So You Want To Test Aws Modules For Ansible

17 Jul 2017

You’re a (prospective) contributor to Ansible, and you have some great improvements to make to an existing module or a brand new module. As a conscientious developer, you know that having tests will ensure that you don’t break existing behaviour, and that other people’s future enhancements won’t break your desired behaviour. The standard tests for AWS modules are integration tests as most of them rely on creating some resources in AWS, updating them, and then cleaning up afterwards.

I’ll start this post from absolute first principles - I’ll use a shiny new Fedora 26 vagrant VM.

Setting up Ansible for development

vagrant init fedora/26-cloud-base
vagrant up
vagrant ssh

The easiest way to ensure we have all the dependencies for Ansible installed is then to use dnf to install ansible.

sudo dnf install ansible

Next, clone the your fork of the source code for ansible:

ssh-keygen
eval `ssh-agent -s`
ssh-add
# Add the generated key to your github account
sudo dnf install git
git clone git@github.com:YOURUSER/ansible
cd ansible
git remote add upstream https://github.com/ansible/ansible
git pull upstream devel

Note that if you’re doing this on a host with any other ssh keys, it’s worth generating a github specific ssh key (using e.g. ssh-keygen -f ~/.ssh/github) and setting up your .ssh/config appropriately:

Host github.com
  IdentityFile ~/.ssh/github

At this point, ansible --version should give the released version of Ansible (at the time of writing, this was 2.3.1.0). To use the development version (not recommended for production use), do:

source hacking/env-setup

And ansible --version should now show the development version (currently 2.4.0)

Install docker

Add docker and set it up so that you don’t have to be root to run it. There are some security implications with this - being in the docker group is effectively equivalent to root access.

sudo dnf install docker
sudo groupadd docker
sudo gpasswd -a $USER docker
sudo systemctl restart docker
newgrp docker

Setting up AWS account

Install the relevant command line tools (you can do this in a virtualenv if you prefer - it depends if you’d need to test with different versions of boto3 etc). The boto library is currently still required for quite a few modules, as well as the common code used to connect to AWS.

pip install --user botocore boto3 boto awscli

Ensure you have an IAM administrative user with API access. DO NOT use this user for Ansible, or put its credentials anywhere near your git repo! I use boto profiles for all of the AWS accounts that I use, and don’t have a default profile so that I always have to choose.

Note: DO NOT use your AWS root user - if you don’t have a suitable user yet, create a new IAM user with the AdministratorAccess managed policy (or similar) attached

Ensure a profile for this IAM user exists in ~/.aws/credentials and then run:

export ADMIN_PROFILE=$your_profile_name
ansible-playbook hacking/aws_config/setup-iam.yml -e iam_group=ansible_test -e profile=$ADMIN_PROFILE -e region=us-east-2 -vv

You don’t actually have to set profile or region at all if you don’t need them - region defaults to us-east-1, but you can only choose us-east-2 as an alternative at this time.

You’ll now need to go into AWS console, create an IAM user (called e.g. ansible_test) and make them a member of the newly created group (ansible_test if you used that with iam_group in While you’re there, create an API credential for the test user. This can all be automated:

aws iam create-user --user-name ansible_test --profile $ADMIN_PROFILE
aws iam add-user-to-group --user-name ansible_test --group_name ansible_test --profile $ADMIN_PROFILE
aws iam create-access-key --user-name ansible_test --profile $ADMIN_PROFILE

Note: This can be done through Ansible’s iam module too. It’s just simpler to document the steps with the CLI as they fit on three lines rather than one very long ansible adhoc command line or a larger ansible playbook.

Using the information from the new credential, you can do:

cp test/integration/cloud-config-aws.yml.template test/integration/cloud-config-aws.yml

and then update that file to include this new secret key and access key. It’s also worth adding the following for region if you’re not using us-east-1


aws_region: us-east-2
ec2_region: "{{ aws_region }}"

Note: The credentials in ~/.aws/credentials and cloud-config-aws.yml should be completely different. A good way to test this is:

aws sts get-caller-identity --profile=$ADMIN_PROFILE

ansible -m shell -a 'AWS_SECRET_ACCESS_KEY={{ aws_secret_key }} AWS_ACCESS_KEY_ID={{ aws_access_key }} aws sts get-caller-identity' \
  -e @test/integration/cloud-config-aws.yml localhost

The first of these should return your administrator user. The second of these should return your Ansible test user. If this isn’t the case, check the previous steps (and let me know if I can improve the documentation!).

Running an integration test suite

Check that you can run the integration tests

ansible-test integration --docker -v ec2_group

The first run will be quite slow as you need to pull down all the required containers. Future runs will be much quicker, particularly if you pass --docker-no-pull to speed things up (it’s worth updating the containers fairly regularly, of course)

Writing your own tests

For your module, you will need:

meta/main.yml

- dependencies:
  - prepare_tests
  - setup_ec2

These are needed to ensure that resource_prefix is available to your tests. All resources are expected to be prefixed with this to ensure that they can be cleaned up more easily.

aliases

cloud/aws
posix/ci/cloud/aws

Without the aliases file, the cloud-config-aws.yml doesn’t get picked up.

tasks/main.yml

This should contain all of the tasks needed for the tests. Most actions are coupled with an assert task that the test has had the desired effect.

The main tasks should be in a block with an accompanying always that cleans up to avoid things being left behind by the tests


- block:
  - name: create resource
    aws_module:
      state: present
      name: "{{ resource_prefix }}-more-name"
      ...
    register: aws_module_result

  - name: check that resource was created
    assert:
      that:
        - aws_module_result.changed
        - aws_module_result.name == "{{ resource_prefix }}-more-name"
    ...

- always:
  - name: remove resource
    aws_module:
      state: absent
      name: "{{ resource_prefix }}-more-name"
      ...

Things worth checking

Troubleshooting

While docker is quite useful for quickly running tests and cleaning up after itself, occasionally you might need to get the debugger out to see why your module isn’t doing what you expect.

At this point, it’s likely easiest to create a quick test playbook

- hosts: localhost
  vars_files:
  - test/integration/cloud-config-aws.yml

  roles:
  - test/integration/targets/aws_module

And run this with ANSIBLE_KEEP_REMOTE_FILES=1 ansible-playbook test-playbook.yml -vvv. You can then follow the ansible debugging instructions.

I tend to use epdb to put in a breakpoint where the module is going wrong (or before the module has gone wrong) and analyse from there.

So my steps are:

  1. python /path/to/module explode
  2. cd /path/to/debug_dir
  3. Edit ansible_module_module_name.py, add import epdb; epdb.st() at the relevant location
  4. python /path/to/module execute
  5. python -c 'import epdb; epdb.connect()'

Tidy up

Detach the policies from your test IAM group - this will leave the test group and user in place but with zero privileges.

export GROUP=$your_iam_group
for policy_arn in `aws iam list-attached-group-policies --group-name $GROUP --profile $ADMIN_PROFILE --query 'AttachedPolicies[].PolicyArn' --output text`
do aws iam detach-group-policy --group-name $GROUP --policy-arn $policy_arn --profile $ADMIN_PROFILE
done

Shut down docker and vagrant

sudo systemctl stop docker
exit
vagrant halt

Conclusion

This post is designed to assist people with setting up the various steps needed to test and debug AWS modules for Ansible. There are almost certainly errors, omissions, and things that I could learn to do better.

If you have any suggestions for improvement, please raise an issue or PR on https://github.com/willthames/willthames.github.io or just let me know on Twitter or email (links below). Thanks!

Thanks

Thanks to Moritz Grimm for pointing out a couple of typos. These are now fixed.