With everything we've done until now, not to mention the tasks we'll do throughout the rest of the book, we are simultaneously decreasing and increasing the complexity of our system. Scaling a service is easier and less complex with Docker Swarm than it would be with containers alone. The fact is that Docker already simplified a lot the process we had before. Add to that the new networking with service discovery baked in, and the result is almost too simple to be true. On the other hand, there is complexity hidden below the surface. One of the ways such complexity manifests itself can be easily observed if we try to combine dynamic tools we have used so far, with those created in (and for) a different era.
Take Nagios (https://www.nagios.org/) as an example. I won't say that we could not use it to monitor our system (we certainly can). What I will state is that it would clash with the new system architecture we've designed so far. Our system...
