Running an Ansible command in multiple docker containers

Solution 1:

Given the following example output from docker ps:

$ docker ps
CONTAINER ID        IMAGE               COMMAND                  CREATED             STATUS              PORTS               NAMES
7e21761c9c44        busybox             "top"                    22 minutes ago      Up 22 minutes                           agitated_yonath
7091d9c7cc56        nginx               "nginx -g 'daemon off"   23 minutes ago      Up 23 minutes       80/tcp, 443/tcp     fervent_blackwell

This playbook will give you an idea of how to capture the data you need and how to run actions iterating on the provided list. It's a very simple example, and you'll have to adapt it to your needs. That's on purpose:

---
- hosts: localhost
  gather_facts: no
  tasks:

  - name: gather list of containers
    shell: docker ps | awk '/{{ item }}/{print $1}'
    register: list_of_containers
    with_items:
      - busybox

  #- name: debug
  #  debug: msg="{{ list_of_containers }}"

  - name: run action in container(s)
    docker_container:
      name: temp-container
      image: busybox
      command: uptime
      cleanup: yes
      detach: yes
    register: result_of_action
    with_items:
      - list_of_containers.results.stdout_lines

The interesting parts are:

1. Gather the list of containers in a given host (localhost in my example). I've used a plain shell invocation to be able to use awk to filter out the output. The result is stored in a register. Since the input is a list, this will have a direct consequence on how to retrieve the data back, more below. Uncomment the debug task in between to compare the data stored in the register with and without a list.

2. Iterate over the register's results (container ID) and use the docker_container module to run an action (command parameter). You can use links and volumes_from in your docker_container invocation. Check the on-line documentation of the module for the details.