mariadb-core-replication-model

Architectural reference for MariaDB replication. Covers the three replication shapes, the MariaDB-specific GTID format, binary log formats, the parallel-applier model, and multi-source replication. Topology setup details and recovery procedures live in references/.

Quick Reference

• Async is the default. Primary writes the binary log, replica I/O thread fetches events into the relay log, replica SQL thread (or parallel workers) applies them. The primary does NOT wait for replicas. RPO depends on replication lag.
• Semi-sync is built into the server from MariaDB 10.3+. NEVER install a separate plug-in on 10.3 or later. Enable via rpl_semi_sync_master_enabled=ON on the primary plus rpl_semi_sync_slave_enabled=ON on the replica. Default rpl_semi_sync_master_timeout is 10000 ms ; on timeout the primary reverts to async until a replica re-ack.
• Parallel-applier default mode is optimistic since MariaDB 10.5.1+. Older 10.5.0 and earlier used conservative. Set worker pool with slave_parallel_threads. Both primary and replica MUST be MariaDB 10.0.5 or later.
• MariaDB GTID format is domain-server-sequence (for example 0-1-1234). MySQL GTID format is uuid:seqno. The schemes are NOT interconvertible. Per the KB : "MariaDB can be a replica for a MySQL primary, but MySQL cannot be a replica for a MariaDB primary." Migration between the two with GTID is a one-shot dump-and-load, NEVER continuous GTID-tracked replication.
• Binary log default format is MIXED since MariaDB 10.2.4 (was STATEMENT until 10.2.3). MIXED auto-switches to row-encoding when a statement is unsafe (non-deterministic functions, LIMIT without ORDER BY, certain stored routines). Use ROW explicitly for Galera and for any cluster that cannot tolerate replication drift.
• binlog_row_image default is FULL. Other values : MINIMAL, NOBLOB ; MariaDB 11.4+ adds FULL_NODUP. NEVER set MINIMAL in environments that need point-in-time recovery with full row reconstruction.
• Multi-source replication uses NAMED CONNECTIONS, not FOR CHANNEL. Syntax is CHANGE MASTER 'connection_name' TO .... The FOR CHANNEL syntax is MySQL-only. Connection names are case-insensitive. Use SHOW ALL SLAVES STATUS to see all channels at once.
• Seconds_Behind_Master is unreliable. It measures the timestamp on the SQL thread relative to the event being applied, NOT actual wall-clock lag. Use pt-heartbeat (or the equivalent token-based heartbeat) for accurate lag measurement.

Decision Tree : Which Replication Model