Docker Swarm is the choice of several projects, for example:
Rackspace Carina is built atop Docker Swarm: Rackspace offers hosted container environment, which is internally based on Docker Swarm
Zenly is using Swarm across Google Cloud Platform and bare metal servers
ADP uses Docker and Swarm to give velocity to their legacy deployments
Swarms can be deployed with Amazon AWS and Microsoft Azure templates directly on their public clouds
There are two opposite approaches when creating and utilizing infrastructures: pet versus cattle.
In the pet model, the administrator deploys servers or virtual machines or, in our case, containers and takes care of them. She or he logs in, installs software, configures it, and ensures that everything is working fine. As a result, this is her or his pet.
By contrast, the administrator doesn't really care about the destiny of his infrastructural components, when thinking of them as cattles. She or he doesn't log in to every single unit or handle it manually, rather, uses a bulk approach, deployment, configuration, and management are done with automation tools. If a server or container dies, it's automatically resurrected, or another is generated to substitute for the defunct. As a result, the operator is handling cattle.
In this book, we'll use the pet model in the very first chapter to introduce some basic concepts to the reader. But we'll follow the cattle pattern later, when it will be the time to do serious things.