Interactive Web Terminal and Docker Machine runner possible?

Hey everyone

We are using Docker Machine runner to autoscale VM runners in the cloud. I am now trying to set things up for using the interactive web terminal. On a standard docker/shell runner in the cloud that only runs on one VM the debug shell opens up as expected, but if I want to open the terminal for a job running on the docker machine runner it doesn’t work.

I just see an empty black window for 10 minutes or so and then I see “Connection failure”.

Gitlab version: Gitlab.com SaaS (14.4.0-pre)
Runner: Docker machine runner

I don’t fully understand how the feature actually works from the documentation and in absence of any logs I can’t really debug this.

Is this feature even supported for the runner I am using?
Looking at the compatibility matrix I am unsure.

So Gitlab Runner opens up the port 8093 on the VM that doesn’t actually run the job but provisions the VM dynamically that will run the job, how can I configure this in order for the shell terminal to actually be able to connect to the docker container on the host that runs the job?

Runner Config:

concurrent = 10
check_interval = 0
[session_server]
  session_timeout = 1800
  listen_address = "[::]:8093"
  advertise_address = "PUBLIC_IP_OF_RUNNER_VM:8093"
[[runners]]
  name = "RUNNER_NAME"
  url = "https://gitlab.com/"
  token = "TOKEN"
  executor = "docker+machine"
  environment = ["DOCKER_DRIVER=overlay2", "DOCKER_TLS_CERTDIR="]
  [runners.cache]
    Type = "gcs"
    Shared = true
    [runners.cache.gcs]
      CredentialsFile = "FILE"
      BucketName = "BUCKETNAME"
  [runners.docker]
    tls_verify = false
    image = "alpine:latest"
    privileged = true
    disable_entrypoint_overwrite = false
    oom_kill_disable = false
    disable_cache = false
    volumes = ["/var/run/docker.sock:/var/run/docker.sock", "/cache"]
    pull_policy = "always"
    shm_size = 0
  [runners.machine]
    IdleCount = 1
    IdleTime = 3600
    MaxBuilds = 100
    MachineDriver = "google"
    MachineName = "MACHINE_NAME"
    MachineOptions = [SOME_MACHINE_OPTIONS]
    OffPeakPeriods = ["* * 0-7,18-0 * * mon-fri *", "* * * * * sat,sun *"]
    OffPeakTimezone = ""
    OffPeakIdleCount = 0
    OffPeakIdleTime = 3600