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molecule_demo

A "role" to demonstrate the power of Ansible Molecule

About

Molecule is pretty rad, so rad that Jeff Geerling is adopting it. It helps you develop Ansible roles by providing out of the box:

  • linting with yamlint
  • syntax checking with ansible-lint
  • test "scenarios" on docker, vagrant, ec2, and friends
  • infrastructure testing with testinfra
  • idempotence tests
  • side effect tests
  • a fuller head of hair

Overview

Here, we'll

  • Install Ansible Molecule
  • Create an Ansible Role
  • Run molecule's suite of tests
  • Create new scenarios, Including
    • testing in docker (the default)
    • testing in vagrant
    • testing in ec2

Watch a tutorial on asciicast

asciicast

Getting Started

Requirements

The main requirements are documented in requirements.txt but this demo assumes you have a few other things installed including

  • docker
  • vagrant
  • aws cli

Practice safe python. Create a virtualenv.

virtualenv venv --python=python3.7

Install the python requirements

pip install -r requirements.txt

Make sure Molecule is installed

$ molecule --help
Usage: molecule [OPTIONS] COMMAND [ARGS]...

   _____     _             _
  |     |___| |___ ___ _ _| |___
  | | | | . | | -_|  _| | | | -_|
  |_|_|_|___|_|___|___|___|_|___|

  Molecule aids in the development and testing of Ansible roles.

  Enable autocomplete issue:

    eval "$(_MOLECULE_COMPLETE=source molecule)"

Options:
  --debug / --no-debug    Enable or disable debug mode. Default is disabled.
  -c, --base-config TEXT  Path to a base config.  If provided Molecule will
                          load this config first, and deep merge each
                          scenario's molecule.yml on top.
                          (/Users/sblack/.config/molecule/config.yml)
  -e, --env-file TEXT     The file to read variables from when rendering
                          molecule.yml. (.env.yml)
  --version               Show the version and exit.
  --help                  Show this message and exit.

Commands:
  check        Use the provisioner to perform a Dry-Run...
  cleanup      Use the provisioner to cleanup any changes...
  converge     Use the provisioner to configure instances...
  create       Use the provisioner to start the instances.
  dependency   Manage the role's dependencies.
  destroy      Use the provisioner to destroy the instances.
  idempotence  Use the provisioner to configure the...
  init         Initialize a new role or scenario.
  lint         Lint the role.
  list         Lists status of instances.
  login        Log in to one instance.
  matrix       List matrix of steps used to test instances.
  prepare      Use the provisioner to prepare the instances...
  side-effect  Use the provisioner to perform side-effects...
  syntax       Use the provisioner to syntax check the role.
  test         Test (lint, destroy, dependency, syntax,...
  verify       Run automated tests against instances.

Create the role

Much like ansible-galaxy init molecule provides a nice template for new roles.

$ molecule init role -r molecule_demo
--> Initializing new role molecule_demo...
Initialized role in /Users/sblack/Git/rhythmic/molecule_demo successfully.

Run ALL the tests

$ molecule test
--> Validating schema /Users/sblack/Git/rhythmic/molecule_demo/molecule/default/molecule.yml.
Validation completed successfully.
--> Test matrix
    
└── default
    ├── lint
    ├── cleanup
    ├── destroy
    ├── dependency
    ├── syntax
    ├── create
    ├── prepare
    ├── converge
    ├── idempotence
    ├── side_effect
    ├── verify
    ├── cleanup
    └── destroy
    
--> Scenario: 'default'
--> Action: 'lint'
--> Executing Yamllint on files found in /Users/sblack/Git/rhythmic/molecule_demo/...
Lint completed successfully.
--> Executing Flake8 on files found in /Users/sblack/Git/rhythmic/molecule_demo/molecule/default/tests/...
Lint completed successfully.
--> Executing Ansible Lint on /Users/sblack/Git/rhythmic/molecule_demo/molecule/default/playbook.yml...
Lint completed successfully.
--> Scenario: 'default'
--> Action: 'cleanup'
Skipping, cleanup playbook not configured.
--> Scenario: 'default'
--> Action: 'destroy'
    
