Question
Icinga 2 as core, Icinga Web 2, etc. need additional monitoring - whether it runs, and performance metrics.
Solution
Check the documentation for in-depth description of possible implementations, including plugins and check commands.
https://icinga.com/docs/icinga2/latest/doc/08-advanced-topics/#monitoring-icinga-2
More?
Please share your own examples, how you monitor your monitoring 