title: Dynamically remove duplicate log messages
body: <p>Recently we had a message fill up /var/log/libvirt/qemu/.log in a matter of minutes with a line that repeated that crashed our system due to  the root partition being filled (20+ Gigs in minutes).</p>
  
  <p>"block I/O error in device 'drive-virtio-disk0': Operation not permitted (1)"</p>
  
  <p>Is there a way to ensure that duplicate lines are not pushed into logs, or a way to limit that directory from filling up?  Logstash maxsize will not work for us since we run it on a daily cronjob.</p>