MariaDB Error Log Configuration

MariaDB® logs include the following types:

• Error log: This log is always enabled, logging all critical errors. It can also log warnings.

• General query log: The --general-log variable enables this log. You can debug and audit queries by enabling it.

• Slow query log: Enable this log by starting mysqld with option --slow-query-log. You can identify queries that cause performance issues by enabling this log.

• Binary log: Enable this log by starting mysqld with option --log-bin. This log is for replication masters only.

You can customize the log configuration of MariaDB by using system variables.

The error log

You can find error logs in the datadir directory. By default, the system names the error logs as ${hostname}.err. The log_error system variable changes the default name and writes logs to the datadir directory.

You can change the absolute path of the error logs by adding the path to the name, as shown in the following example:

[mariadb]
...
log_error=/var/log/mysql/mariadb.err

You can configure the prefix of the log files with the log-basename variable. The prefix applies to all log files, such as error logs, general query logs, slow query logs, binary logs, and so on. Error logs have the .err extension.

Send error logs to stderr

In Unix® and Unix-like environments, you don't set the log_error variable, and stderr (the terminal window where you ran mysqld) displays errors by default. If stderr doesn't display errors, unset the log_error variable
with the --skip-log-error option.

Error log verbosity

Use the log_warnings system variable to configure the verbosity of error logs:

[mariadb]
...
log_warnings=3

The warnings can have the following verbosity levels:

• Level 0 logs some core warnings but ignores many optional warnings.

• Level 1 logs the following warnings, among others:

  • Replication-related messages.
  • DNS-lookup failure messages.
  • Event scheduler messages.
  • Unsafe statements for statement-based replication messages.

• Level 2 logs the following warnings, among others:

  • Access-denied errors.
  • Aborted connections due to timeouts.
  • Table-handler errors.

• Level 3 logs the following warnings, among others:

  • Old-style language options messages.
  • Progress of InnoDB online DDL-related messages.

• Level 4 logs the following warnings, among others:

  • Killed connections messages.
  • All closed connections messages.
  • Released connections messages.

• Level 9 logs the following warning, among others:

  • Initializing plugins messages.

Refer to the MariaDB documentation for more information about system variables configuration and error logs.

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