Accessing the MariaDB slow query and general logs - Amazon Relational Database Service

Accessing the MariaDB slow query and general logs

You can write the MariaDB slow query log and general log to a file or database table by setting parameters in your DB parameter group. For information about creating and modifying a DB parameter group, see Parameter groups for Amazon RDS. You must set these parameters before you can view the slow query log or general log in the Amazon RDS console or by using the Amazon RDS API, AWS CLI, or AWS SDKs.

You can control MariaDB logging by using the parameters in this list:

  • slow_query_log or log_slow_query: To create the slow query log, set to 1. The default is 0.

  • general_log: To create the general log, set to 1. The default is 0.

  • long_query_time or log_slow_query_time: To prevent fast-running queries from being logged in the slow query log, specify a value for the shortest query run time to be logged, in seconds. The default is 10 seconds; the minimum is 0. If log_output = FILE, you can specify a floating point value that goes to microsecond resolution. If log_output = TABLE, you must specify an integer value with second resolution. Only queries whose run time exceeds the long_query_time or log_slow_query_time value are logged. For example, setting long_query_time or log_slow_query_time to 0.1 prevents any query that runs for less than 100 milliseconds from being logged.

  • log_queries_not_using_indexes: To log all queries that do not use an index to the slow query log, set this parameter to 1. The default is 0. Queries that do not use an index are logged even if their run time is less than the value of the long_query_time parameter.

  • log_output option: You can specify one of the following options for the log_output parameter:

    • TABLE (default)– Write general queries to the mysql.general_log table, and slow queries to the mysql.slow_log table.

    • FILE– Write both general and slow query logs to the file system. Log files are rotated hourly.

    • NONE– Disable logging.

When logging is enabled, Amazon RDS rotates table logs or deletes log files at regular intervals. This measure is a precaution to reduce the possibility of a large log file either blocking database use or affecting performance. FILE and TABLE logging approach rotation and deletion as follows:

  • When FILE logging is enabled, log files are examined every hour and log files older than 24 hours are deleted. In some cases, the remaining combined log file size after the deletion might exceed the threshold of 2 percent of a DB instance's allocated space. In these cases, the largest log files are deleted until the log file size no longer exceeds the threshold.

  • When TABLE logging is enabled, in some cases log tables are rotated every 24 hours. This rotation occurs if the space used by the table logs is more than 20 percent of the allocated storage space. It also occurs if the size of all logs combined is greater than 10 GB. If the amount of space used for a DB instance is greater than 90 percent of the DB instance's allocated storage space, the thresholds for log rotation are reduced. Log tables are then rotated if the space used by the table logs is more than 10 percent of the allocated storage space. They're also rotated if the size of all logs combined is greater than 5 GB.

    When log tables are rotated, the current log table is copied to a backup log table and the entries in the current log table are removed. If the backup log table already exists, then it is deleted before the current log table is copied to the backup. You can query the backup log table if needed. The backup log table for the mysql.general_log table is named mysql.general_log_backup. The backup log table for the mysql.slow_log table is named mysql.slow_log_backup.

    You can rotate the mysql.general_log table by calling the mysql.rds_rotate_general_log procedure. You can rotate the mysql.slow_log table by calling the mysql.rds_rotate_slow_log procedure.

    Table logs are rotated during a database version upgrade.

Amazon RDS records both TABLE and FILE log rotation in an Amazon RDS event and sends you a notification.

To work with the logs from the Amazon RDS console, Amazon RDS API, Amazon RDS CLI, or AWS SDKs, set the log_output parameter to FILE. Like the MariaDB error log, these log files are rotated hourly. The log files that were generated during the previous 24 hours are retained.

For more information about the slow query and general logs, go to the following topics in the MariaDB documentation: