Decomposing application to effectively use Docker often requires multiple running containers of different Docker images. If your application has multiple containers that are linked to each other, manually coordinating the management of application's Docker containers (starting, stopping, and so on) can be time consuming and prone to errors, especially if you forget any of the necessary parameters for specific containers (that is, you may have a volume container that is linked to your application container, with your application container requiring different port mappings). Fortunately, there is an open source project, Docker Compose, sponsored by Docker, Inc. that alleviates a lot of these problems.
Docker Compose is automatically included if you installed Docker Toolbox. Docker Compose can also be installed by following the directions at http://docs.docker.com/compose/. To illustrate the use of Docker Compose in an application, we'll create...