Maintenance tab is incredibly laggy

[gregorydlogan]

Try setting your server to maintenance mode. Just wait, it'll happen eventually...

It's reflected in the backend immediately, but the UI is very slow to react. 30+ seconds by my count.

[Arnei]

The cause for this seems to lie with the backend. The admin ui backend caches server information for 60 seconds before getting new information, so it can take up to a minute before the admin ui is informed about any changes: https://github.com/opencast/opencast/blob/74b784d5f68b0c8bad7c47b453718b6c5b670799/modules/admin-ui/src/main/java/org/opencastproject/adminui/endpoint/ServerEndpoint.java#L269

Quoting the commit that introduced the caching:

Cache Server Statistics

This add caching to the admin interface's server statistics endpoint to
avoid putting a high load on the database by having this open multiple
times.
(opencast/opencast#2851)

So we probably don't want to remove caching. A higher refresh rate might work, but also increases the risk of overwhelming the database. Alternatively, figuring out why this in particular generates such a high load and make it not do that is probably the ideal, but also more time-consuming approach.