When to choose .NET for Docker containers

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This content is an excerpt from the eBook, .NET Microservices Architecture for Containerized .NET Applications, available on .NET Docs or as a free downloadable PDF that can be read offline.

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The modularity and lightweight nature of .NET 8 makes it perfect for containers. When you deploy and start a container, its image is far smaller with .NET 8 than with .NET Framework. In contrast, to use .NET Framework for a container, you must base your image on the Windows Server Core image, which is a lot heavier than the Windows Nano Server or Linux images that you use for .NET 8.

Additionally, .NET 8 is cross-platform, so you can deploy server apps with Linux or Windows container images. However, if you are using the traditional .NET Framework, you can only deploy images based on Windows Server Core.

The following is a more detailed explanation of why to choose .NET 8.

Developing and deploying cross platform

Clearly, if your goal is to have an application (web app or service) that can run on multiple platforms supported by Docker (Linux and Windows), the right choice is .NET 8, because .NET Framework only supports Windows.

.NET 8 also supports macOS as a development platform. However, when you deploy containers to a Docker host, that host must (currently) be based on Linux or Windows. For example, in a development environment, you could use a Linux VM running on a Mac.

Visual Studio provides an integrated development environment (IDE) for Windows and supports Docker development.

Visual Studio for Mac is an IDE, evolution of Xamarin Studio, that runs on macOS and supports Docker-based application development. This tool should be the preferred choice for developers working in Mac machines who also want to use a powerful IDE.

You can also use Visual Studio Code on macOS, Linux, and Windows. Visual Studio Code fully supports .NET 8, including IntelliSense and debugging. Because VS Code is a lightweight editor, you can use it to develop containerized apps on the machine in conjunction with the Docker CLI and the .NET CLI. You can also target .NET 8 with most third-party editors like Sublime, Emacs, vi, and the open-source OmniSharp project, which also provides IntelliSense support.

In addition to the IDEs and editors, you can use the .NET CLI for all supported platforms.

Using containers for new ("green-field") projects

Containers are commonly used in conjunction with a microservices architecture, although they can also be used to containerize web apps or services that follow any architectural pattern. You can use .NET Framework on Windows Containers, but the modularity and lightweight nature of .NET 8 makes it perfect for containers and microservices architectures. When you create and deploy a container, its image is far smaller with .NET 8 than with .NET Framework.

Create and deploy microservices on containers

You could use the traditional .NET Framework for building microservices-based applications (without containers) by using plain processes. That way, because the .NET Framework is already installed and shared across processes, processes are light and fast to start. However, if you are using containers, the image for the traditional .NET Framework is also based on Windows Server Core and that makes it too heavy for a microservices-on-containers approach. However, teams have been looking for opportunities to improve the experience for .NET Framework users as well. Recently, size of the Windows Server Core container images have been reduced to >40% smaller.

On the other hand, .NET 8 is the best candidate if you're embracing a microservices-oriented system that is based on containers because .NET 8 is lightweight. In addition, its related container images, for either Linux or Windows Nano Server, are lean and small, making containers light and fast to start.

A microservice is meant to be as small as possible: to be light when spinning up, to have a small footprint, to have a small Bounded Context (check DDD, Domain-Driven Design), to represent a small area of concerns, and to be able to start and stop fast. For those requirements, you will want to use small and fast-to-instantiate container images like the .NET 8 container image.

A microservices architecture also allows you to mix technologies across a service boundary. This approach enables a gradual migration to .NET 8 for new microservices that work in conjunction with other microservices or with services developed with Node.js, Python, Java, GoLang, or other technologies.

Deploying high density in scalable systems

When your container-based system needs the best possible density, granularity, and performance, .NET and ASP.NET Core are your best options. ASP.NET Core is up to 10 times faster than ASP.NET in the traditional .NET Framework, and it leads to other popular industry technologies for microservices, such as Java servlets, Go, and Node.js.

This approach is especially relevant for microservices architectures, where you could have hundreds of microservices (containers) running. With ASP.NET Core images (based on the .NET runtime) on Linux or Windows Nano, you can run your system with a much lower number of servers or VMs, ultimately saving costs in infrastructure and hosting.

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