I'm reworking an Icinga setup I inherited. One of the things it perpetually complains about is ido2db not running (and idomod unable to connect to it).
Before figuring out, how to configure/fix it, I'm trying to find out, if we even need it in the first place. Unfortunately, all of the documentation I am able to find online talks about how to configure the functionality, not why do (or not do) it...
In particular, here is the most recent error on the subject in the log:
[1504809535] idomod: Still unable to connect to data sink. 83915 items lost, 5000 queued items to flush. Is ido2db running and processing data?
I'm guessing, the "items" are the check-results, etc. What feature(s) are we not benefiting from because of the cited losses?
IDO is used for modern interfaces (Icinga Web) and things like graphing support to interact with Icinga. Basically, it writes all status information, checks etc. into an SQL database (that's ido2db's job).
If you only run a Icinga v1 interface with the classic (Nagios style) UI, you don't strictly need it, but if your reworking includes "Make Icinga not looking like a web page from 1998 anymore", you likely will end up using it.