Unreal Horde Source Build Documentation with ARM64 Support #813

cwwalb · 2025-12-13T01:02:51Z

Issue number:
closes #743

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hwkiem

Great PR. A few minor changes and a couple discussions for the team.

hwkiem · 2025-12-17T17:11:01Z

modules/unreal/horde/ecs.tf

+      }, var.github_credentials_secret_arn != null && !var.is_source_build ? {
+      repositoryCredentials = {
+        "credentialsParameter" : var.github_credentials_secret_arn
+      }
+      } : {}, {


Could move some of this logic to a local

hwkiem · 2025-12-17T17:11:32Z

modules/unreal/horde/ecs.tf

    {
      name                     = "unreal-horde-docdb-cert",
-      image                    = "public.ecr.aws/docker/library/bash:5.3",
+      image                    = "public.ecr.aws/docker/library/bash:latest",


It is probably safer to pin to a specific version of bash. :latest opens us up to upstream issues

I know we do this elsewhere... probably should open an issue and fix those too.

hwkiem · 2025-12-17T17:12:22Z

modules/unreal/horde/ecs.tf

    local.need_p4_trust ? [{
      name      = "unreal-horde-p4-trust",
-      image     = "ubuntu:noble"
+      image     = "public.ecr.aws/ubuntu/ubuntu:noble"


nice fix. I wonder if we should also pin this release to a particular version for the same reason as above.

hwkiem · 2025-12-17T17:12:54Z

modules/unreal/horde/source-build/README.md

Do you think we should put this in a nested directory like this? Or just update the Horde README with these instructions?

hwkiem · 2025-12-17T17:16:00Z

modules/unreal/horde/source-build/README.md

+### For devices using ARM64 architecture
+1. In an IDE, open the Horde Server Dockerfile located at `/Engine/Source/Programs/Horde/HordeServer/Dockerfile`.
+2. Replace the code between `COPY --from=redis /usr/local/bin/redis-server /usr/local/bin/redis-server` and `COPY Source/Programs/Shared/EpicGames.Core/*.csproj ./Source/Programs/Shared/EpicGames.Core/` with the following:
+
+    ```dockerfile
+    # Since the .deb does not install in this image, just download it and extract the static binary
+    RUN ARCH=$(dpkg --print-architecture) && \
+        if [ "$ARCH" = "arm64" ]; then \
+            wget https://repo.mongodb.org/apt/ubuntu/dists/jammy/mongodb-org/7.0/multiverse/binary-arm64/mongodb-org-server_7.0.4_arm64.deb && \
+            dpkg -x mongodb-org-server_7.0.4_arm64.deb /tmp/mongodb; \
+        else \
+            wget https://repo.mongodb.org/apt/debian/dists/bookworm/mongodb-org/7.0/main/binary-amd64/mongodb-org-server_7.0.4_amd64.deb && \
+            dpkg -x mongodb-org-server_7.0.4_amd64.deb /tmp/mongodb; \
+        fi && \
+        cp /tmp/mongodb/usr/bin/mongod /usr/local/bin/mongod
+    ```
+3. Locate the code block with the comment `# Remove native libs not used on Linux x86_64`. We need to modify this so that the build has the libraries associated with the operating system and CPU architecture we are using. To do this, replace that block with the following:
+```dockerfile
+# Remove native libs not used for current architecture
+RUN ARCH=$(dpkg --print-architecture) && \
+    if [ "$ARCH" = "amd64" ]; then \
+        rm -rf /app/out/runtimes/osx* && \
+        rm -rf /app/out/runtimes/win-x86 && \
+        rm -rf /app/out/runtimes/win-arm* && \
+        rm -rf /app/out/runtimes/linux-arm* && \
+        rm -rf /app/out/runtimes/linux-x86 && \
+        rm -rf /app/out/runtimes/linux/native/libgrpc_csharp_ext.x86.so; \
+    elif [ "$ARCH" = "arm64" ]; then \
+        rm -rf /app/out/runtimes/osx-x64 && \
+        rm -rf /app/out/runtimes/win-x64 && \
+        rm -rf /app/out/runtimes/win-x86 && \
+        rm -rf /app/out/runtimes/linux-x64* && \
+        rm -rf /app/out/runtimes/linux-x86 && \
+        rm -rf /app/out/runtimes/linux/native/libgrpc_csharp_ext.x64.so && \
+        rm -rf /app/out/runtimes/linux/native/libgrpc_csharp_ext.x86.so; \
+    fi
+```


What in the WORLD is going on here? Why are we removing the redis dependencies? I am confusion.

