Windows module development walkthrough

Windows module development walkthrough

In this section, we will walk through developing, testing, and debugging anAnsible Windows module.

Because Windows modules are written in Powershell and need to be run on aWindows host, this guide differs from the usual development walkthrough guide.

What’s covered in this section:

Windows environment setup

Unlike Python module development which can be run on the host that runsAnsible, Windows modules need to be written and tested for Windows hosts.While evaluation editions of Windows can be downloaded fromMicrosoft, these images are usually not ready to be used by Ansible withoutfurther modification. The easiest way to set up a Windows host so that it isready to by used by Ansible is to set up a virtual machine using Vagrant.Vagrant can be used to download existing OS images called boxes that are thendeployed to a hypervisor like VirtualBox. These boxes can either be created andstored offline or they can be downloaded from a central repository calledVagrant Cloud.

This guide will use the Vagrant boxes created by the packer-windozerepository which have also been uploaded to Vagrant Cloud.To find out more info on how these images are created, please go to the Githubrepo and look at the README file.

Before you can get started, the following programs must be installed (please consult the Vagrant andVirtualBox documentation for installation instructions):

Vagrant
VirtualBox

Create a Windows server in a VM

To create a single Windows Server 2016 instance, run the following:

vagrant init jborean93/WindowsServer2016
vagrant up

This will download the Vagrant box from Vagrant Cloud and add it to the localboxes on your host and then start up that instance in VirtualBox. When startingfor the first time, the Windows VM will run through the sysprep process andthen create a HTTP and HTTPS WinRM listener automatically. Vagrant will finishits process once the listeners are onlinem, after which the VM can be used by Ansible.

Create an Ansible inventory

The following Ansible inventory file can be used to connect to the newlycreated Windows VM:

[windows]
WindowsServer  ansible_host=127.0.0.1
 
[windows:vars]
ansible_user=vagrant
ansible_password=vagrant
ansible_port=55986
ansible_connection=winrm
ansible_winrm_transport=ntlm
ansible_winrm_server_cert_validation=ignore

Note

The port 55986 is automatically forwarded by Vagrant to theWindows host that was created, if this conflicts with an existing localport then Vagrant will automatically use another one at random and displayshow that in the output.

The OS that is created is based on the image set. The followingimages can be used:

When the host is online, it can accessible by RDP on 127.0.0.1:3389 but theport may differ depending if there was a conflict. To get rid of the host, runvagrant destroy —force and Vagrant will automatically remove the VM andany other files associated with that VM.

While this is useful when testing modules on a single Windows instance, thesehost won’t work without modification with domain based modules. The Vagrantfileat ansible-windowscan be used to create a test domain environment to be used in Ansible. Thisrepo contains three files which are used by both Ansible and Vagrant to createmultiple Windows hosts in a domain environment. These files are:

Vagrantfile: The Vagrant file that reads the inventory setup of inventory.yml and provisions the hosts that are required
inventory.yml: Contains the hosts that are required and other connection information such as IP addresses and forwarded ports
main.yml: Ansible playbook called by Vagrant to provision the domain controller and join the child hosts to the domain

By default, these files will create the following environment:

A single domain controller running on Windows Server 2016
Five child hosts for each major Windows Server version joined to that domain
A domain with the DNS name domain.local
A local administrator account on each host with the username vagrant and password vagrant
A domain admin account vagrant-domain@domain.local with the password VagrantPass1

The domain name and accounts can be modified by changing the variablesdomain_* in the inventory.yml file if it is required. The inventoryfile can also be modified to provision more or less servers by changing thehosts that are defined under the domain_children key. The host variableansible_host is the private IP that will be assigned to the VirtualBox hostonly network adapter while vagrant_box is the box that will be used tocreate the VM.

Provisioning the environment

To provision the environment as is, run the following:

git clone https://github.com/jborean93/ansible-windows.git
cd vagrant
vagrant up

Note

Vagrant provisions each host sequentially so this can take some timeto complete. If any errors occur during the Ansible phase of setting up thedomain, run vagrant provision to rerun just that step.

