We have more than only Docker Swarm out there to clusterize containers. For completeness, we will briefly review the most widely known open source alternatives, before diving completely into Swarm.
Kubernetes (http://kubernetes.io), also known as k8s, aims at the same goal of Docker Swarm; it's a manager for cluster of containers. Started originally as project Borg in Google laboratories, it was later open sourced and released as a stable version in 2015, supporting Google Cloud Platform, CoreOS, Azure, and vSphere.
Kubernetes so far runs containers in Docker, which is commanded via API by a so called Kubelet, a service that registers and manages Pods. Architecturally, Kubernetes divides its clusters, logically, not into ...