Regularly upgrading PostgreSQL and the Citus extension keeps you on top of all the latest features and bug fixes, and on Citus Cloud an upgrade is as easy as a few clicks of a button. Just visit the Settings tab in the cloud console, and scroll down to the upgrade section:
We strongly recommend forking a formation and trying the upgrade on the fork before upgrading the production formation. It takes more time, but provides a dry run for the real upgrade.
You may want to set a maintenance window prior to starting an upgrade. Part of the upgrade process requires a few minutes of downtime, and setting a window will ensure that the downtime happens during a specific time of day. This option is available in the Settings tab of the cloud console.
When you do start the upgrade, Citus Cloud creates new servers for the coordinator and worker nodes with the requested software versions, and replays the write-ahead log from the original nodes to transfer data. This can take a fair amount of time depending on the amount of data in existing nodes. During the transfer, the formation overview tab will contain a notice:
When the new nodes have caught up (and during a maintenance window if one has been set), Citus Cloud switches over to the new nodes. During the period of redirection there may be a few minutes of downtime. After everything is done, the upgrade section in Settings will show:
If high-availability replication is enabled, Citus Cloud will automatically create new standby servers. However follower replicas will not receive the updates and must be manually destroyed and recreated.