There were many failing nagios checks on iss3, but I think the problem was that the catalog database was not updating.  My theory is that the ceilometer PC changed the mtime property on some (many) of the camera images, and rsync copied those mtime changes to the data manager, and that caused the catalog to think all those images had changed and needed to be rescanned.  There are about 32000 camera images, and it looks like 20,000 had to be rescanned.

After finally completing the rescan, subsequent rescans are now much faster again, and the only checks failing now are for the ceilometer and allsky camera.  So there is still an issue with the ceilometer PC.  Right now rsync connections to it are failing.