MySQL Group Replication (MGR) provides a fault-tolerant, multi-primary or single-primary cluster using Paxos-based distributed consensus. It is the foundation for MySQL InnoDB Cluster.
Single-Primary vs Multi-Primary
- Single-primary: One writable primary, automatic failover — simpler, recommended for most workloads
- Multi-primary: All nodes accept writes — complex conflict detection, avoid unless needed
Prerequisites
- All nodes: MySQL 8.0+, GTID enabled, row-based replication
- All nodes must have unique
server_idandserver_uuid - Firewall: open port 33061 (group communication port)
my.cnf Configuration (Each Node)
ini
[mysqld]
server_id = 1 # unique per node
gtid_mode = ON
enforce_gtid_consistency = ON
binlog_format = ROW
log_replica_updates = ON
plugin_load_add = group_replication.so
group_replication_group_name = 'aaaaaaaa-bbbb-cccc-dddd-eeeeeeeeeeee'
group_replication_start_on_boot = OFF
group_replication_local_address = '10.0.1.10:33061'
group_replication_group_seeds = '10.0.1.10:33061,10.0.1.11:33061,10.0.1.12:33061'
group_replication_bootstrap_group = OFFBootstrap the First Node
sql
-- On node1 only, once
SET GLOBAL group_replication_bootstrap_group = ON;
START GROUP_REPLICATION;
SET GLOBAL group_replication_bootstrap_group = OFF;Join Additional Nodes
sql
-- On node2 and node3
CHANGE MASTER TO MASTER_USER='replication_user', MASTER_PASSWORD='password'
FOR CHANNEL 'group_replication_recovery';
START GROUP_REPLICATION;Check Group Status
sql
SELECT MEMBER_ID, MEMBER_HOST, MEMBER_PORT, MEMBER_STATE, MEMBER_ROLE
FROM performance_schema.replication_group_members;Key Takeaways
- Use single-primary mode unless you have a specific multi-primary use case
- GTID and row-based replication are mandatory prerequisites
- Bootstrap (
group_replication_bootstrap_group = ON) only on the first node, only once - Monitor
replication_group_membersfor node state and role
JusDB Can Help
MySQL Group Replication has complex failure modes. JusDB can design and support your MGR or InnoDB Cluster deployment.