Last night some of our servers restarted after scheduled updates, and we awoke to warning emails that some of our GIS web services were down. The affected WMS/WFS services were from GeoServer, so we knew immediately what to look for as this has happened before… the “Store” representing the connection to the GIS data repository – in this case a PostGIS database - had switched itself off, or become disabled:

Ticking the box and saving the Store fixed the problem.

Our hypothesis is that if the GeoServer service is re-started when the database server is not yet available, GeoServer automatically disables the affected Stores. [I later found this discussion in which one of the GroServer developers confirms that "the startup code checks if the stores are available, and if not, it
disables them".

We will try to prevent this happening again by ensuring that the GIS server is restarted well after the database servers, but we’d welcome any other ideas.