Currently, when a trigger is in an unknown state, there is no alerting that happens.

This is a very bad thing. There are several things that can cause a trigger to return unknown instead of problem. This fails to trigger any alerts, as no events are created, which ultimately means that monitoring has failed to do it's job (i.e. to alert us when something changes). This makes monitoring and alerting with Zabbix untrustworthy.

We need the ability for Zabbix to send alerts when Items and Triggers become unknown.

• If a system fails to return data for an item over multiple periods, this needs to generate an alertable event.
• If a trigger fails to apply correctly, this needs to generate an alertable event.
• If an item stops collecting data because it returns ZBX_UNSUPPORTED, this needs to generate an alertable event.

Right now, we need to have everyone proactively looking for a lack of data because Zabbix is unable to alert us to this. This is a waste of man hours, and defeats the purpose of having a monitoring system.

See https://www.zabbix.org/wiki/Docs/specs/ZBXNEXT-341 for detailed specification.