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Portal:Cloud VPS/Admin/Galera
The databases for OpenStack services are stored on a Galera cluster hosted on the cloudcontrol nodes. This cluster does not use custom WMF packages; it runs the standard packages from upstream Debian. The cluster is active/active/active which means that write actions can be taken on any of the cloudcontrol nodes.
OpenStack services tend to use connection pooling, opening many long-lived connections to each database. For this reason, our Galera config has extremely long connection timeouts and very high connection limits.
For troubleshooting immediate Galera problems, consult Portal:Cloud_VPS/Admin/Troubleshooting. Directions for standing up a new cluster are included in puppet/modules/galera/manifests/init.pp.