title: Alert Manager Alert rules are not functioning properly
body: <p>I have a quick question on alert manager alerting rules, i have 500 IoT devices connected to the server and those are being monitored using prometheus, and i configured the alert rules in such a way to get an alert when ever a device goes offline. every thing is fine till now but, when multiple devices are going offline at different time, alert manager is sending alerts of all the players which are currently offline rather than showing the alert of particular player on particular time.</p>
  
  <pre><code>ALERT IoT_online
    IF IoT_online == 0
    LABELS {severity="critical"}
    ANNOTATIONS {description="This device is offline  {{ $value }}.", summary="Instance {{ $labels.instance }} IoT device is offline"}
  </code></pre>
  
  <p>I wanted to configure alerts in such a way that alert manager should only send alert of particular device alert on particular time rather than sending the alert of all offline devices every-time  when a device goes offline. any one can help me ?</p>
  
  <p>Thanks in advance</p>