Review application documentation 

We begin the containerization process by collecting information about our PoC, starting with the installation process. In other words, we want to see how this application would be installed on a clean server. This information is often available from operational documentation related to the application or some sort of automated script. In other cases, where documentation or scripts are not available, a subject matter expert such as a software developer can usually help you through the process.

Our application documentation includes this diagram:

Our example PoC application architecture includes two key components: the application virtual machine and the database virtual machine. Within the database virtual machine, we see the application's database called SignUpDb, running in a SQL Server Express 2016 SP1 database on a Windows Server core 2016 operating system. Within the application virtual machine, we see our newsletter app, an ASP.NET 3.5 web forms application. The application server has the web-server, web-asp-net, and ServiceMonitor modules installed on top of a Windows Server 2016 guest operating system. Our application has two high-level processes, the application and the database. We will split each of these into a separate image and connect them together with a common network when we deploy them. When containerizing, it is often helpful to build from the bottom up, testing each of the images along the way. So, we will start with the database.