wait_timeout
INFO
Rule IDs: cn_004
Overview
- Purpose
- Documented in the MySQL 8.4 manual as a server system variable (scope: Both). Purpose and semantics are described at the linked manual page.
- Dynamic (MySQL 8.4 reference)
- MySQL 8.4 marks this variable as dynamic (
Dynamic= Yes). Runtime changes useSET GLOBAL(global scope) orSET SESSION(session scope) — confirm syntax and persistence (SET PERSIST) in the manual. - Default value
- 28800 (8 hours) (MySQL 8.4)
- Version and product notes
- MariaDB and Percona Server may use different names, defaults, or dynamic behavior; verify their documentation.
- Documentation
- https://dev.mysql.com/doc/refman/8.4/en/server-system-variables.html#sysvar_wait_timeout
- Other vendors
What is checked
Rules that reference this variable, with their severity and what each rule detects:
- INFO
cn_004: Reduce wait_timeout to 300-600s for most web applications. Connection pools handle reconnection automatically.
Tuning guidance
- Recommended actions:
- Reduce wait_timeout to 300-600s for most web applications. Connection pools handle reconnection automatically.
- Trade-offs: Validate recommendations against monitoring, workload profiles, and vendor documentation before making changes.
Example
SET GLOBAL wait_timeout = 600; -- 10 minutes for idle connections
Always validate on a non-production instance first. Use SET PERSIST (MySQL 8.0+) for changes that should survive restarts.