    PLAY [Destroy] *****************************************************************
    
    TASK [Destroy molecule instance(s)] ********************************************
    changed: [localhost] => (item=None)
    changed: [localhost]
    
    TASK [Wait for instance(s) deletion to complete] *******************************
    FAILED - RETRYING: Wait for instance(s) deletion to complete (300 retries left).
    ok: [localhost] => (item=None)
    ok: [localhost]
    
    TASK [Delete docker network(s)] ************************************************
    
    PLAY RECAP *********************************************************************
    localhost                  : ok=2    changed=1    unreachable=0    failed=0    skipped=1    rescued=0    ignored=0
    
    
--> Scenario: 'default'
--> Action: 'dependency'
Skipping, missing the requirements file.
--> Scenario: 'default'
--> Action: 'syntax'
    
    playbook: /Users/sblack/Git/rhythmic/molecule_demo/molecule/default/playbook.yml
    
--> Scenario: 'default'
--> Action: 'create'
[DEPRECATION WARNING]: docker_image_facts is kept for backwards compatibility 
but usage is discouraged. The module documentation details page may explain 
more about this rationale.. This feature will be removed in a future release. 
Deprecation warnings can be disabled by setting deprecation_warnings=False in 
ansible.cfg.
    
    PLAY [Create] ******************************************************************
    
    TASK [Log into a Docker registry] **********************************************
    skipping: [localhost] => (item=None) 
    
    TASK [Create Dockerfiles from image names] *************************************
    changed: [localhost] => (item=None)
    changed: [localhost]
    
    TASK [Discover local Docker images] ********************************************
    ok: [localhost] => (item=None)
    ok: [localhost]
    
    TASK [Build an Ansible compatible image] ***************************************
    ok: [localhost] => (item=None)
    ok: [localhost]
    
    TASK [Create docker network(s)] ************************************************
    
    TASK [Determine the CMD directives] ********************************************
    ok: [localhost] => (item=None)
    ok: [localhost]
    
    TASK [Create molecule instance(s)] *********************************************
    changed: [localhost] => (item=None)
    changed: [localhost]
    
    TASK [Wait for instance(s) creation to complete] *******************************
    FAILED - RETRYING: Wait for instance(s) creation to complete (300 retries left).
    changed: [localhost] => (item=None)
    changed: [localhost]
    
    PLAY RECAP *********************************************************************
    localhost                  : ok=6    changed=3    unreachable=0    failed=0    skipped=2    rescued=0    ignored=0
    
    
--> Scenario: 'default'
--> Action: 'prepare'
Skipping, prepare playbook not configured.
--> Scenario: 'default'
--> Action: 'converge'
    
    PLAY [Converge] ****************************************************************
    
    TASK [Gathering Facts] *********************************************************
    ok: [instance]
    
    TASK [molecule_demo : echo hello world] ****************************************
    ok: [instance] => {
        "msg": "hello world"
    }
    
    PLAY RECAP *********************************************************************
    instance                   : ok=2    changed=0    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0
    
    
--> Scenario: 'default'
--> Action: 'idempotence'
Idempotence completed successfully.
--> Scenario: 'default'
--> Action: 'side_effect'
Skipping, side effect playbook not configured.
--> Scenario: 'default'
--> Action: 'verify'
--> Executing Testinfra tests found in /Users/sblack/Git/rhythmic/molecule_demo/molecule/default/tests/...
    ============================= test session starts ==============================
    platform darwin -- Python 3.7.4, pytest-5.0.1, py-1.8.0, pluggy-0.12.0
    rootdir: /Users/sblack/Git/rhythmic/molecule_demo/molecule/default
    plugins: testinfra-3.0.5
collected 1 item 
    
    tests/test_default.py .                                                  [100%]
    
