[amm]

We use docker extensively to ship a large and complex legacy platform that was designed to run as a hosted service, but was transformed into an on-premise product.

The system is composed of several components originally designed to run on separate VMs for security reasons. Luckily, we were able to translate VM <-> docker container, so now each component has its own Dockerfile + shell script for booting up and providing runtime configuration.

Docker helps us solve several problems:

* A canonical build. It provides a way to configure the build system, fetch all dependencies and execute a reproducible build on different machines/environments. It's also used as documentation when engineers have no clue, where settings/parameters come from.

* A super fast build pipeline and release repository. We use maven -> nexus, docker -> docker-registry, vagrant -> local export for a completely automated way to bootstrap an ovf-file that can be deployed at customer site. Releases for the old platform were not automated and took the previous teams weeks (!) on a single platform.

* A way to restrict resources. Given some security constraints from the product, lxc + docker helps us restrict memory and networking.

* Shipping updates. We deliver automated updates through a hosted docker registry for customers who open up the appliance to the internet. Previous teams were not able deliver updates in time for a single hosted platform. We can now ship new releases and have them deployed at several customers data-centers in a matter of hours.

We have been using docker in production for almost a year now and despite headaches in the beginning it's been absolutely worth it.