title: Docker Engine version upgrade on Docker Swarm managed nodes, without downtime
body: <p>I'd like to upgrade the Docker engine on my Docker Swarm managed nodes (both manager and worker nodes) from <code>18.06</code> to <code>19.03</code>, without causing any downtime.
  I see there are many tutorials online for rolling update of a Dockerized application without downtime, but nothing related to upgrading the Docker engine on all Docker Swarm managed nodes.</p>
  
  <p>Is it really not possible to upgrade the Docker daemon on Docker Swarm managed nodes without a downtime? If true, that would indeed be a pity.</p>
  
  <p>Thanks in advance to the wonderful community at SO!</p>