    =========================== 1 passed in 5.35 seconds ===========================
Verifier completed successfully.
--> Scenario: 'default'
--> Action: 'cleanup'
Skipping, cleanup playbook not configured.
--> Scenario: 'default'
--> Action: 'destroy'
    
    PLAY [Destroy] *****************************************************************
    
    TASK [Destroy molecule instance(s)] ********************************************
    changed: [localhost] => (item=None)
    changed: [localhost]
    
    TASK [Wait for instance(s) deletion to complete] *******************************
    FAILED - RETRYING: Wait for instance(s) deletion to complete (300 retries left).
    changed: [localhost] => (item=None)
    changed: [localhost]
    
    TASK [Delete docker network(s)] ************************************************
    
    PLAY RECAP *********************************************************************
    localhost                  : ok=2    changed=2    unreachable=0    failed=0    skipped=1    rescued=0    ignored=0

Run the role against our default test rig

$ molecule converge
--> Validating schema /Users/sblack/Git/rhythmic/molecule_demo/molecule/default/molecule.yml.
Validation completed successfully.
--> Test matrix
    
└── default
    ├── dependency
    ├── create
    ├── prepare
    └── converge
    
--> Scenario: 'default'
--> Action: 'dependency'
Skipping, missing the requirements file.
--> Scenario: 'default'
--> Action: 'create'
[DEPRECATION WARNING]: docker_image_facts is kept for backwards compatibility 
but usage is discouraged. The module documentation details page may explain 
more about this rationale.. This feature will be removed in a future release. 
Deprecation warnings can be disabled by setting deprecation_warnings=False in 
ansible.cfg.
    
    PLAY [Create] ******************************************************************
    
    TASK [Log into a Docker registry] **********************************************
    skipping: [localhost] => (item=None) 
    
    TASK [Create Dockerfiles from image names] *************************************
    changed: [localhost] => (item=None)
    changed: [localhost]
    
    TASK [Discover local Docker images] ********************************************
    ok: [localhost] => (item=None)
    ok: [localhost]
    
    TASK [Build an Ansible compatible image] ***************************************
    ok: [localhost] => (item=None)
    ok: [localhost]
    
    TASK [Create docker network(s)] ************************************************
    
    TASK [Determine the CMD directives] ********************************************
    ok: [localhost] => (item=None)
    ok: [localhost]
    
    TASK [Create molecule instance(s)] *********************************************
    changed: [localhost] => (item=None)
    changed: [localhost]
    
    TASK [Wait for instance(s) creation to complete] *******************************
    FAILED - RETRYING: Wait for instance(s) creation to complete (300 retries left).
    changed: [localhost] => (item=None)
    changed: [localhost]
    
    PLAY RECAP *********************************************************************
    localhost                  : ok=6    changed=3    unreachable=0    failed=0    skipped=2    rescued=0    ignored=0
    
    
--> Scenario: 'default'
--> Action: 'prepare'
Skipping, prepare playbook not configured.
--> Scenario: 'default'
--> Action: 'converge'
    
    PLAY [Converge] ****************************************************************
    
    TASK [Gathering Facts] *********************************************************
    ok: [instance]
    
    TASK [molecule_demo : echo hello world] ****************************************
    ok: [instance] => {
        "msg": "hello world"
    }
    
    PLAY RECAP *********************************************************************
    instance                   : ok=2    changed=0    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0

Now we can log in!

$ molecule login
--> Validating schema /Users/sblack/Git/rhythmic/molecule_demo/molecule/vagrant/molecule.yml.
Validation completed successfully.
--> Validating schema /Users/sblack/Git/rhythmic/molecule_demo/molecule/default/molecule.yml.
Validation completed successfully.
[root@instance /]#

Create a Vagrant Scenario and Run it!

This scenario is using the vagrant driver and

$ molecule init scenario -d vagrant -s vagrant
--> Initializing new scenario vagrant...
Initialized scenario in /Users/sblack/Git/rhythmic/molecule_demo/molecule/vagrant successfully.

Run it

$ molecule converge -s vagrant
....

