Ansible: copy files to Docker Volume - docker

Question

I run a Ansible Playbook that gathers machine specific information and store the date within a file. One for each host. So I end up with a buch of files which should now be send to my Docker-Based Application for further processing.
Actuall I need to store it in a specific folder and create a volume so the container is able to read the files.
This requires the existence/creation of /tmp/incoming ...
Now if the Monitor app gets moved or a second Instance is needed, you'll have to access the filesystem and create the dirctory.
So I'd like to create a more dynamic volume:
docker volume create --name monitor-incoming:/var/www/monitor/incoming
Now Docker containers will be able to access the volume. But can I use Ansible to "copy" the files to this remote volume ? Sending them to monitor-incoming instead of /tmp/incoming ?

Answer 1

You could use any of the following methods:
Ansible non-SSH docker connection with standard Ansible file/copy modules. Example taken from from Ansible documentation:
- name: create jenkins container
docker_container:
docker_host: myserver.net:4243
name: my_jenkins
image: jenkins
- name: add container to inventory
add_host:
name: my_jenkins
ansible_connection: docker
ansible_docker_extra_args: "--tlsverify --tlscacert=/path/to/ca.pem --tlscert=/path/to/client-cert.pem --tlskey=/path/to/client-key.pem -H=tcp://myserver.net:4243"
ansible_user: jenkins
changed_when: false
- name: create directory for ssh keys
delegate_to: my_jenkins
file:
path: "/var/jenkins_home/.ssh/jupiter"
state: directory
Ansible command module using the docker cli. I have had more success with this method.
- name: remove temporary data-only container
become: yes
docker_container:
name: your_temp_data_container
state: absent
- name: recreate data volume
become: yes
docker_volume:
name: your_data_volume
state: present
- name: create temporary data-only container
become: yes
docker_container:
name: your_temp_data_container
image: tianon/true
state: present
volumes:
- your_data_volume:/data
- name: copy folder contents to data volume via temporary data-only container
become: yes
command: docker cp /some_data_path_on_this_ansible_host/. your_temp_data_container:/data
- name: remove temporary data-only container
become: yes
docker_container:
name: your_temp_data_container
state: absent

Answer 2

I don't have a docker environment to test this out, but I think you could do it from the host with a docker run on a bash image that:
Binds the host's directory in which the file you want to copy is (I assumed we are copying /path/to/filename/on/host). I bound that directory to /tmp/source/ inside the container.
Binds the monitor-incoming volume somewhere in the container. I chose to bind it to /tmp/destination/.
Runs a simple cp command (since the entrypoint of the bash image is bash itself, we just have to add the command to run).
Here is the command:
docker run \
--mount source=monitor-incoming,target=/tmp/destination \
--mount type=bind,source=/path/to/filename/on/host,target=/tmp/source \
bash:4.4 \
cp "/tmp/source" "/tmp/destination/path/to/destination/inside/volume/"
This is not tested, but I think something along those lines should work. Notice that if that script is used fairly frequently, you should probably have a container dedicated to that task rather than call docker run many times.
I'm not sure if there's a more direct way that would not involve running cp inside a container...

Answer 3

I wish we could do it with a built-in module, but unless we have one, you can add a file into a named volume in a single task:
- name: actual config file is in the volume
command:
cmd: docker run --rm -iv your-config-volume:/v busybox sh -c 'cat > /v/config.yml'
stdin: "{{ lookup('file', 'config.yml') | regex_replace('\\r\\n', '\\n') }}"
Here we use command module to create a temporary container with the your-config-volume volume attached.
The sh -c 'cat > /v/config.yml' command saves all stdin into a file.
Finally, we set stdin to be the config.yml file from your role.
The regex_replace('\\r\\n', '\\n') part is required only if you run Windows.