title: How to ensure that the data pulled by Prometheus is up-to-date and does not include old data before the pull interval
body: <blockquote>
    <p>The Prometheus interval pulls data from the pushgateway. The pushgateway uses the “-persistence.file string” data persistence parameter configuration. The client sends data to the pushgateway in real time.</p>
    
    <p>If Prometheus pulls data within the time interval. Pushgateway did not
    receive data from the client. What happens when Prometheus pulls data
    from the pushgateway interval?</p>
    
    <ol>
    <li>Will Prometheus pull old data outside the time interval, and then take the pull time as the time of the old data?</li>
    <li>Prometheus will judge according to the pull time interval, pushgateway no new data during this period, and then pull the data is empty?</li>
    <li>Still have other results</li>
    </ol>
  </blockquote>