“- Is my server up?
– I don’t know.”
Right. Exactly what I need from a monitoring system.
One of the biggest and long-standing shortcomings of Zabbix was its handling of “unsupported” items (the other one is the lack of security, but that’s for another day). “Unsupported” means that if for whatever reason (network failure, unexpected results, just zabbix-agent going haywire, etc) Zabbix server couldn’t retrieve a valid value from the agent. And then the triggers using that that item would switch into “Unknown” state. And there no alert, no state color change in the web interface, NOTHING. Honestly, I don’t know what could a man designing that possibly think.
Fortunately, after only 10 years or so of development and LOTS, LOTS of user input a decision was made that a monitoring system should actually be reliable to be useful. Zabbix 2.2 introduced new internal events that allow to send alerts on unknown triggers and unsupported items. Of course, it couldn’t just have been done properly from the first time, there’s a caveat: the unknown triggers will disappear from the dashboard. It doesn’t matter much if you’re the sole Zabbix person – you’ll still get emails and will at least know about the problem. But in case of a big deployment with multiple roles, where not everyone is Zabbix superadmin, it’s a drawback.
1) If you’re on Zabbix 2.2, but don’t monitor unsupported items and unknown triggers yet, configure it now.
2) If you are on Zabbix 2.0 or earlier, upgrade now and configure the alerts.
3) If for some reason you’re stuck on earlier version and can’t upgrade, take a look here. It’s a script that gathers the missing info and uses Zabbix to alert.