The Error Log • syseventlog.include_pid : Whether to include the server process ID in each line of  syslog  output. • syseventlog.tag : This variable defines a tag to add to the server identifier ( mysqld ) in  syslog messages. If defined, the tag is appended to the identifier with a leading hyphen. Note Prior to MySQL 8.0.13, use the  log_syslog_facility , log_syslog_include_pid , and  log_syslog_tag  system variables rather than the  syseventlog. xxx  variables. MySQL uses the custom label “System”  for important system messages about non-error situations, such as startup, shutdown, and some significant changes to settings. In logs that do not support custom labels, including the Event Log on Windows, and  syslog  on Unix and Unix-like systems, system messages are assigned the label used for the information priority level. However, these messages are printed to the log even if the MySQL  log_error_verbosity  setting normally excludes messages at the information level. When a log sink must fall back to a label of “Information”  instead of “System”  in this way, and the log event is further processed outside of the MySQL server (for example, filtered or forwarded by a  syslog configuration), these events may by default be processed by the secondary application as being of “Information”  priority rather than “System”  priority. Each error log sink (writer) component has a characteristic output format it uses to write messages to its destination, but other factors may influence the content of the messages: For names and descriptions of the fields in error events, see Section 5.4.2.3, “Error Event Fields” . For all log sinks, the thread ID included in error log messages is that of the thread within  mysqld  responsible for writing the message. This ID indicates which part of the server produced the message, and is consistent with general query log and slow query log messages, which include the connection thread ID. The internal log sink produces traditional error log output. For example: 1042 2020-08-06T14:25:02.835618Z 0 [Note] [MY-012487] [InnoDB] DDL log recovery : begin 2020-08-06T14:25:02.936146Z 2020-08-06T14:25:02.963127Z 0 [Note] [MY-010253] [Server] IPv6 is available. 2020-08-06T14:25:03.109022Z log_sink_internal Output Format •System Variables That Affect Error Log Format •Early-Startup Logging Output Format •log_sink_syseventlog Output Format •log_sink_json Output Format •log_sink_internal Output Format •System variables may affect log sinks. See System Variables That Affect Error Log Format. •The information relevant to the log sink. Not every sink writes all fields available in error events. •The information available to the log sink. If a log filter component executed prior to execution of the sink component removes a log event field, that field is not available for writing. For information about log filtering, see Section 5.4.2.4, “Types of Error Log Filtering” . 5.4.2.9 Error Log Output Format