A customized Docker image for running scalable GitLab CI runners on DC/OS via Marathon.

The GitLab runner can be configured by environment variables. For a complete overview, have a look at the docs/gitlab_runner_register_arguments.md file.

The most important ones are:

• GITLAB_SERVICE_NAME: The Mesos DNS service name of the GitLab instance, e.g. gitlab.marathon.mesos. This strongly depends on your setup, i.e. how you launched GitLab and how you configured Mesos DNS. This is the recommended method to use with DC/OS installations of GitLab. Either this environment variable or GITLAB_INSTANCE_URL is mandatory.
• GITLAB_INSTANCE_URL: The URL of the GitLab instance to connect to, e.g. http://gitlab.mycompany.com. Either this environment variable or GITLAB_SERVICE_NAME is mandatory.
• REGISTRATION_TOKEN: The registration token to use with the GitLab instance. See the docs for details. (mandatory)
• RUNNER_EXECUTOR: The type of the executor to use, e.g. shell or docker. See the executor docs for more details. (mandatory)
• RUNNER_CONCURRENT_BUILDS: The number of concurrent builds this runner should be able to handel. Default is 1.
• RUNNER_TAG_LIST: If you want to use tags in you .gitlab-ci.yml, then you need to specify the comma-separated list of tags. This is useful to distinguish the runner types.

Private Docker registries can be used by adding the secret variable DOCKER_AUTH_CONFIG to your project's Settings ➔ CI/CD Pipelines settings. Have a look at the guide as well.

This version of the GitLab CI runner for Marathon project uses Docker-in-Docker techniques, with all of its pros and cons. See also jpetazzo's article on this topic.

In the following examples, we assume that you're running the GitLab Universe package as service gitlab on the DC/OS internal Marathon instance, which is also available to the runners via the external_url of the GitLab configuration. This normally means that GitLab is exposed on a public agent node via marathon-lb. Please see the [example documentation here|https://github.com/dcos/examples/tree/master/1.8/gitlab].

An example for a shell runner. This enables the build of Docker images.

{
  "id": "gitlab-runner-shell",
  "container": {
    "type": "DOCKER",
    "docker": {
      "image": "tobilg/gitlab-ci-runner-marathon:v13.4.1",
      "network": "HOST",
      "forcePullImage": true,
      "privileged": true
    }
  },
  "instances": 1,
  "cpus": 1,
  "mem": 2048,
  "env": {
    "GITLAB_SERVICE_NAME": "gitlab.marathon.mesos",
    "REGISTRATION_TOKEN": "zzNWmRE--SBfeMfiKCMh",
    "RUNNER_EXECUTOR": "shell",
    "RUNNER_TAG_LIST": "shell,build-as-docker",
    "RUNNER_CONCURRENT_BUILDS": "4"
  },
  "taskKillGracePeriodSeconds": 15,
  "healthChecks": [
     {
       "path": "/metrics",
       "portIndex": 0,
       "protocol": "HTTP",
       "gracePeriodSeconds": 300,
       "intervalSeconds": 60,
       "timeoutSeconds": 20,
       "maxConsecutiveFailures": 3,
       "ignoreHttp1xx": false
     }
  ]
}

Here's an example for a Docker runner, which enables builds inside Docker containers:

{
  "id": "gitlab-runner-docker",
  "container": {
    "type": "DOCKER",
    "docker": {
      "image": "tobilg/gitlab-ci-runner-marathon:v13.4.1",
      "network": "HOST",
      "forcePullImage": true,
      "privileged": true
    }
  },
  "instances": 1,
  "cpus": 1,
  "mem": 2048,
  "env": {
    "GITLAB_SERVICE_NAME": "gitlab.marathon.mesos",
    "REGISTRATION_TOKEN": "zzNWmRE--SBfeMfiKCMh",
    "RUNNER_EXECUTOR": "docker",
    "RUNNER_TAG_LIST": "docker,build-in-docker",
    "RUNNER_CONCURRENT_BUILDS": "4",
    "DOCKER_IMAGE": "node:6-wheezy"
  },
  "taskKillGracePeriodSeconds": 15,
  "healthChecks": [
     {
        "path": "/metrics",
        "portIndex": 0,
        "protocol": "HTTP",
        "gracePeriodSeconds": 300,
        "intervalSeconds": 60,
        "timeoutSeconds": 20,
        "maxConsecutiveFailures": 3,
        "ignoreHttp1xx": false
      }
  ]
}

Make sure you choose a useful default Docker image via DOCKER_IMAGE, for example if you want to build Node.js projects, the node:6-wheezy image. This can be overwritten with the image property in the .gitlab-ci.yml file (see the GitLab CI docs.

An .gitlab-ci.yml example of using the build-as-docker tag to trigger a build on the runner(s) with shell executors:

stages:
  - ci

build-job:
  stage: ci
  tags:
    - build-as-docker
  script:
    - docker build -t tobilg/test .

This assumes your project has a Dockerfile, for example

FROM nginx

An .gitlab-ci.yml example of using the build-in-docker tag to trigger a build on the runner(s) with Docker executors:

image: node:6-wheezy

stages:
  - ci

test-job:
  stage: ci
  tags:
    - build-in-docker
  script:
    - node --version