title: Prometheus Query Overall average under a time interval
body: <p>How can I find the overall average of metrics over time interval ?</p>
  
  <p><em>avg(metric) = overall average value</em>
  but </p>
  
  <p><strong>avg_over_time(metrics[interval]) = averages value per label</strong></p>
  
  <p><em>avg( avg_over_time(metric[scrape interval]) )</em>  <strong>won't be same as</strong>(when the data is not continuous and denominator value is different) <em>avg(metric)</em> !!!!</p>
  
  <p>Given a scenario, what will be the possible way to find the overall average over a time period.</p>
  
  <p>Eg: Find the average response time now and Find the average response time(over all) of all the request triggered in last one hour.</p>
  
  <p>The <strong>number</strong> will be helpful to notify a performance issue with latest upgrades.</p>