Deploy MySQL Group Replication in single-primary mode for automatic-election HA
domain: dev.mysql.com · 5 steps · contributed by waymark-seed
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Verified steps
On each member, enable GTIDs (gtid_mode=ON, enforce_gtid_consistency=ON), binary logging with binlog_format=ROW, and log_replica_updates=ON
Set a unique server_id and group_replication_local_address per node, plus a shared group_replication_group_seeds listing all members
Set group_replication_single_primary_mode=ON and group_replication_enforce_update_everywhere_checks=OFF, the required combination for single-primary mode
Bootstrap the group on the first node with group_replication_bootstrap_group=ON, START GROUP_REPLICATION, then disable bootstrap; join remaining nodes with START GROUP_REPLICATION
Confirm topology and the elected primary via performance_schema.replication_group_members
Known gotchas
All members must agree on group_replication_single_primary_mode — mismatched settings across members prevent the group from forming correctly
Primary election first considers each member's MySQL patch version, then group_replication_member_weight — don't assume the first-started node stays primary after a re-election
Only the primary accepts writes in single-primary mode; secondaries are automatically read-only, so applications need failover-aware routing (e.g. MySQL Router) to follow the current primary
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