Document how to build for Dedicated Server as the target platform

[webbertakken]

Context

As mentioned here it might be simple to do.

game-ci/unity-actions#136 (comment)

Suggested solution

Let's check if this works as expected and add it to the documentation

[AndrewKahr]

I don't think it will remain so simple to do. As stated in the initial post:

How can I access this new feature?
Dedicated Server platform support is now available inside the Unity Editor as of Unity 2021.2.0b1. Before 2021.3 LTS, Unity will move the feature from the default Unity Editor installation and into a separate support installer via Unity Hub in a future release.

Those support packages started appearing in 2021.2.4 and up so it seems like we need to install the support package for each platform you want to target for it to be an option. The support packages also seem to only be available to windows and mac hosts but both have support packages for windows, mac, and linux.

I also saw:

var buildPlayerOptions = new BuildPlayerOptions()
{
subtarget = (int) StandaloneBuildSubtarget.Server,
target = BuildTarget.StandaloneWindows64,
options = BuildOptions.Development
};

Not sure if this means the default build script needs updating.

[davidmfinol]

Before 2021.3 LTS, Unity will move the feature from the default Unity Editor installation and into a separate support installer via Unity Hub in a future release.

This reads to me as implying that 2021.3 LTS and newer will not require the support package. It sounds like we may need to do some extra work to support downloading the packages for Unity versions between 2021.2.0b1 and 2021.3 LTS, but I expect that the vast majority of users that are interested in server builds will stick to LTS versions.

var buildPlayerOptions = new BuildPlayerOptions()
{
subtarget = (int) StandaloneBuildSubtarget.Server,
target = BuildTarget.StandaloneWindows64,
options = BuildOptions.Development
};

This code is simply passing in the subtarget through code.
Currently, server builds can be done by passing EnableHeadlessMode through code or by passing EnableHeadlessMode through the Unity CLI.
We could update the default build script, but I think it would be better to encourage passing the subtarget through the Unity CLI if possible.

[AndrewKahr]

That's my bad, I got it backwards. We should be good then once documented.

[davidmfinol]

That's my bad, I got it backwards. We should be good then once documented.

It may be me who's reading it backwards. Either way, we'll find out once 2021.3 LTS is released.

[afroraydude]

This code is simply passing in the subtarget through code. Currently, server builds can be done by passing EnableHeadlessMode through code or by passing EnableHeadlessMode through the Unity CLI. We could update the default build script, but I think it would be better to encourage passing the subtarget through the Unity CLI if possible.

I had reported on your Discord (message link) that the flag does not work as of Unity 2021.2.27f1. I have preprocessor flags that run certain bits of code depending on if the application is running in server/headless mode (#UNITY_SERVER) that did work with the flag for 2021.2.26f1 but not 2021.27f1 or later. Thought I should put that out there. It has also been removed from the Unity documentation for 2021.2.

[davidmfinol]

@afroraydude Thanks for the confirmation on the CLI. Does it work if you set the subtarget in your buildMethod?

[afroraydude]

I'll test it out

[tliff]

I've tested it on 2021.2.12f1 by setting the subtarget in buildMethod.

Gives me

##### ExitCode
-1
##### Output
The properties of source file /opt/unity/Editor/Data/PlaybackEngines/LinuxStandaloneSupport/Variations/linux64_server_nondevelopment_mono/Data/Resources/unity default resources could not be retrieved: No such file or directory
[  2/131    0s] CopyFiles Builds/StandaloneLinux64Server/spacepirates
##### ExitCode
-1
##### Output
The properties of source file /opt/unity/Editor/Data/PlaybackEngines/LinuxStandaloneSupport/Variations/linux64_server_nondevelopment_mono/LinuxPlayer could not be retrieved: No such file or directory
[  3/131    0s] CopyFiles Builds/StandaloneLinux64Server/UnityPlayer.so
##### ExitCode
-1
##### Output
The properties of source file /opt/unity/Editor/Data/PlaybackEngines/LinuxStandaloneSupport/Variations/linux64_server_nondevelopment_mono/UnityPlayer.so could not be retrieved: No such file or directory
*** Tundra build failed (0.15 seconds), 129 items updated, 131 evaluated

which seems to imply that the support modules (windows-server/linux-server/mac-server) are required.

[paulpach]

I was got the same error as @tliff by setting the subtarget

Please see my pull request, it should add the missing modules so that the images can now build dedicated servers

[davidmfinol]

The images should be created when the next docker version is released.
We also need to update unity-builder to set the subtarget, and test using the new images.

[jbarnoin]

Hey,

As per the above, it looks like dedicated server build support is supposed to be available in the latest linux docker images, however our build is failing with "Error building Player: Currently selected scripting backend (Mono) is not installed." when trying to build using unityci/editor:2021.3.4f1-base-1.0.1, only if our build script contains
EditorUserBuildSettings.standaloneBuildSubtarget = StandaloneBuildSubtarget.Server;

Without this subtarget the build works fine. I've confirmed that this is the same error I get if I try building locally with this subtarget without the dedicated server module installed, and that it goes away after adding the submodule.

Is there any chance the images somehow don't yet have the dedicated server module installed? Otherwise any clue about what might be causing the error will be appreciated.

[Thendon]

@jbarnoin encountered this issue as well. After reading through the Dockerfile I realized that only docker images which include the string "linux" contain the linux-server module what kind of makes sense. The only image which contains linux is linux-il2cpp though. So I changed the gitlab-ci.yml to
image: $IMAGE:$UNITY_VERSION-linux-il2cpp-$IMAGE_VERSION

Does that mean there is no image for building linux server with mono or did I overlook something?