对于 docker 机器的用例，config.toml 中的 [runners.docker] 部分有什么用？

Question

正在阅读 documentation on autoscaling 当使用 docker+机器作为执行者时，我无法理解 [runner.docker] 部分的作用：

  [runners.docker]
    image = "ruby:2.1"               # The default image used for builds is 'ruby:2.1'

在 executors documentation 中说：

docker+machine : like docker, but uses auto-scaled docker machines - this requires the presence of [runners.docker] and [runners.machine]

我知道我必须定义这个 [runners.docker] 部分才能使用 [runners.machine] 部分，但是这个 [runners.docker] 的目的是什么？我找不到如何配置它，因为我不明白为什么要使用它。

我们的 gitlab-runner 在 vSphere VM 上运行，并配置为使用 docker+ 机器执行器和使用 vmwarevsphere 的 MachineDriver 进行扩展。一切正常，但我想完全理解配置文件。

这是我们的 "censored with stars" config.toml 文件，其中 [runners.docker] 我看不懂（注意写它的人离开了公司，所以我看不懂问他):

[[runners]]
  name = "gitlab-runner"
  limit = 6
  output_limit = 102400
  url = "http://gitlab.**************.lan"
  token = "*******************"
  executor = "docker+machine"

  [runners.docker]
    tls_verify = false
    image = "docker:latest"
    dns = ["*.*.*.*"]
    privileged = true
    disable_cache = false
    volumes = ["/etc/localtime:/etc/localtime:ro", "/var/run/docker.sock:/var/run/docker.sock", "/etc/docker/certs.d:/etc/docker/certs.d", "/cache:/cache", "/builds:/builds"]
    cache_dir = "cache"
    shm_size = 0

  [runners.cache]
    Type = "s3"
    ServerAddress = "*.*.*.*"
    AccessKey = "*****************"
    SecretKey = "*****************"
    BucketName = "runner"
    Insecure = true

  [runners.machine]
    IdleCount = 4
    MaxBuilds = 10
    IdleTime = 3600
    MachineDriver = "vmwarevsphere"
    MachineName = "gitlab-runner-pool-1-%s"
    MachineOptions = ["vmwarevsphere-username=************", "vmwarevsphere-password=*****************", "vmwarevsphere-vcenter=*.*.*.*", "vmwarevsphere-datastore=*********", "vmwarevsphere-memory-size=3096", "vmwarevsphere-disk-size=40960", "vmwarevsphere-cpu-count=3", "vmwarevsphere-network=*****************", "vmwarevsphere-datacenter=**************", "vmwarevsphere-hostsystem=*******************", "engine-storage-driver=overlay2", "engine-insecure-registry=**************", "engine-insecure-registry=*******************"]
    OffPeakPeriods = ["* * 0-8,21-23 * * mon-fri *", "* * * * * sat,sun *"]
    OffPeakTimezone = "Local"
    OffPeakIdleCount = 1
    OffPeakIdleTime = 600

Answer 1

[runners.machine] 部分定义了如何启动和配置 运行器机器，[runners.docker] 部分然后定义了如何配置runner在那台机器上。

Docker-机器本身仅执行以下操作（如您所见here）：

"Docker Machine is a tool that lets you install Docker Engine on virtual hosts, and manage the hosts with docker-machine commands."

所以这对 Gitlab runner 没有任何作用，之后你仍然需要配置 runner，这就是 [runners.docker] 部分发挥作用的地方，因为 runner 需要知道要使用的默认图像和体积安装等

对于 docker 机器的用例，config.toml 中的 [runners.docker] 部分有什么用？

What's the use of the [runners.docker] section in config.toml for use case with docker machine?

gitlab-ci

docker-machine

gitlab-ci-runner

vsphere

toml