Change "No data" to zero in Grafana stat panel

Question

On a Grafana dashboard I have a stat panel showing the number of hosts that have operating system updates pending. The PromQL query looks like this (os_updates_pending is a custom OS-agnostic metric):

count(sum (os_updates_pending) by (hostname) != 0)

This works well if there are hosts with pending updates, but if there aren't I'm getting "No data" instead of "0" as a result. I know I could set the "No value" option to "0" to get a zero displayed instead, but the data link for clicking through the panel to a details view still won't work (because the value is still empty, not 0). How can I fix that?

Answer 1

To get "0" as a fallback value append or vector(0) to your query:

count(sum (os_updates_pending) by (hostname) != 0) or vector(0)