Log in

$ molecule login -s vagrant
--> Validating schema /Users/sblack/Git/rhythmic/molecule_demo/molecule/vagrant/molecule.yml.
Validation completed successfully.
--> Validating schema /Users/sblack/Git/rhythmic/molecule_demo/molecule/default/molecule.yml.
Validation completed successfully.
Warning: Permanently added '[127.0.0.1]:2222' (ECDSA) to the list of known hosts.
Welcome to Ubuntu 16.04.6 LTS (GNU/Linux 4.4.0-157-generic x86_64)

 * Documentation:  https://help.ubuntu.com
 * Management:     https://landscape.canonical.com
 * Support:        https://ubuntu.com/advantage

13 packages can be updated.
9 updates are security updates.

New release '18.04.2 LTS' available.
Run 'do-release-upgrade' to upgrade to it.


Last login: Wed Aug 21 20:15:46 2019 from 10.0.2.2
vagrant@instance:~$

Again with ec2 as the driver

Create the Scenario

$ molecule init scenario -d ec2 -s ec2-scenario
- -> Initializing new scenario ec2-scenario...
Initialized scenario in /Users/sblack/Git/rhythmic/molecule_demo/molecule/ec2-scenario successfully.

Log in to AWS

$ aws_okta_login infraservices-admin
  • This is where I changed a few values in molecule/ec2-scenario/molecule.yml so that ansible would use the right image in the right subnet. The Ansible code used to spin up the ec2 instances is in molecule/ec2-scenario/create.yml.

Now we can run it!

$ molecule converge -s ec2-scenario
--> Validating schema /Users/sblack/Git/rhythmic/molecule_demo/molecule/ec2-scenario/molecule.yml.
Validation completed successfully.
--> Validating schema /Users/sblack/Git/rhythmic/molecule_demo/molecule/vagrant/molecule.yml.
Validation completed successfully.
--> Validating schema /Users/sblack/Git/rhythmic/molecule_demo/molecule/default/molecule.yml.
Validation completed successfully.
--> Test matrix
    
└── ec2-scenario
    ├── dependency
    ├── create
    ├── prepare
    └── converge
    
--> Scenario: 'ec2-scenario'
--> Action: 'dependency'
Skipping, missing the requirements file.
--> Scenario: 'ec2-scenario'
--> Action: 'create'
Skipping, instances already created.
--> Scenario: 'ec2-scenario'
--> Action: 'prepare'
Skipping, instances already prepared.
--> Scenario: 'ec2-scenario'
--> Action: 'converge'
    
    PLAY [Converge] ****************************************************************
    
    TASK [Gathering Facts] *********************************************************
    ok: [instance]
    
    TASK [molecule_demo : echo hello world] ****************************************
    ok: [instance] => {
        "msg": "hello world"
    }
    
    PLAY RECAP *********************************************************************
    instance                   : ok=2    changed=0    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0

And we can log in!

$ molecule login -s ec2-scenario
--> Validating schema /Users/sblack/Git/rhythmic/molecule_demo/molecule/ec2-scenario/molecule.yml.
Validation completed successfully.
--> Validating schema /Users/sblack/Git/rhythmic/molecule_demo/molecule/vagrant/molecule.yml.
Validation completed successfully.
--> Validating schema /Users/sblack/Git/rhythmic/molecule_demo/molecule/default/molecule.yml.
Validation completed successfully.
Warning: Permanently added '18.204.56.74' (ECDSA) to the list of known hosts.
Last login: Thu Aug 22 18:43:17 2019 from pool-108-51-226-95.washdc.fios.verizon.net

       __|  __|_  )
       _|  (     /   Amazon Linux 2 AMI
      ___|\___|___|

https://aws.amazon.com/amazon-linux-2/
5 package(s) needed for security, out of 13 available
Run "sudo yum update" to apply all updates.
[ec2-user@ip-172-31-71-132 ~]$

About

A Hello-World Ansible role to demonstrate the power of Molecule

Topics

ansible vagrant ec2 molecule rad asciicast ansible-roles molecule-demo

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