The Arch Linux DevOps team uses a combination of Ansible and Terraform to manage their hosts. If you want to have a look on their infrastructure repository, you can do so via this link: https://git.archlinux.org/infrastructure.git/tree/
The combination of Ansible and Terraform works quite well for Arch Linux, the only subject we are missing is proper testing. I want to present a small proof of concept on how we could do tests in the future. My approach uses molecule for testing. Molecule utilizes Vagrant and Docker for running the Ansible Playbooks.
The actual tests are written in Python with support of the library testinfra.
First of all we need to install the dependencies. You can find most of our needed tools in our repositories:
What we are missing right now is molecule. We can install molecule with the
vagrant dependencies via
pip install molecule[vagrant] --user. Pip will
install all needed packages to our $HOME.
So let us pick a first role we want to test:
❯ ls -la drwxr-xr-x - chris 15 Dec 2019 handlers drwxr-xr-x - chris 15 Dec 2019 tasks drwxr-xr-x - chris 15 Dec 2019 templates
We can initialize a molecule test scenario on an already existing Ansible role
molecule init scenario --role-name sshd --driver-name vagrant.
The command is going to create a
molecule directory for us. The created directory will have this structure:
❯ tree molecule molecule └── default ├── INSTALL.rst ├── molecule.yml ├── playbook.yml ├── prepare.yml └── tests ├── __pycache__ │ ├── test_default.cpython-38-pytest-5.3.5.pyc │ └── test_default.cpython-38.pyc └── test_default.py
The interesting files we will have a look at are
molecule.yml we configure basic molecule behavior.
prepare.yml we can do first preparations with Ansible (we need to do this,
because Arch Linux is slightly different to distributions the molecule team
test_default.py stores our tests as testinfra functions.
molecule.yml shouldn’t be so different for Arch Linux to the one that is usually generated by molecule, but let me highlight the changes:
--- dependency: name: galaxy driver: # We use Vagrant here, because we have other roles that need kernel modules etc name: vagrant provider: name: virtualbox lint: name: yamllint platforms: # Here we specify our official archlinux/archlinux image - name: instance box: archlinux/archlinux provisioner: name: ansible lint: name: ansible-lint # This option is important. The Ansible infrastructure roles use root on default. # So we need to gain privilege via sudo and become root for running all roles. connection_options: ansible_become: true verifier: name: testinfra lint: name: flake8
prepare.yml includes some magic, regarding mirror setup, installing python
and a fresh restart. We need this mirror setup tasks, because we are just
enabling all mirrors in our Arch Linux Vagrant box right now. This leads to
slow mirrors. I am going to
fix this in a new
Arch-Boxes release. For now I just set static mirrors from which I know that
they are fast for my location. In the second
prepare.yml task we need to
install python for Ansible. Consider that I use
pacman -Syu here, because I
want a full system upgrade, everything else will lead us into trouble when
playing around with kernel modules (Arch Linux provides still no nice way to
use kernel modules when you’ve installed a new kernel). Due to the full system
upgrade, we need to reboot for making sure that we boot into the new kernel.
--- - name: Prepare hosts: all gather_facts: false tasks: - name: Setup fast mirror raw: echo -e "Server = https://mirror.metalgamer.eu/archlinux/\$repo/os/\$arch\nServer = https://mirror.metalgamer.eu/archlinux/\$repo/os/\$arch\nhttps://ftp.spline.inf.fu-berlin.de/mirrors/archlinux/\$repo/os/\$arch" > /etc/pacman.d/mirrorlist become: true - name: Install python for Ansible raw: test -e /usr/bin/python || (pacman -Syu --noconfirm python) become: true changed_when: false - name: Reboot for kernel updates reboot:
The last important file is
test_default.py stores our unit
tests for the Ansible roles. Right now I am just checking for an installed
openssh package and a running and enabled
sshd daemon. The usage of
testinfra should be self-explanatory, however I didn’t make experience with
more complex tasks like comparing templates yet. I can imagine that this will
become very tedious for us. The future will show if the usage of testinfra
suits our demands. If not we either use a different library or we need to stay
with Ansible and YAML linting + tests on clean VMs or Docker containers. Both
of them would be already far better than the current situation with no tests at
import os import testinfra.utils.ansible_runner testinfra_hosts = testinfra.utils.ansible_runner.AnsibleRunner( os.environ['MOLECULE_INVENTORY_FILE'] ).get_hosts('all') def test_openssh_is_installed(host): openssh = host.package("openssh") assert openssh.is_installed def test_openssh_is_running_and_enabled(host): openssh = host.service("sshd") assert openssh.is_running assert openssh.is_enabled
For running our tests we can trigger
molecule test from inside of our sshd
role directory. I haven’t played around with
molecule converge yet, but I
guess this is the command you would use for local Ansible development.
molecule test will trigger a clean environment on every test (destroying the
VM snapshot etc). This is pretty cost intensive and takes time.
If you are interested in this work, you can follow my branch on github: