Ansible Role: Docker Swarm

Setup a Docker Swarm cluster on RHEL/CentOS and Debian/Ubuntu servers using the new Docker Engine's "Swarm Mode" (https://docs.docker.com/engine/swarm/).

Requirements

None.

Role Variables

Available variables are listed below, along with default values (see defaults/main.yml):

docker_repo: main
# docker_repo: testing
# docker_repo: experimental

The repo from which install Docker. Override the default to install testing or experimental docker builds.

docker_dependencies: "{{ default_docker_dependencies }}"

Extra packages that have to installed together with Docker. The value of default_docker_dependencies depends on the target OS family.

NB: If you are installing Docker on a Raspberry running Raspbian or any other Debian-like OS make sure to set docker_dependencies: [ ] otherwise Ansible will fail because the linux-image-extra-virtual package is not available for the arm architecture (see issue #4).

docker_swarm_interface: "{{ ansible_default_ipv4['alias'] }}"

Setting docker_swarm_interface allows you to define which network interface will be used for cluster inter-communication.

docker_swarm_addr: "{{ hostvars[inventory_hostname]['ansible_' + docker_swarm_interface]['ipv4']['address'] }}"

Docker manager IP address is resolved at runtime by default. Settings docker_manager_address allows to set specific address.

By default, the ip address for raft API will be taken from desired interface. You can setup listening address where the raft APIs will be exposed, overriding the docker_swarm_addr variable value in your playbook.

docker_swarm_port: 2377

Listening port where the raft APIs will be exposed.

docker_admin_users:
  - "{{ ansible_user }}"

The list of users that has to be added to the docker_group to interact with the Docker daemon. NB: The users must already exist in the system.

skip_engine: False
skip_group: False
skip_swarm: False
skip_docker_py: False

Setting skip_engine: True will make the role skip the installation of docker-engine. If you want to use this role to just install docker-engine without enabling swarm-mode set skip_swarm: True. To skip the tasks adding the docker_admin_users to the docker_group set skip_group: True. Finally, the docker-py installation task can be skipped setting skip_docker_py to True.

Swarm node labels

Node labels provide a flexible method of node organization. You can also use node labels in service constraints. Apply constraints when you create a service to limit the nodes where the scheduler assigns tasks for the service. You can define labels by swarm_labels variable, e.g:

$ cat inventory
...
[docker_swarm_manager]
swarm-01 swarm_labels=deploy

[docker_swarm_worker]
swarm-02 swarm_labels='["libvirt", "docker", "foo", "bar"]'
swarm-03
...

In this case:

$ docker inspect --format '{{json .Spec.Labels}}'  swarm-02 | jq
{
   "bar": "true",
   "docker": "true",
   "for": "true",
   "libvirt": "true",
}

You can assign labels to cluster running playbook with --tags=swarm_labels

NB: Please note, all labels that are not defined in inventory will be removed

Dependencies

None.

Example Playbook

$ cat inventory
swarm-01 ansible_ssh_host=172.10.10.1
swarm-02 ansible_ssh_host=172.10.10.2
swarm-03 ansible_ssh_host=172.10.10.3

[docker_engine]
swarm-01
swarm-02
swarm-03

[docker_swarm_manager]
swarm-01 swarm_labels=deploy

[docker_swarm_worker]
swarm-02 swarm_labels='["libvirt", "docker", "foo", "bar"]'
swarm-03

$ cat playbook.yml
- name: "Provision Docker Swarm Cluster"
  hosts: all
  roles:
    - { role: atosatto.docker-swarm }

License

MIT

Author Information

Andrea Tosatto (@_hilbert_)