I apologise for my misunderstanding. What I remember is, during DockerCon in June 2016, I went into the code to see how it worked, and I found a top-level file

I apologise for my misunderstanding. What I remember is, during DockerCon in June 2016, I went into the code to see how it worked, and I found a top-level file setting up data structures and handlers that seemed to be 90% the same as the equivalent file in etcd. And the underlying implementation is reused via vendoring. Maybe this rings a bell with you and you can tell me what I saw, because I can't find it now. Maybe I dreamed the whole thing. I did, and still do, think integrating etcd into Swarm Mode was a masterstroke; we had spent the previous two years working to avoid "first you must install etcd" in a different way that nobody got. Afterwards we created kubeadm to ape the 'init' and 'join' functionality.