Using Ansible docker_container, how can I display standard out? (stdout)

Question

I'm using Ansible and its module docker_container to launch tape unit test containers in nodejs. This is nice because I don't have to have npm mess up my host, my only dev box dependency is python and docker.

I need to be able to see stdout to see that tests have been run. However, Docker's --attach option is not exposed in docker_container and I cannot find any way to have stdout print out from the ansible launch of the container.

I can go back to bash scripts to launch docker containers but I'd rather not...

How can I display a container's standard out with Ansible's docker_container module?

Answer 1

This actually works with Ansible v2.5, by using the detach attribute:

- name: Run the tests
  docker_container:
    detach: false
    name: "foo-container"
    command: npm test
  register: docker_container_output

- name: Show test output
  debug:
    msg: "{{ docker_container_output.ansible_facts.docker_container.Output }}"

- name: Remove the test container
  docker_container:
    state: absent
    name: "foo-container"

It's important to specify detach: false to capture the output, and then to use the ansible_facts.docker_container.Output path to access the results.

Answer 2

Don't use Ansible for running simple unit tests. Ansible makes complicated things easy and easy things complicated.

The following bash script is 4 lines and the Ansible playbook is already at 25 lines and still not fully functional due to concurrency issues and output formatting issues (I'm sure I'd find more).

Ansible for docker is still too new, doesn't deal easily with concurrency issues, has missing docker features, etc. and probably should only be used when you are doing something complicated that bash can't easily handle (like dealing with remote servers, retries, etc)

#!/bin/bash
docker build -t server-unit-test .
docker run -it --name server-unit-test server-unit-test npm test
docker rm server-unit-test