Building #SpigotMC in a Windows #Container using #Docker (#WindowsContainer)

When I started working on a Windows container for my Minecraft server, I realized that my installation was also in dire need of an update to the latest version of SpigotMC. This does not come as a source release so it needs to be compiled manually. Therefore, I investigated how the build process can be banished into a container. Here is how it is done!

SpigotMC offers a very detailed guide how to build the SpigotMC Minecraft server from source. The developers have automated this process and provide it in a JAR called BuildTools.jar which must be downlaoded from the website. These build tools require a Java Runtime Environment and a Git installation.

I have created an image with all the prerequisites which is created using the following Dockerfile and my java docker image:

FROM nicholasdille/javaruntime:8u91
MAINTAINER nicholas.dille@mailbox.org

ADD https://github.com/git-for-windows/git/releases/download/v2.9.0.windows.1/Git-2.9.0-64-bit.exe c:\Git-2.9.0-64-bit.exe
RUN c:\Git-2.9.0-64-bit.exe /SILENT
RUN del c:\Git-2.9.0-64-bit.exe

RUN md c:\build
ADD RunBuildTools.ps1 c:\build
ADD https://hub.spigotmc.org/jenkins/job/BuildTools/lastSuccessfulBuild/artifact/target/BuildTools.jar /build/BuildTools.jar

CMD powershell -command c:\build\RunBuildTools.ps1

As soon as a container is launched based on this image, the build tools are launched automatically by the PowerShell script called RunBuildTools.ps1:

$Env:JAVA_HOME = "$Env:ProgramFiles\Java\jre1.8.0u91"
$Env:Path = "$Env:Path;$Env:ProgramFiles\Git\bin;$JAVA_HOME\bin"

Set-Location -Path c:\build
java.exe -jar BuildTools.jar

Note that the build succeeds although it is not launched from git-bash. Apparently PowerShell comes with the necessary aliases to resemble bash closely enough.

For my as well as your convenience, I have created a wrapper script for launching the container (docker run) and waiting for the build to complete (docker wait). After displaying the last five lines the script extracts the name of the resulting JAR file and copies it to the current directory (docker cp).

@Echo Off

docker run -d --name build nicholasdille/spigotmc-build
docker wait build
docker logs --tail=5 build

for /f "usebackq tokens=4" %%i in (`docker logs --tail=1 build`) do docker cp build:c:\build\%%i .

I have also published all the source shown above in my GitHub repository for docker as well as published the resulting image in Docker Hub as nicholasdille/spigotmc-build.