Docker Swarm v1 includes an out-of-the-box discovery service, called Token. Token is integrated into the Docker Hub; hence, it requires all the Swarm nodes to be connected to the Internet and able to reach the Docker Hub. This is the main limitation of Token but, you will soon see, Token will allow us to make some practice in handling clusters.
In a nutshell, Token requires you to generate a UUID called, in fact, token. With this UUID, you can create a manager, act like a master, and join slaves to the cluster.
If we want to keep it practical, it's time to take a look at an example. We'll use token to re-architect the example of Chapter 1, Welcome to Docker Swarm. As a novelty, the cluster will be not flat anymore, but it will consist of 1 master and 3 slaves and each node will have security enabled by default.
The master node will be the node exposing Swarm port 3376
. We'll connect specifically to it in order to be able to drive the...