mariadb-operator/docs/HA.md

High availability

This operator supports the following High Availability modes:

• Single master HA via SemiSync Replication: The primary node allows both reads and writes, while secondary nodes only allow reads.
• Multi master HA via Galera: All nodes support reads and writes, but it is recommended to perform writes in a single primary for preventing deadlocks.

In order to address nodes, mariadb-operator provides you with the following Kubernetes Services:

• <mariadb-name>: To be used for read requests. It will point to all nodes.
• <mariadb-name>-primary: To be used for write requests. It will point to a single node, the primary.
• <mariadb-name>-secondary: To be used for read requests. It will point to all nodes, except the primary.

Whenever the primary changes, either by the user or by the operator, both the <mariadb-name>-primary and <mariadb-name>-secondary Services will be automatically updated by the operator to address the right nodes.

The primary may be manually changed by the user at any point by updating the spec.[replication|galera].primary.podIndex field. Alternatively, automatic primary failover can be enabled by setting spec.[replication|galera].primary.automaticFailover, which will make the operator to switch primary whenever the primary Pod goes down.

Although using the Kubernetes services for addressing the primary and secondary works, the most highly available setup we can offer relies on MaxScale, our advanced database proxy. Please take a look at the MaxScale docs.