If you've started using Docker for a while you might be asking the same question «how to manage a group of Docker containers into a consistent topology?».
On your local workstation, projects such as fig simply help you do the job: local, fast, easy.
Flocker gets a step further by adding some major features:
The magic in Flocker network proxy design allows you to talk to any of the nodes to reach any container. The price is that exposed ports must be unique per container to avoid conflicts.
Flocker relies on two YAML files describing
Flocker YAML files are declarative. Flocker will perform the needed operations to comply with the YAML files, and nothing if it is all set-up. To move a container from a host simply modify the location of the container into deployment.yaml and rerun Flocker.
Actually, container motion is not the correct term as containers are destroyed on a node and then re-created on another one.
You may really have a look at two Vagrant-based tutorials to understand the basics of Flocker:
Many questions remain about flocker:
However, it's totally worth it having a look. I bet some of its ideas might probably be reused into other projects (such as Kubernetes).