I decided to look into Docker during a migration from MySQL 5.5 to 5.6 on one of the production servers. The server hosts multiple applications and services and is running in a hot spare configuration (another server mirrors this server, acts as the MySQL slave, etc.). Thus I wanted a migration strategy where I can have the 5.6 installation ready and running on the server, so that I can test it with production data and when ready just turn the switch to replace the old 5.5. Docker turned out to be the cleanest solution.
Since the MySQL server is such a critical part of the infrastructure I decided to develop the container utilizing test driven development. This allowed me to quickly add new features, like performance optimization and replication over a ssh tunnel (to support servers in different public clouds). Having this functionality in a standalone, tested and isolated unit is amazing. Before, all this complexity would be managed by Chef provisioning, which is much harder to test and experiment with on the production server. Having this functionality contained in a Docker container allows me to just use Chef for orchestration and deployment of the containers themselves, witch requires much simpler logic, compared to provisioning a full MySQL server install, configuration, replication and upgrading.
This project is released under the MIT license.