MySQL 8.0 Release Notes
MySQL 8.0 Source Code Documentation
This section describes the characteristics of individual error log components. For general information about configuring error logging, see Section 5.4.2, “The Error Log”.
A log component can be a filter or a sink:
A filter processes log events, to add, remove, or modify event fields, or to delete events entirely. The resulting events pass to the next log component named in the
log_error_servicessystem variable value.A sink is a destination (writer) for log events. Typically, a sink processes log events into log messages that have a particular format and writes these messages to its associated output, such as a file or the system log.
The server executes filters and sinks in the
log_error_services value in the
order they are named. The rightmost component should therefore be
a sink. If the rightmost component is a filter, any changes it has
on events have no effect on output.
The following sections describe individual log components, grouped by component type:
Component descriptions include these types of information:
The component name and intended purpose.
Whether the component is built in or must be loaded. For a loadable component, the description specifies the URN to use to load and unload the component with the
INSTALL COMPONENTandUNINSTALL COMPONENTstatements.Whether the component can be listed multiple times in the
log_error_servicesvalue.For a sink component, the destination to which the component writes output.
Error log filter components implement filtering of error log events:
If no filter component is enabled, no filtering occurs.
Any enabled filter component affects log events only for components listed later in the
log_error_servicesvalue. In particular, for any log sink component listed inlog_error_servicesearlier than any filter component, no log event filtering occurs.
The log_filter_internal Component
Purpose: Implements filtering based on log event priority and error code, in combination with the
log_error_verbosityandlog_error_suppression_listsystem variables. See Section 5.4.2.4, “Priority-Based Error Log Filtering (log_filter_internal)”.URN: This component is built in and need not be loaded with
INSTALL COMPONENTbefore use.Multiple uses permitted: No.
If log_filter_internal is disabled,
log_error_verbosity and
log_error_suppression_list have
no effect.
The log_filter_dragnet Component
Purpose: Implements filtering based on the rules defined by the
dragnet.log_error_filter_rulessystem variable setting. See Section 5.4.2.5, “Rule-Based Error Log Filtering (log_filter_dragnet)”.URN:
file://component_log_filter_dragnetMultiple uses permitted: No.
Error log sink components are writers that implement error log output. If no sink component is enabled, no log output occurs.
Some sink component descriptions refer to the default error log
destination. This is the console or a file and is indicated by
the fault of the log_error
system variable, determined as described in
Section 5.4.2.2, “Default Error Log Destination Configuration”.
The log_sink_internal Component
Purpose: Implements traditional error log message output format.
URN: This component is built in and need not be loaded with
INSTALL COMPONENTbefore use.Multiple uses permitted: No.
Output destination: Writes to the default error log destination.
The log_sink_json Component
Purpose: Implements JSON-format error logging. See Section 5.4.2.6, “Error Logging in JSON Format”.
URN:
file://component_log_sink_jsonMultiple uses permitted: Yes.
Output destination: The JSON log writer determines its output destination based on the default error log destination, which is given by the
log_errorsystem variable:If
log_errornames a file, the JSON writer bases output file naming on that file name, plus a numbered.suffix, withNN.jsonNNstarting at 00. For example, iflog_errorisfile_name, successive instances oflog_sink_jsonnamed in thelog_error_servicesvalue write tofile_name.00.jsonfile_name.01.jsonIf
log_errorisstderr, the JSON writer writes to the console. Iflog_json_writeris named multiple times in thelog_error_servicesvalue, they all write to the console, which is likely not useful.
The log_sink_syseventlog Component
Purpose: Implements error logging to the system log. This is the Event Log on Windows, and
syslogon Unix and Unix-like systems. See Section 5.4.2.7, “Error Logging to the System Log”.URN:
file://component_log_sink_syseventlogMultiple uses permitted: No.
Output destination: Writes to the system log. Does not use the default error log destination.
The log_sink_test Component
Purpose: Intended for internal use in writing test cases. Not intended for production use.
URN:
file://component_log_sink_testMultiple uses permitted: Yes.
Output destination: Writes to the default error log destination.