Unlike setting up a single Windows instance with Vagrant, these hosts can alsobe accessed using the IP address directly as well as through the forwardedports. It is easier to access it over the host only network adapter as thenormal protocol ports are used, e.g. RDP is still over 3389. In cases wherethe host cannot be resolved using the host only network IP, the followingprotocols can be access over 127.0.0.1 using these forwarded ports:

RDP: 295xx
SSH: 296xx
WinRM HTTP: 297xx
WinRM HTTPS: 298xx
SMB: 299xx

Replace xx with the entry number in the inventory file where the domaincontroller started with 00 and is incremented from there. For example, inthe default inventory.yml file, WinRM over HTTPS for SERVER2012R2 isforwarded over port 29804 as it’s the fourth entry in domain_children.

Note

While an SSH server is available on all Windows hosts but Server2008 (non R2), it is not a support connection for Ansible managing Windowshosts and should not be used with Ansible.

Windows new module development

When creating a new module there are a few things to keep in mind:

Module code is in Powershell (.ps1) files while the documentation is contained in Python (.py) files of the same name
Avoid using Write-Host/Debug/Verbose/Error in the module and add what needs to be returned to the $result variable
When trying an exception use Fail-Json -obj $result -message "exception message here" instead
Most new modules require check mode and integration tests before they are merged into the main Ansible codebase
Avoid using try/catch statements over a large code block, rather use them for individual calls so the error message can be more descriptive
Try and catch specific exceptions when using try/catch statements
Avoid using PSCustomObjects unless necessary
Look for common functions in ./lib/ansible/module_utils/powershell/ and use the code there instead of duplicating work. These can be imported by adding the line #Requires -Module where is the filename to import, and will be automatically included with the module code sent to the Windows target when run via Ansible
Ensure the code runs under Powershell v3 and higher on Windows Server 2008 and higher; if higher minimum Powershell or OS versions are required, ensure the documentation reflects this clearly
Ansible runs modules under strictmode version 2.0. Be sure to test with that enabled by putting Set-StrictMode -Version 2.0 at the top of your dev script
Favour native Powershell cmdlets over executable calls if possible
If adding an object to $result, ensure any trailing slashes are removed or escaped, as ConvertTo-Json will fail to convert it
Use the full cmdlet name instead of aliases, e.g. Remove-Item over rm
Use named parameters with cmdlets, e.g. Remove-Item -Path C:\temp over Remove-Item C:\temp

A very basic powershell module win_environment is included below. It demonstrates how to implement check-mode and diff-support, and also shows a warning to the user when a specific condition is met.

#!powershell
 
# Copyright: (c) 2015, Jon Hawkesworth (@jhawkesworth) <[email protected]>
# GNU General Public License v3.0+ (see COPYING or https://www.gnu.org/licenses/gpl-3.0.txt)
 
#Requires -Module Ansible.ModuleUtils.Legacy
 
$ErrorActionPreference = "Stop"
 
$params = Parse-Args -arguments $args -supports_check_mode $true
$check_mode = Get-AnsibleParam -obj $params -name "_ansible_check_mode" -type "bool" -default $false
$diff_mode = Get-AnsibleParam -obj $params -name "_ansible_diff" -type "bool" -default $false
 
$name = Get-AnsibleParam -obj $params -name "name" -type "str" -failifempty $true
$state = Get-AnsibleParam -obj $params -name "state" -type "str" -default "present" -validateset "absent","present"
$value = Get-AnsibleParam -obj $params -name "value" -type "str"
$level = Get-AnsibleParam -obj $params -name "level" -type "str" -validateSet "machine","user","process" -failifempty $true
 
$before_value = [Environment]::GetEnvironmentVariable($name, $level)
 
$result = @{
    before_value = $before_value
    changed = $false
    value = $value
}
 
# When removing environment, set value to $null if set
if ($state -eq "absent" -and $value) {
    Add-Warning -obj $result -message "When removing environment variable '$name' it should not have a value '$value' set"
    $value = $null
} elseif ($state -eq "present" -and (-not $value)) {
    Fail-Json -obj $result -message "When state=present, value must be defined and not an empty string, if you wish to remove the envvar, set state=absent"
}
 
if ($state -eq "present" -and $before_value -ne $value) {
 
    if (-not $check_mode) {
        [Environment]::SetEnvironmentVariable($name, $value, $level)
    }
    $result.changed = $true
 
    if ($diff_mode) {
        if ($before_value -eq $null) {
            $result.diff = @{
                prepared = " [$level]`n+$name = $value`n"
            }
        } else {
            $result.diff = @{
                prepared = " [$level]`n-$name = $before_value`n+$name = $value`n"
            }
        }
    }
 
} elseif ($state -eq "absent" -and $before_value -ne $null) {
 
    if (-not $check_mode) {
        [Environment]::SetEnvironmentVariable($name, $null, $level)
    }
    $result.changed = $true
 
    if ($diff_mode) {
        $result.diff = @{
            prepared = " [$level]`n-$name = $before_value`n"
        }
    }
 
}
 
Exit-Json -obj $result

A slightly more advanced module is win_uri which additionally shows how to use different parameter types (bool, str, int, list, dict, path) and a selection of choices for parameters, how to fail a module and how to handle exceptions.

