Need assistance - how can i detect the ABSENCE of a given string in a log file, and only report if its been over 10 minutes missing?

[ngacordex]

I am struggling to wrap my head around some of this - I can understand easily how to detect a string in a log file, i.e. report when an error shows up in our log file to our endpoint.

For some reason I am struggling to do the OPPOSITE - which is detect when a constantly reoccuring message is NOT there. I want to only alert when its been 10+ minutes obviously for any false positives.

Any help is appreciated...