This chapter was all about Docker Swarm mode, the native clustering option built right into Docker. You learned how to create a swarm, how to add and remove swarm nodes, and how to deploy services on the swarm connected with an overlay network. I showed that you have to create services for high availability and also discussed how to use configs and secrets to store sensitive application data securely in the swarm.

You can deploy your application as a stack on the swarm, using a Compose file, which makes it very easy to group and manage your application components. I demonstrated stack deployment on a single node swarm and on a multi-node swarm—and the process is the same for swarms with hundreds of nodes.

High availability in Docker Swarm means you can perform application updates and rollbacks without downtime. You can even take nodes out of commission when you need to update Windows or Docker and still have your application running with the same service level on the remaining nodes.

In the next chapter I'll look more closely at the administration options for dockerized solutions. I'll start by looking at how to use your existing management tools with applications running in Docker. Then, I'll move on to managing swarms in production, with Docker Enterprise.