Docker is a tool to help in the deployment of applications across host systems. Virtualization, union file systems, image registries, orchestration services - while Docker is a useful tool for staging and deployment, there is a learning curve to get to grips with the whole ecosystem.

Docker is extremely useful for deploying packages, but also for creating environments for running functional tests. Here I show how to easily setup a cluster of PostgreSQL servers in slave/master replication using Docker and drive them using the Docker Python API.