docker.json

{
    "variables": {
        "project_id": null,
        "source_image_family": "ubuntu-1604-lts",
        "image_family": "docker-base",
        "machine_type": "f1-micro",
        "zone": "europe-west1-d",
        "disk_size": "10",
        "disk_type": "pd-standard",
        "network": "default",
        "subnetwork": "",
        "tags": "",
        "playbook_name": "docker.yml"
    },
    "builders": [
        {
            "type": "googlecompute",
            "project_id": "{{user `project_id`}}",
            "image_name": "{{user `image_family`}}-{{timestamp}}",
            "image_family": "{{user `image_family`}}",
            "source_image_family": "{{user `source_image_family`}}",
            "zone": "{{user `zone`}}",
            "ssh_username": "appuser",
            "machine_type": "{{user `machine_type`}}",
            "image_description": "gitlab-docker base image",
            "disk_size": "{{user `disk_size`}}",
            "disk_type": "{{user `disk_type`}}",
            "network": "{{user `network`}}",
            "subnetwork": "{{user `subnetwork`}}",
            "tags": "{{user `tags`}}"
        }
    ],
    "provisioners": [
        {
            "type": "ansible",
            "playbook_file": "ansible/playbooks/{{user `playbook_name`}}",
            "ansible_env_vars": [
                "ANSIBLE_ROLES_PATH=./ansible/roles_imported:./ansible/roles"
            ]
        }
    ]
}