title: How to trigger alert when items are unavailable?
body: <p>Using Zabbix, how can I trigger an alert if an item is unreachable (e.g. 'ZBX_NOTSUPPORTED' or any error that is traced when the zabbix agent could not provide the expected item format) ?</p>
  
  <p>The goal is to prevent hosts to silently fail on retrieving data on items.</p>