====== MariaDB galera ======

===== Links =====

  * [[http://www.fromdual.com/making-haproxy-high-available-for-mysql-galera-cluster|Bespielsetup mit keepalived]] (failover IP) auf zwei haproxy-Instanzen (die ein frontend + backend auf die galera-nodes aufmacht)
  * https://computingforgeeks.com/how-to-setup-mariadb-galera-cluster-on-ubuntu-18-04-with-haproxy/
  * [[https://mariadb.com/kb/en/mariadb-galera-cluster-known-limitations/|limitations]]


===== Installation =====

[[https://github.com/selfhostx/ansible/blob/main/playbooks/database/galera.yml|Bespielplaybook]] der Rolle
[[https://github.com/mrlesmithjr/ansible-mariadb-galera-cluster|mrlesmithjr.mariadb_galera_cluster]].


===== Cluster OK =====

<code sql>SHOW STATUS LIKE 'wsrep%';</code>

[[https://galeracluster.com/library/documentation/monitoring-cluster.html|Erklärung der Metriken]]

<code sql>
show status like 'wsrep_cluster_size';
+--------------------+-------+
| Variable_name      | Value |
+--------------------+-------+
| wsrep_cluster_size | 3     |
+--------------------+-------+

show status like 'wsrep_cluster_status';
+----------------------+---------+
| Variable_name        | Value   |
+----------------------+---------+
| wsrep_cluster_status | Primary |
+----------------------+---------+

show status like 'wsrep_local_state_comment';
+---------------------------+--------+
| Variable_name             | Value  |
+---------------------------+--------+
| wsrep_local_state_comment | Synced |
+---------------------------+--------+

show status like 'wsrep_last_committed';
+----------------------+---------+
| Variable_name        | Value   |
+----------------------+---------+
| wsrep_last_committed | 7560036 |
+----------------------+---------+
</code>


===== Recovery =====

https://www.symmcom.com/docs/how-tos/databases/how-to-recover-mariadb-galera-cluster-after-partial-or-full-crash

interesting files: cat /var/lib/mysql/grastate.dat

/etc/mysql/conf.d/galera.cnf -> wsrep_cluster_address