is provided by the Syslog plugin. (For example on Ubuntu these messages are written to /var/log/syslog).
The Query Log plugin is the most feature-complete and flexible query logging plugin. It logs queries to a file with a consistent, easy-to-parse format, and all of its options are dynamic, so once the plugin is loaded, logging can be enabled and disabled at runtime.
Drizzle does not load the Query Log plugin by default, so you must load it when starting Drizzle.
The Syslog plugin also provides basic query logging to the system log. Although the plugin is loaded by default, you must enable query logging by specifying --syslog.logging-enable and one of the threshold options, such as --syslog.logging-threshold-slow. The plugin is not dynamic, so once query logging is enabled, you must restart Drizzle to disable or change its settings.