replica_parallel_workers
INFO
Rule IDs: rp_001
Overview
- Purpose
- Documented in the MySQL 8.4 manual as a server system variable (scope: Global). 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
- 4 (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/replication-options-replica.html#sysvar_replica_parallel_workers
- Other vendors
What is checked
Rules that reference this variable, with their severity and what each rule detects:
- INFO
rp_001: Set replica_parallel_workers > 0 (e.g., 4-16) for multi-threaded applier (MTA). Significantly improves replica catch-up speed.
Tuning guidance
- Recommended actions:
- Set replica_parallel_workers > 0 (e.g., 4-16) for multi-threaded applier (MTA). Significantly improves replica catch-up speed.
- Trade-offs: Multi-threaded replication improves apply speed but requires careful configuration (LOGICAL_CLOCK, preserve_commit_order) to maintain consistency. Misconfiguration can cause data drift between source and replica.
Example
SET GLOBAL replica_parallel_workers = 4;
-- MySQL 8.0.27+ defaults to LOGICAL_CLOCK
Always validate on a non-production instance first. Use SET PERSIST (MySQL 8.0+) for changes that should survive restarts.