Designing for MaxScale's Galera Monitor

MaxScale's Galera Monitor (galeramon) monitors Galera Cluster deployments.

This page contains topics that need to be considered when designing applications that use the Galera Monitor.

• How do I allow SST donors to execute queries?

Additional information is available here.

Understanding MaxScale's Galera Monitor

MaxScale's Galera Monitor (galeramon) monitors Galera Cluster deployments.

What Does the Galera Monitor Support?

The Galera Monitor (galeramon) supports:

• Monitoring MariaDB Enterprise Cluster deployments

• Monitoring MariaDB Galera Cluster deployments

• Query-based load balancing with the Read/Write Split Router (readwritesplit)

• Connection-based load balancing with the Read Connection Router (readconnroute)

Deploying Galera Monitor

• Deploy MaxScale with Galera Monitor and Read/Write Split Router

• Deploy MaxScale with Galera Monitor and Read Connection Router

Using SST Donors for Queries with MaxScale's Galera Monitor

MaxScale's Galera Monitor (galeramon) monitors Galera Cluster.

By default, when a node is chosen as a donor for a State Snapshot Transfer (SST), Galera Monitor does not route any queries to it. However, some SST methods are non-blocking on the donor, so this default behavior is not always desired.

Non-Blocking SST Methods

A cluster's SST method is defined by the wsrep_sst_method system variable. When this system variable is set to mariabackup, the cluster uses MariaDB Backup to perform the SST. MariaDB Backup is a non-blocking backup method, so Galera Cluster allows the node to execute queries while acting as the SST donor.

Configuring Availability of SST Donors

1. Configure the availability of SST donors by configuring the available_when_donor parameter for the Galera Monitor in maxscale.cnf.

For example:

[galera-cluster]
type                     = monitor
module                   = galeramon
...
available_when_donor     = true

2. Restart the MaxScale instance.

$ sudo systemctl restart maxscale