MariaDB Galera

MariaDB Galera is a high-availability deployment model built on Galera replication. dbdeployer supports it with the galera topology.

5-Minute Tutorial

This example uses MariaDB 10.11. Use a MariaDB tarball that includes Galera support.

1. Install Runtime Tools

MariaDB Galera deployments run only on Linux. The host must have socat, rsync, and the usual MariaDB shared-library dependencies available.

sudo apt-get update
sudo apt-get install -y libaio1 libnuma1 libncurses5 socat rsync

Some older MariaDB tarballs may also require legacy OpenSSL libraries on newer Linux distributions.

2. Unpack a MariaDB Tarball

dbdeployer unpack mariadb-10.11.21-linux-systemd-x86_64.tar.gz
dbdeployer versions
# 10.11.21

If the tarball does not contain Galera libraries, --topology=galera is rejected.

3. Deploy the Cluster

dbdeployer deploy replication 10.11.21 --topology=galera

The default deployment creates three writable Galera nodes:

~/sandboxes/galera_msb_10_11_21/
├── node1/
├── node2/
├── node3/
├── check_nodes
├── start_all
├── stop_all
└── use_all

4. Check Cluster Health

~/sandboxes/galera_msb_10_11_21/check_nodes

Each node should report a cluster size of 3 and a synced local state.

5. Verify Writes Replicate

Write on one node and read from another:

~/sandboxes/galera_msb_10_11_21/n1 -e "CREATE DATABASE galera_demo"
~/sandboxes/galera_msb_10_11_21/n1 -e "CREATE TABLE galera_demo.t1(id INT PRIMARY KEY, val VARCHAR(50))"
~/sandboxes/galera_msb_10_11_21/n1 -e "INSERT INTO galera_demo.t1 VALUES (1, 'galera works')"
~/sandboxes/galera_msb_10_11_21/n3 -e "SELECT * FROM galera_demo.t1"

ProxySQL Tutorial

Add --with-proxysql when deploying the topology. proxysql must be in PATH.

dbdeployer deploy replication 10.11.21 --topology=galera --with-proxysql

Check that ProxySQL has all three MariaDB Galera nodes registered:

~/sandboxes/galera_msb_10_11_21/proxysql/use -e "SELECT hostgroup_id, hostname, port FROM mysql_servers"

Run a query through ProxySQL:

~/sandboxes/galera_msb_10_11_21/proxysql/use_proxy -e "SELECT @@port"

Cleanup

dbdeployer delete galera_msb_10_11_21 --skip-confirm

Reference

MariaDB Galera requires a MariaDB tarball that includes the Galera library and wsrep support.

dbdeployer deploy replication 10.11.21 --topology=galera

The generated sandbox directory is ~/sandboxes/galera_msb_<version>/, where dots in the version are converted to underscores.

Generated scripts include:

start_all and stop_all to control the whole cluster
check_nodes to inspect wsrep cluster state
use_all to run a query on every node
n1, n2, and n3 shortcuts for individual nodes

Galera topology requires at least three nodes. Options that make nodes read-only are rejected because Galera topologies are designed as writable clusters.

How It Works

Galera uses synchronous write-set replication:

A transaction is executed on any node.
The write set is broadcast to the other nodes.
All nodes certify it for conflicts.
If it passes, the transaction commits cluster-wide.

Every node can accept writes, so dbdeployer generates a multi-node sandbox with identical access scripts on each node.