MySQL :: MySQL 8.4 Reference Manual :: 7.5.3 Error Log Components (original) (raw)

7.5.3 Error Log Components

This section describes the characteristics of individual error log components. For general information about configuring error logging, see Section 7.4.2, “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 in the list of enabled components.
• 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. A sink may also write to the Performance Schemaerror_log table; seeSection 29.12.22.2, “The error_log Table”. Events pass unmodified to the next log component in the list of enabled components (that is, although a sink formats events to produce output messages, it does not modify events as they pass internally to the next component).

The log_error_services system variable lists the enabled log components. Components not named in the list are disabled.log_error_services also implicitly loads error log components if they are not already loaded. For more information, seeSection 7.4.2.1, “Error Log Configuration”.

The following sections describe individual log components, grouped by component type:

• Filter Error Log Components
• Sink Error Log Components

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 if explicitly loading or unloading the component with theINSTALL COMPONENT andUNINSTALL COMPONENT statements. Implicitly loading error log components requires only the component name. For more information, seeSection 7.4.2.1, “Error Log Configuration”.
• Whether the component can be listed multiple times in thelog_error_services value.
• For a sink component, the destination to which the component writes output.
• For a sink component, whether it supports an interface to the Performance Schema error_log table.

Sink Error Log Components

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 value of the log_error system variable, determined as described inSection 7.4.2.2, “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.
• Multiple uses permitted: No.
• Output destination: Writes to the default error log destination.
• Performance Schema support: Writes to theerror_log table. Provides a parser for reading error log files created by previous server instances.

The log_sink_json Component

• Purpose: Implements JSON-format error logging. SeeSection 7.4.2.7, “Error Logging in JSON Format”.
• URN: file://component_log_sink_json
• Multiple uses permitted: Yes.
• Output destination: This sink determines its output destination based on the default error log destination, which is given by thelog_error system variable:
  • If log_error names a file, the sink bases output file naming on that file name, plus a numbered._`NN`_.json suffix, with NN starting at 00. For example, iflog_error is_filename_, successive instances of log_sink_json named in the log_error_services value write to_`filename`_.00.json,_`filename`_.01.json, and so forth.
  • If log_error isstderr, the sink writes to the console. If log_sink_json is named multiple times in thelog_error_services value, they all write to the console, which is likely not useful.
• Performance Schema support: Writes to theerror_log table. Provides a parser for reading error log files created by previous server instances.

The log_sink_syseventlog Component

• Purpose: Implements error logging to the system log. This is the Event Log on Windows, and syslog on Unix and Unix-like systems. SeeSection 7.4.2.8, “Error Logging to the System Log”.
• URN:file://component_log_sink_syseventlog
• Multiple uses permitted: No.
• Output destination: Writes to the system log. Does not use the default error log destination.
• Performance Schema support: Does not write to theerror_log table. Does not provide a parser for reading error log files created by previous server instances.

The log_sink_test Component

• Purpose: Intended for internal use in writing test cases, not for production use.
• URN: file://component_log_sink_test

Sink properties such as whether multiple uses are permitted and the output destination are not specified forlog_sink_test because, as mentioned, it is for internal use. As such, its behavior is subject to change at any time.