= Mariadb Server =

What we really want to set up is a galera cluster. We will use 3 systems for this.

 * 192.168.1.50 mariadb (virtual IP)
 * 192.168.1.51 mariadb01
 * 192.168.1.52 mariadb02
 * 192.168.1.53 mariadb03

== Software ==
{{{
apt-get install mariadb-server rsync
}}}

== Configuration ==

Set the mariadb root password.
{{{
mysql_secure_installation
}}}

Stop mariadb on all nodes.
{{{
service mariadb stop
}}}
Configure mariadb to listen on all interfaces by commenting in `/etc/mysql/mariadb.conf.d/50-server.cnf`.
{{{
#bind-address           = 127.0.0.1
}}}
Add the configuration for galera to `/etc/mysql/conf.d/galera.cnf`. Replace names so they fit the current node. For some reason this has to contain the IP-addresses of the hosts instead of the hostnames.
{{{
[galera]
wsrep_on=ON
wsrep_provider=/usr/lib/galera/libgalera_smm.so
wsrep_cluster_address=gcomm://mariadb01,mariadb02,mariadb03
wsrep_node_address=192.168.1.51
wsrep_node_name=mariadb01.kallenberg.dk
binlog_format=row
default_storage_engine=InnoDB
innodb_autoinc_lock_mode=2
wsrep_cluster_name="mariadb_galera" 
wsrep_sst_method=rsync
bind-address=0.0.0.0
}}}

On the first node the cluster is started.
{{{
galera_new_cluster
}}}

On additional nodes the service is started.
{{{
service mariadb start
}}}

== Health Checks ==
To enable HA-proxy to be able to perform health checks, we have to create a haproxy user on the galera cluster. Requests can come from both haproxy01 and haproxy02.
{{{
create user 'haproxy'@'192.168.1.45';
create user 'haproxy'@'192.168.1.46';
}}}
== Checkmk Checks ==
To enable checkmk monitoring, we have to create a checkmk user on the galera cluster.
{{{
create user 'checkmk' identified by 'checkmkpassword';
}}}
== References ==
 * https://blog.cloudandheat.com/index.php/en/2016/09/09/tutorial-simple-mariadb-galera-cluster-with-haproxy-load-balancing/
 * https://linuxresolved.com/troubleshooting-galera-cluster-wont/