Here's what you'll need:
- Unreal Engine container images that include the Engine Tools and support building for the desired target platform(s)
- Environments configured for running the containers for each applicable host platform
- Key considerations
- Implementation guidelines
- Related media
- Related repositories
One of the most common uses of Unreal Engine containers is to provide reproducible environments within which automated builds of Unreal projects and plugins can be performed. These environments can be used with any existing CI system that supports Docker containers, allowing developers to utilise their preferred infrastructure and leverage existing CI/CD workflows. These workflows can also be extended to produce container images that can then be used to run packaged Unreal projects in the cloud, facilitating other use cases such as cloud rendering and building microservices powered by the Unreal Engine. The built container images can also be deployed and scaled with standard container orchestration technologies, allowing developers to comply with existing best practices for running containerised applications.
Methods of building and packaging Unreal projects that utilise a graphical interface will not work inside containers. If you are not already accustomed to building and packaging projects via the command-line then you should take the time to familiarise yourself with this process on a host system before attempting to perform packaging inside Docker containers.
You will need to make sure your chosen CI system supports running build commands inside Docker containers. If you are using Windows containers then you will also need to check that specific support for Windows containers is included, as some CI systems only include support for Linux containers.
If you’re building Docker images for deploying packaged projects then you will need to make sure your chosen CI system supports building container images from Dockerfiles.
Using the tools that ship with the Engine
Building and packaging
The primary method of building and packaging Unreal projects and plugins via the command-line is using commands provided by the Unreal Automation Tool (UAT):
BuildCookRuncommand is used for building and packaging projects.
BuildPlugincommand is used for building and packaging plugins.
These commands can be invoked by using the
RunUAT helper script, which is located under the
Engine/Build/BatchFiles subdirectory of the Unreal Engine installation root. The same commands that are used to package projects and plugins on a host system can be used to package projects and plugins within any Unreal Engine container that includes the Engine Tools.
Copying packaged files
Once a project or plugin has been built and packaged there are a number of available mechanisms that can be used to copy the packaged files to the desired location:
Uploading files to remote storage. File upload commands can be run directly inside Unreal Engine containers if desired. However, in most typical scenarios the CI system orchestrating the build will take responsibility for handling any permanent storage of build products.
Copying the files to bind-mounted host filesystem directories. This is typically the most common approach, since the CI system orchestrating the build can then identify the build products on the host filesystem and take the appropriate actions to copy them to permanent storage locations.
Copying the files to a new container image for deployment. If you are planning to deploy a packaged Unreal project using Docker containers then you can create the container images as part of the overarching build process. See the Building container images for deployment section below for more details on this option.
Prior to Unreal Engine version 4.21, the only testing mechanism exposed via the command-line was the Automation System, which can be accessed via the
automation console command, either by invoking the Editor directly or via the
BuildCookRun command provided by UAT. The command to run automation tests through the Editor directly looks like this:
The command to run automation tests through UAT looks like this:
Unreal Engine 4.21.0 introduced the Gauntlet Automation Framework, which allows developers to specify tests using C# scripts that are then run by the
RunUnreal command provided by UAT. However, at the time of writing there is very little available documentation for Gauntlet and the authors of this documentation have not tested the use of Gauntlet within Unreal Engine containers.
Using third-party infrastructure and abstractions
There are a number of infrastructure projects maintained by the community that abstract the process of building and packaging Unreal projects and plugins. These infrastructure projects typically automate the process of generating the appropriate arguments for the
BuildCookRun command or
BuildPlugin command and invoking UAT. Some example projects are listed below:
ue4cli: provides a command-line tool that automatically determines the correct path to the
RunUAThelper script and generates the appropriate arguments for building and packaging the project or plugin in the current working directory. The ue4-docker project includes ue4cli in the ue4-full container image.
ue4-ci-helpers: provides an API for scripting the build and packaging process for projects and plugins using Python code. Includes functionality for automatically producing compressed archives containing the packaged files. The ue4-docker project includes ue4-ci-helpers in the ue4-full container image.
In order to use any given infrastructure project it will need to be included in your container images. Unless your Unreal Engine container images already contain these components you will need to write a Dockerfile that extends an existing Unreal Engine container image and installs the desired infrastructure.
Building container images for deployment
In a scenario where you’re packaging a project for distribution via traditional mechanisms you will most likely start a container using an existing image and run a series of build commands inside that container. However, if you’re deploying a packaged project using Docker containers, the entire build process can actually take place within a docker build command that uses Docker multi-stage builds to copy the packaged files into a new container image at the end of the process. (In a dual-distribution scenario you can also copy the packaged files from the filesystem of the newly-built container image to the host filesystem and then deploy those files using traditional mechanisms.)
Writing a Dockerfile for a multi-stage build is quite straightforward:
The container image that contains the Engine Tools and that will be used for building and packaging the project should be specified in the first
FROMdirective of the Dockerfile.
This directive should be followed by one or more
RUNdirectives to build and package the project using your preferred mechanisms.
The Dockerfile should conclude with a second
FROMdirective that specifies the base image that the packaged project will run inside and a
COPYdirective to copy the packaged files into the new image.
An example Dockerfile is provided below that builds and packages a project in the ue4-full container image from the ue4-docker project and copies the packaged files into the adamrehn/ue4-runtime runtime image.
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