If you have been paying attention, then you might have noticed something interesting in the last section. We had the pets application deployed and it resulted in the fact that an instance of the service web was installed on the three nodes node-3, node-4, and node-5. Yet, we were able to access the web service on node-1 with localhost and we reached each container from there. How is that possible? Well, this is due to the so-called swarm routing mesh. The routing mesh makes sure that when we publish a port of a service, that port is then published on all nodes of the swarm. Thus, network traffic that hits any node of the swarm and requests to use the specific port, will be forwarded to one of the service containers by routing the mesh. Let's look at the following figure to see how that works:
Docker Swarm routing mesh
In this situation we have three nodes, called Host A to Host C, with the IP addresses 172.10.0.15, 172.10.0.17, and 172.10.0.33. In the lower left-corner...