title: Issue with dsbulk unload
body: <p>I am getting the below messages while unloading using dsbulk. I am not able to figure out what this means</p>
  
  <p>[s0|347101951|0] Error sending cancel request. This is not critical (the request will eventually time out server-side). (HeartbeatException: null)</p>
  
  <p>Not sending heartbeat because a previous one is still in progress. Check that advanced.heartbeat.interval is not lower than advanced.heartbeat.timeout.</p>
  
  <p>Thanks</p>