Summary
This chapter was all about the Docker swarm mode, the native clustering option built right into Docker. You learned how to create a swarm and how to add and remove swarm nodes anddeploy 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 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 running in Azure and managed with Docker Cloud.
High availability in the 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 have your application still running with the same service level on the remaining nodes.
In the next chapter, I'll look...
