IT notes

Galera

To periodically check status of the cluster, create a script (/tmp/xx): #!/bin/sh mysql --defaults-file=/path/to/.my.cnf -s -e "SHOW GLOBAL STATUS WHERE Variable_name IN ('wsrep_ready', 'wsrep_cluster_size', 'wsrep_cluster_status', 'wsrep_connected');" And run it with: watch sh /tmp/xx If single node alive (ERROR 1047 WSREP has not yet prepared node for application use): SET GLOBAL wsrep_provider_options='pc.bootstrap=YES'; This node can be used now has the new master so others nodes can recover from it.

galera alter

To prevent bloking the cluster while doing ALTERS (SCHEMA UPGRADES), do this per node: SET wsrep_OSU_method='RSU'; Then Run the ALTER statement once done reset the Schema Upgrade method back to Total Order Isolation. SET wsrep_OSU_method='TOI'; http://galeracluster.com/documentation-webpages/clusterstallonalter.html http://galeracluster.com/documentation-webpages/schemaupgrades.html