How to use a custom windows docker container on gitlab-ci shared runner

i have a repository which consists of following two files, which builds an windows docker container with visual studio buildtools installed and pushes it to the registry provided by gitlab for my repository

./Dockerfile

# escape=`

FROM mcr.microsoft.com/windows/servercore:1809-amd64

RUN powershell mkdir .\TEMP\;`
    Invoke-WebRequest -Uri https://aka.ms/vs/16/release/vs_buildtools.exe -OutFile .\TEMP\vs_buildtools.exe; `
    .\TEMP\vs_buildtools.exe --quiet --wait --norestart --nocache `
    --installPath C:\BuildTools `
    --add Microsoft.VisualStudio.Component.VC.CMake.Project `
    --add Microsoft.VisualStudio.Component.VC.Tools.x86.x64 `
    --add Microsoft.VisualStudio.Component.Windows10SDK `
    --add Microsoft.VisualStudio.Component.Windows10SDK.18362


ENTRYPOINT ["C:\\BuildTools\\Common7\\Tools\\VsDevCmd.bat", "&&", "powershell.exe", "-NoLogo", "-ExecutionPolicy", "Bypass"]

./.gitlab-ci.yml

docker-build:  # Official docker image.
  tags: 
    - windows
  stage: build
  services:
    - docker:dind
  before_script:
    - docker login -u "$CI_REGISTRY_USER" -p "$CI_REGISTRY_PASSWORD" $CI_REGISTRY
  script:
    - docker build --pull -t "${CI_REGISTRY_IMAGE}:${CI_COMMIT_REF_SLUG}" .
    - docker push "${CI_REGISTRY_IMAGE}:${CI_COMMIT_REF_SLUG}"

so far this works perfectly

now in another repository i want to use this image to build my application on

./.gitlab-ci.yml

build-app:
  image: registry.gitlab.com/valerij/windows-builder:master
  tags: 
    - windows
  stage: build
  script:
    - "docker images"
    - "dir C:\\BuildTools" 
    - "cl --version"

which fails with

Running with gitlab-runner 13.4.1 (e95f89a0)
  on windows-shared-runners-manager Hs8mheX5
Preparing the "custom" executor
Using Custom executor with driver autoscaler dev (6184f4a)...
Creating virtual machine for the job...
Virtual machine created!
Preparing environment
00:11
Running on PACKER-5F1153D4 via 
runner-hs8mhex5-wsrm-4464870f601125122949...
Getting source from Git repository
Fetching changes with git depth set to 50...
Initialized empty Git repository in C:/GitLab-Runner/builds/valerij/ci-test/.git/
Created fresh repository.
Checking out f7535d50 as master...
git-lfs/2.8.0 (GitHub; windows amd64; go 1.12.2; git 30af66bb)
Skipping Git submodules setup
Executing "step_script" stage of the job script
WARNING: Starting with version 14.0 the 'build_script' stage will be replaced with 'step_script': https://gitlab.com/gitlab-org/gitlab-runner/-/issues/26426
$ docker images
REPOSITORY                             TAG                 IMAGE ID            CREATED             SIZE
mcr.microsoft.com/windows/servercore   ltsc2019            561b89eac394        7 months ago        3.7GB
$ dir C:\BuildTools
dir : Cannot find path 'C:\BuildTools' because it does not exist.
At line:1 char:1
+ dir C:\BuildTools
+ ~~~~~~~~~~~~~~~~~
    + CategoryInfo          : ObjectNotFound: (C:\BuildTools:String) [Get-ChildItem], ItemNotFoundException
    + FullyQualifiedErrorId : PathNotFound,Microsoft.PowerShell.Commands.GetChildItemCommand
 
Cleaning up file based variables
ERROR: Job failed: exit status 1

Now I notice that the log is missing anything along the lines familiar from another project

Pulling docker image node:latest ...
Using docker image sha256:2d840844f8e7594a542b30eaed0a3451f5d84b9f85d091d09abc8e0ae75c48e4 for node:latest with digest node@sha256:60a3bda0eb90be8fa78830f284671d4c231e91878bbe5bd1c953aedda141014a ...

It seems to me that the windows runner ignores the image keyword.

How do I force the windows runner to use my custom docker image to perform the CI in?

Solution

Short answer: you can't, but you might be able to work around it

Shared windows runners do not process image or services, so you can't set it that way. You should still be able to pull the other image and then execute commands / scripts inside it normally though.

e.g.,

build-app:
  tags: 
    - windows
  stage: build
  before_script:
    - docker login -u "$CI_REGISTRY_USER" -p "$CI_REGISTRY_PASSWORD" $CI_REGISTRY
  script:
    - "docker pull $CI_REGISTRY_IMAGE"
    - "docker images"
    - "docker run -v %cd%:%cd% -w %cd% $CI_REGISTRY_IMAGE cl --version"

You may need to adjust the mounts, path, etc. to your use case