When in doubt, look at some of the other core modules and see how things have beenimplemented there.

Sometimes there are multiple ways that Windows offers to complete a task; thisis the order to favour when writing modules:

Native Powershell cmdlets like Remove-Item -Path C:\temp -Recurse
.NET classes like [System.IO.Path]::GetRandomFileName()
WMI objects through the New-CimInstance cmdlet
COM objects through New-Object -ComObject cmdlet
Calls to native executables like Secedit.exe

PowerShell modules support a small subset of the #Requires options builtinto PowerShell as well as some Ansible-specific requirements specified by#AnsibleRequires. These statements can be placed at any point in the script,but are most commonly near the top. They are used to make it easier to state therequirements of the module without writing any of the checks. Each requiresstatement must be on its own line, but there can be multiple requires statementsin one script.

These are the checks that can be used within Ansible modules:

#Requires -Module Ansible.ModuleUtils.<module_util>: Added in Ansible 2.4, specifies a module_util to load in for the module execution.
#Requires -Version x.y: Added in Ansible 2.5, specifies the version of PowerShell that is required by the module. The module will fail if this requirement is not met.
#AnsibleRequires -OSVersion x.y: Added in Ansible 2.5, specifies the OS build version that is required by the module and will fail if this requirement is not met. The actual OS version is derived from [Environment]::OSVersion.Version.
#AnsibleRequires -Become: Added in Ansible 2.5, forces the exec runner to run the module with become, which is primarily used to bypass WinRM restrictions. If ansible_become_user is not specified then the SYSTEM account is used instead.

Windows module utilities

Like Python modules, PowerShell modules also provide a number of moduleutilities that provide helper functions within PowerShell. These module_utilscan be imported by adding the following line to a PowerShell module:

#Requires -Module Ansible.ModuleUtils.Legacy

This will import the module_util at ./lib/ansible/module_utils/powershell/Ansible.ModuleUtils.Legacy.psm1and enable calling all of its functions.

The following is a list of module_utils that are packaged with Ansible and a general description of whatthey do:

ArgvParser: Utiliy used to convert a list of arguments to an escaped string compliant with the Windows argument parsing rules.
CamelConversion: Utility used to convert camelCase strings/lists/dicts to snake_case.
CommandUtil: Utility used to execute a Windows process and return the stdout/stderr and rc as separate objects.
FileUtil: Utility that expands on the Get-ChildItem and Test-Path to work with special files like C:\pagefile.sys.
Legacy: General definitions and helper utilities for Ansible module.
LinkUtil: Utility to create, remove, and get information about symbolic links, junction points and hard inks.
SID: Utilities used to convert a user or group to a Windows SID and vice versa.

For more details on any specific module utility and their requirements, please see the Ansiblemodule utilities source code.

PowerShell module utilities can be stored outside of the standard Ansibledistribution for use with custom modules. Custom module_utils are placed in afolder called module_utils located in the root folder of the playbook or roledirectory.

The below example is a role structure that contains two custom module_utilscalled Ansible.ModuleUtils.ModuleUtil1 andAnsible.ModuleUtils.ModuleUtil2:

meta/
  main.yml
defaults/
  main.yml
module_utils/
  Ansible.ModuleUtils.ModuleUtil1.psm1
  Ansible.ModuleUtils.ModuleUtil2.psm1
tasks/
  main.yml

Each module_util must contain at least one function, and a list of functions, aliases and cmdlets to export for usein a module. This can be a blanket export by using *. For example:

Export-ModuleMember -Alias * -Function * -Cmdlet *

Windows playbook module testing

You can test a module with an Ansible playbook. For example:

Create a playbook in any directory touch testmodule.yml.
Create an inventory file in the same directory touch hosts.
Populate the inventory file with the variables required to connect to a Windows host(s).
Add the following to the new playbook file:

---
- name: test out windows module
  hosts: windows
  tasks:
  - name: test out module
    win_module:
      name: test name

Run the playbook ansible-playbook -i hosts testmodule.yml

This can be useful for seeing how Ansible runs withthe new module end to end. Other possible ways to test the module areshown below.

