Gitlab-CI cannot connect to services on windows based containers

Hi Gitlab community

I’m currently migrating our CI/CD pipeline from a Bitbucket/Jenkins environment to hosted GitLab with additional custom gitlab-ci runners. So far anything seems fine, except when it comes down to services, especially regarding MSSQL server.

I’ve setup a gitlab-ci.yml file, which contains a service and a build stage job which basically just executes some msbuild targets.
I call the AttachDatabase target which then internally connects to the database and prepares anything for unittesting. Unfortunately I’m not able to connect to the database, whether I alias the service or not.

According to the documentation, I should just be able to use the alias name defined in services in my connection string found in Library.Build.Database.targets to connect to the databse.

I’ve setup a small reference project which ilustrates the problem: mssql-test.
If the pipeline is run the following error message is shown in the log:

error : A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections

I’m running a custom windows Gitlab runner (just for performance reasons), below the according config.toml

    concurrent = 1
check_interval = 0

  session_timeout = 1800

  name = "gitlab-runner-02-windows-server-datacenter-1809"
  url = ""
  token = "****"
  executor = "docker-windows"
    tls_verify = false
    image = ""
    privileged = false
    disable_entrypoint_overwrite = false
    oom_kill_disable = false
    disable_cache = false
    volumes = ["c:\\cache"]
    shm_size = 0

Any ideas what I’m missing?

Cheers Lukas