Enable parallel replication applier threads (#116)

Author: Wiktor Maj

CHANGELOG.md

@@ -21,6 +21,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 * Completed [ARCHITECTURE.md](./docs/ARCHITECTURE.md) (#93)
 * Migrated CI from self-hosted to GitHub-hosted runners with Docker-in-Docker test infrastructure. (#94)
 * Test workflow always builds service images locally for reproducibility. (#97)
+* Enabled parallel replication applier threads on secondary MySQL nodes. (#75)
 * Clean up temporary `.pyc` files on remote nodes after execution. (#51)
 * Set `innodb_flush_method=O_DIRECT` to eliminate double caching in containers. (#74)
 * Reduced InnoDB change buffer size for read-heavy BI workload. (#72)

services/mysql-server/mysql_config.cnf.tpl

@@ -14,6 +14,9 @@ ssl-key = "/etc/mysql/ssl/mysql_server_key.pem"
 require_secure_transport = "ON"
 max_connections = "50"
 max_connect_errors = "50"
+replica_parallel_workers = "4"
+replica_parallel_type = "LOGICAL_CLOCK"
+replica_preserve_commit_order = "ON"
 innodb_flush_method = "O_DIRECT"
 innodb_change_buffer_max_size = "10"
 innodb_buffer_pool_size = "1G"