title: Need for service discovery for docker engine swarm mode
body: <p>I'm confused about docker swarm. As far as I know, the old way to run a swarm was to run manager and workers in containers, before docker engine provided native support for swarm mode. Documentation for the old, containerized swarm explained how to setup service discovery using consul, etcd or zookeeper. Service discovery is necessary, as services are ran at random ports to avoid collisions,  right?</p>
  
  <p>Documentation for the docker engine swarm mode doesn't explain how to setup service discovery. Now I'm confused, if the mechanism is included in swarm mode, or is the documentation incomplete.</p>
  
  <p>Where I can find clear, up-to-date explanation of swarm mode, and how it relates to concepts like service discovery? </p>