This was the original code from the UE repository

# Remove native libs not used on Linux x86_64 RUN rm -rf /app/out/runtimes/osx* && \ rm -rf /app/out/runtimes/win* && \ rm -rf /app/out/runtimes/linux-arm* && \ rm -rf /app/out/runtimes/linux/native/libgrpc_csharp_ext.x86.so

It seems to be removing libs that are not used for the Linux x86_64 because that is the architecture this is built for by default. I think this is to remove unnecessary libraries to remove bloat from the docker image. In order to follow this same principle we make this compatible with all compute architectures and OS by identifying the architecture and OS the build is for, then removing the other libraries.

hwkiem · 2025-12-17T17:20:25Z

modules/unreal/horde/source-build/README.md

+        <Docker-Build BaseDir="Engine/Source/Programs/Horde/HordeServer" Files="Dockerfile*" UseBuildKit="true" Tag="horde-server" DockerFile="Engine/Source/Programs/Horde/HordeServer/Dockerfile.dashboard" />
+
+        <!-- Publish the docker image to Amazon ECR -->
+        <Docker-Push Repository="<account-id>.dkr.ecr.<region>.amazonaws.com" Image="horde-server" TargetImage="horde/horde-server:$(Version)" AwsEcr="True" />


I do like this... Just wondering if we want to recommend the creation of a new graph. I wonder if you could raise a PR against the the engine itself with modifications / improvements to the Horde buildgraph.

I agree also would make sense to do the same with the Horde Server Dockerfile since at the moment it only is designed to support AMD64 and I have the fixes to make it more adaptive to the different architectures which you see in the README

hwkiem · 2025-12-17T17:21:59Z

modules/unreal/horde/source-build/README.md

+1. In your IDE, open the main.tf located at `modules/unreal/horde/examples/complete/main.tf`.
+2. Under the module declaration `"unreal_engine_horde"` add the following line with the value of the image URI you noted earlier. Be sure to also set the value of `is_source_build` to `true` and set the value of `horde_server_architecture` to `ARM64` or `X_86` by passing the value with the `var.horde_server_architecture` variable as shown below:
+    ```python
+    module "unreal_engine_horde" {
+        ...
+        image = "<image-uri>"
+        is_source_build = true
+        horde_server_architecture = "<horde-server-architecture>"
+        ...
+    }
+    ```


We should manage this through variables on the example.

hwkiem · 2025-12-17T17:23:50Z

modules/unreal/horde/variables.tf

+variable "horde_server_architecture" {
+  type        = string
+  description = "The CPU architecture for Horde server container. Valid values: x86 or arm64"
+  default     = "X86_64"
+  validation {
+    condition     = contains(["X86_64", "ARM64"], var.horde_server_architecture)
+    error_message = "horde_server_architecture must be either 'X_86' or 'ARM64'"
+  }
+}


Can we determine architecture via data block and a lookup against the image?

hwkiem · 2025-12-17T17:24:15Z

modules/unreal/horde/variables.tf

+variable "is_source_build" {
+  type        = bool
+  description = "Set this flag to true if you are using a custom built Horde Server image from source."
+  default     = false
+}


Why do we need to know if its a source build?

I added that because in ecs.tf we have the current steps to use github credentials as part of the container definition to pull the public horde docker image. I didn't want to break the functionality so created the variable so the user can still use the pre-built docker image if they choose or go for the source build

hwkiem · 2025-12-17T17:28:49Z

modules/unreal/horde/variables.tf

+variable "operating_system" {
+  type        = string
+  description = "The operating system for the Horde server container. Valid values: linux or windows"
+  default     = "WINDOWS_SERVER_2019_CORE"
+  validation {
+    condition     = contains(["LINUX", "WINDOWS_SERVER_2025_FULL", "WINDOWS_SERVER_2025_CORE", "WINDOWS_SERVER_2022_FULL", "WINDOWS_SERVER_2022_CORE", "WINDOWS_SERVER_2019_FULL", "WINDOWS_SERVER_2019_CORE"], var.operating_system)
+    error_message = "Operating_system must be either LINUX, WINDOWS_SERVER_2025_FULL, WINDOWS_SERVER_2025_CORE, WINDOWS_SERVER_2022_FULL, WINDOWS_SERVER_2022_CORE, WINDOWS_SERVER_2019_FULL, and WINDOWS_SERVER_2019_CORE."
+  }
+}


Also this. I am not sure why we want to support a windows OS for Horde unless a customer explicitly asks for it. Open to your thoughts on this!

That was something I wanted to ask. What are the most commonly used OS for Horde?

github-actions · 2025-12-19T21:39:19Z

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github-actions · 2025-12-19T21:39:47Z

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cwwalb self-assigned this Dec 13, 2025

cwwalb force-pushed the cwwalb/ue-horde-source-build branch 3 times, most recently from b78cc1d to 44ff5cb Compare December 15, 2025 16:28

cwwalb changed the title ~~Unreal Horde Source Build Documentation with ARM64 Support~~ Unreal Horde Source Build Documentation with ARM64 Support (#743) Dec 15, 2025

cwwalb changed the title ~~Unreal Horde Source Build Documentation with ARM64 Support (#743)~~ Unreal Horde Source Build Documentation with ARM64 Support Dec 15, 2025

hwkiem requested changes Dec 17, 2025

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cwwalb force-pushed the cwwalb/ue-horde-source-build branch from 44ff5cb to f1986bd Compare December 19, 2025 21:38

cwwalb force-pushed the cwwalb/ue-horde-source-build branch from f1986bd to dea95d5 Compare December 19, 2025 21:56

docs: Unreal Horde source build instructions

a4fd601

cwwalb force-pushed the cwwalb/ue-horde-source-build branch from dea95d5 to a4fd601 Compare December 19, 2025 21:59

Unreal Horde Source Build Documentation with ARM64 Support #813

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