# Galera

Galera is a synchronous multi-master cluster for MySQL/InnoDB databases. For more information about the product and its features, please visit the official webpage.

Note: Currently replication is supported only for InnoDB tables.

## Installation

The two components Galera cluster comprised of are Galera plugin itself and a patched version of MySQL server which connect using wsrep API.

Install the mysql-wsrepAUR[broken link: archived in aur-mirror] and galeraAUR packages from the AUR.

Start/Enable the `mysqld.service` daemon.

## Installation MariaDB

MariaDB V>10.1 is ready to use galera / wsrep out of the box. [1]

Install these packages:

- mariadb — Standard MariaDB Package
- galeraAUR — ATM this package does not install the galera library to the right place so you should Galera#Compile Galera yourself.

## Configuration

Once you have installed the galeraAUR and mysql-wsrepAUR[broken link: archived in aur-mirror] packages, you need to configure the cluster.

On each node edit `/etc/mysql/my.cnf` and update the wsrep_cluster_address variable so it contains the list of all nodes in the cluster:

    wsrep_cluster_address="gcomm://192.168.1.4,192.168.1.5,192.168.1.6"

Change the variables wsrep_node_address and wsrep_node_name to the IP address/hostname and name(this doesn't need to be unique) for each node, e.g.:

    wsrep_node_address='192.168.1.4'
    wsrep_node_name='node1'

The wsrep_cluster_name variable should contain the same name for all cluster nodes:

    wsrep_cluster_name='my_galera_cluster'

Also, set wsrep_sst_method to the desired state snapshot transfer method, the preferred one is rsync.

    wsrep_sst_method=rsync

When you have finished with `/etc/mysql/my.cnf`, start the mysqld service on the first node:

    # systemctl start mysqld-bootstrap.service

This will bootstrap the cluster. Use MySQL's command line tool to log in as root into your MySQL server:

    $ mysql -p -u root

Check the status of the cluster:

    mysql> SHOW STATUS LIKE 'wsrep_%';

This will show you wsrep-related status variables:

    ...
    | wsrep_local_state          | 4                                    |
    | wsrep_local_state_comment  | Synced                               |
    | wsrep_cert_index_size      | 0                                    |
    | wsrep_causal_reads         | 0                                    |
    | wsrep_incoming_addresses   | 192.168.1.4:3306                     |
    | wsrep_cluster_conf_id      | 1                                    |
    | wsrep_cluster_size         | 1                                    |
    | wsrep_cluster_state_uuid   | 6cd96745-2ea8-11e3-bbc8-d666651b51ef |
    | wsrep_cluster_status       | Primary                              |
    | wsrep_connected            | ON                                   |
    | wsrep_local_index          | 0                                    |
    | wsrep_provider_name        | Galera                               |
    ...

If you use xtrabackup or mysqldump SST method, you will need to create a MySQL user for sst transfers.

Once you configured the first node, you should be able to start all other nodes with:

    # systemctl start mysqld.service

## Compile Galera

- Download galera from github Galera Releases
- Extract content and run scons in root directory

    $ tar xvfz release_*.tar.gz && cd galera_release_* && scons

- Copy lib to `/usr/lib/galera/libgalera_smm.so`

    $ sudo mkdir /usr/lib/galera && sudo cp libgalera_smm.so /usr/lib/galera/

## See also

Galera Wiki Percona XtraDB Cluster’s documentation

Category:

- Database management systems

Hidden category:

- Pages with broken package links