Deploy MySQL HA

MySQL HA

A highly available MySQL cluster using:

• MySQL Group Replication (single-primary, consensus built into mysqld)
• HAProxy for client connections, routing writes to the current primary

Architecture

• MySQL-1 (Primary): Current Group Replication primary (may change after failover)
• MySQL-2+ (Replicas): Group members that elect a replacement on primary loss
• MySQL HA (Edge): HAProxy entry point - use this for all client connections

Minimum 3 MySQL nodes: Group Replication is majority-based, so a 2-node group cannot survive a symmetric partition. 3 members tolerate 1 node loss.

Connecting

Use the MYSQL_URL or MYSQL_PUBLIC_URL from the "MySQL HA" (HAProxy) service. Do not connect directly to individual MySQL nodes.

Scaling

• Replicas: even counts (2/4/6/8) via the cluster overview - the cluster totals 3, 5, 7 or 9 members, keeping the voter count odd (Group Replication caps membership at 9)