Slow query log rotation and expiration

Important

This feature is a tech preview. Before using this feature in production, we recommend that you test restoring production from physical backups in your environment, and also use the alternative backup method for redundancy.

This feature was implemented in Percona Server for MySQL 8.0.27-18.

Percona has implemented two new variables, max_slowlog_size and max_slowlog_files to provide users with ability to control the slow query log disk usage. These variables have the same behavior as the max_binlog_size variable and the max_binlog_files variable used for controlling the binary log.

System variables

max_slowlog_size

Option	Description
Command-line	Yes
Config file	Yes
Scope	Global
Dynamic	Yes
Data type	numeric
Default	0 (unlimited)
Range	0 - 1073741824

The max_slowlog_size variable controls when the server rotates the slow query log file based on size.

The value is set to 0 by default, which means the server does not automatically rotate the slow query log file.

The block size is 4096 bytes. If you set a value that is not a multiple of 4096, the server rounds it down to the nearest multiple of 4096. For example, setting max_slowlog_size to any value less than 4096 will effectively set the value to 0.

If you set a limit for this size and enable this feature, the server will rename the slow query log file to slow_query_log_file.000001 once it reaches the specified size.

max_slowlog_files

Option	Description
Command-line	Yes
Config file	Yes
Scope	Global
Dynamic	Yes
Data type	numeric
Default	0 (unlimited)
Range	0 - 102400

This variable limits the total amount of slow query log files and is used with max_slowlog_size.

The server creates and adds slow query logs until it reaches the range’s upper value. When the upper value is reached, the server creates a new slow query log file with a higher sequence number and deletes the log file with the lowest sequence number, maintaining the total amount defined in the range.