Windows debugging

Debugging a module currently can only be done on a Windows host. This can beuseful when developing a new module or implementing bug fixes. Theseare some steps that need to be followed to set this up:

Copy the module script to the Windows server
Copy ./lib/ansible/module_utils/powershell/Ansible.ModuleUtils.Legacy.psm1 to the same directory as the script above
To stop the script from exiting the editor on a successful run, in Ansible.ModuleUtils.Legacy.psm1 under the function Exit-Json, replace the last two lines of the function with:

ConvertTo-Json -InputObject $obj -Depth 99

To stop the script from exiting the editor on a failed run, in Ansible.ModuleUtils.Legacy.psm1 under the function Fail-Json, replace the last two lines of the function with:

Write-Error -Message (ConvertTo-Json -InputObject $obj -Depth 99)

Add the following to the start of the module script that was copied to the server:

### start setup code
$complex_args = @{
    "_ansible_check_mode" = $false
    "_ansible_diff" = $false
    "path" = "C:\temp"
    "state" = "present"
}
 
Import-Module -Name .\Ansible.ModuleUtils.Legacy.psm1
### end setup code

You can add more args to $complex_args as required by the module. Themodule can now be run on the Windows host either directly through Powershellor through an IDE.

There are multiple IDEs that can be used to debug a Powershell script, two ofthe most popular are

To be able to view the arguments as passed by Ansible to the module followthese steps.

Prefix the Ansible command with ANSIBLE_KEEP_REMOTE_FILES=1 to specify that Ansible should keep the exec files on the server.
Log onto the Windows server using the same user account that Ansible used to execute the module.
Navigate to %TEMP%... It should contain a folder starting with ansible-tmp-.
Inside this folder, open the PowerShell script for the module.
In this script is a raw JSON script under $json_raw which contains the module arguments under module_args. These args can be assigned manually to the $complex_args variable that is defined on your debug script.

Windows unit testing

Currently there is no mechanism to run unit tests for Powershell modules under Ansible CI.

Windows integration testing

Integration tests for Ansible modules are typically written as Ansible roles. These testroles are located in ./test/integration/targets. You must first set up your testingenvironment, and configure a test inventory for Ansible to connect to.

In this example we will set up a test inventory to connect to two hosts and run the integrationtests for win_stat:

Create a copy of ./test/integration/inventory.winrm.template and name it inventory.winrm.
Fill in entries under [windows] and set the required variables that are needed to connect to the host.
To execute the integration tests, run ansible-test windows-integration win_stat; you can replace win_stat with the role you wish to test.

This will execute all the tests currently defined for that role. You can setthe verbosity level using the -v argument just as you would withansible-playbook.

When developing tests for a new module, it is recommended to test a scenario once incheck mode and twice not in check mode. This ensures that check modedoes not make any changes but reports a change, as well as that the second run isidempotent and does not report changes. For example:

- name: remove a file (check mode)
  win_file:
    path: C:\temp
    state: absent
  register: remove_file_check
  check_mode: yes
 
- name: get result of remove a file (check mode)
  win_command: powershell.exe "if (Test-Path -Path 'C:\temp') { 'true' } else { 'false' }"
  register: remove_file_actual_check
 
- name: assert remove a file (check mode)
  assert:
    that:
    - remove_file_check is changed
    - remove_file_actual_check.stdout == 'true\r\n'
 
- name: remove a file
  win_file:
    path: C:\temp
    state: absent
  register: remove_file
 
- name: get result of remove a file
  win_command: powershell.exe "if (Test-Path -Path 'C:\temp') { 'true' } else { 'false' }"
  register: remove_file_actual
 
- name: assert remove a file
  assert:
    that:
    - remove_file is changed
    - remove_file_actual.stdout == 'false\r\n'
 
- name: remove a file (idempotent)
  win_file:
    path: C:\temp
    state: absent
  register: remove_file_again
 
- name: assert remove a file (idempotent)
  assert:
    that:
    - not remove_file_again is changed

Windows communication and development support

Join the IRC channel #ansible-devel or #ansible-windows on freenode fordiscussions about Ansible development for Windows.

For questions and discussions pertaining to using the Ansible product,use the #ansible channel.