How to run etcd cluster in docker using ansible?

Question

I'm trying to run etcd cluster in docker via ansible.

I use docker_container ansible module and this is what I have:

- name: Run etcd KV node
      docker_container:
        name: "etcd0"
        image: quay.io/coreos/etcd
        network_mode: host
        command: [ "/usr/local/bin/etcd", \
        "-name etcd0", \
        "-advertise-client-urls http://{{ ansible_default_ipv4['address'] }}:2379,http://{{ ansible_default_ipv4['address'] }}:4001", \
        "-listen-client-urls http://0.0.0.0:2379,http://0.0.0.0:4001", \
        "-initial-advertise-peer-urls http://{{ ansible_default_ipv4['address'] }}:2380", \
        "-initial-cluster etcd0=http://{{ ansible_default_ipv4['address'] }}:2380", \
        "-initial-cluster-token etcd-cluster", \
        "-listen-peer-urls http://0.0.0.0:2380", \
        "-initial-cluster-state new" ]

This work in single mode, but troubles come with more than 1 node because there is etcd parameter -initial-cluster which should contain all nodes, for example, in case of 3 nodes:

-initial-cluster etcd0=http://192.168.12.50:2380,etcd1=http://192.168.12.51:2380,etcd2=http://192.168.12.52:2380

I have no idea how to loop thru all nodes and build this string to run one docker container. Is it possible?

Answer 1

hostvars magic variable at your service:

- name: Generate useful facts for current node 1
  set_fact:
    ip_addr: "{{ ansible_default_ipv4.address }}"
    etcd_name: "etcd{{ ansible_play_hosts.index(inventory_hostname) }}"

- name: Generate useful facts for current node 2
  set_fact:
    etcd_uri: "{{ etcd_name }}=http://{{ ip_addr }}:2380"

- name: Run etcd KV node
  docker_container:
    name: "{{ etcd_name }}"
    image: quay.io/coreos/etcd
    network_mode: host
    command:
      - /usr/local/bin/etcd
      - -name {{ etcd_name }}
      - -advertise-client-urls http://{{ ip_addr }}:2379,http://{{ ip_addr }}:4001
      - -listen-client-urls http://0.0.0.0:2379,http://0.0.0.0:4001
      - -initial-advertise-peer-urls http://{{ ip_addr }}:2380
      - -initial-cluster {{ ansible_play_hosts | map('extract',hostvars,'etcd_uri') | list | join(',') }}
      - -initial-cluster-token etcd-cluster
      - -listen-peer-urls http://0.0.0.0:2380
      - -initial-cluster-state new

P.S. I also reformatted your command argument a bit.